[libgpiod,1/3] licensing: make the project REUSE-compliant

diff --git a/.gitignore b/.gitignore
index a77efde..2d7cc7f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 *.o
 *.lo
 *.la
diff --git a/COPYING b/COPYING
index 5522aa5..aa85945 100644
--- a/COPYING
+++ b/COPYING
@@ -1,508 +1,23 @@ 
+libgpiod is provided under:
 
-                  GNU LESSER GENERAL PUBLIC LICENSE
-                       Version 2.1, February 1999
+    SPDX-License-Identifier: LGPL-2.1-or-later
 
- Copyright (C) 1991, 1999 Free Software Foundation, Inc.
-	51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
+Being under the terms of the GNU Lesser General Public License version 2.1
+or any later version according with:
 
-[This is the first released version of the Lesser GPL.  It also counts
- as the successor of the GNU Library Public License, version 2, hence
- the version number 2.1.]
+    LICENSES/LGPL-2.1.txt
 
-                            Preamble
+The Linux Kernel uAPI headers are provided under:
 
-  The licenses for most software are designed to take away your
-freedom to share and change it.  By contrast, the GNU General Public
-Licenses are intended to guarantee your freedom to share and change
-free software--to make sure the software is free for all its users.
+    SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note
 
-  This license, the Lesser General Public License, applies to some
-specially designated software packages--typically libraries--of the
-Free Software Foundation and other authors who decide to use it.  You
-can use it too, but we suggest you first think carefully about whether
-this license or the ordinary General Public License is the better
-strategy to use in any particular case, based on the explanations
-below.
+Being under the terms of the GNU General Public License version 2 only,
+according with:
 
-  When we speak of free software, we are referring to freedom of use,
-not price.  Our General Public Licenses are designed to make sure that
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+    LICENSES/GPL-2.0.txt
 
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+With an explicit syscall exception, as stated at:
 
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+    LICENSES/Linux-syscall-note.txt
 
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diff --git a/Doxyfile.in b/Doxyfile.in
index be2d250..22d4721 100644
--- a/Doxyfile.in
+++ b/Doxyfile.in
@@ -1,10 +1,5 @@ 
-# SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 # libgpiod doxygen configuration
 
diff --git a/LICENSES/CC-BY-SA-4.0.txt b/LICENSES/CC-BY-SA-4.0.txt
new file mode 100644
index 0000000..3b7b82d
--- /dev/null
+++ b/LICENSES/CC-BY-SA-4.0.txt
@@ -0,0 +1,427 @@ 
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+     copyright--then that use is not regulated by the license. Our
+     licenses grant only permissions under copyright and certain
+     other rights that a licensor has authority to grant. Use of
+     the licensed material may still be restricted for other
+     reasons, including because others have copyright or other
+     rights in the material. A licensor may make special requests,
+     such as asking that all changes be marked or described.
+     Although not required by our licenses, you are encouraged to
+     respect those requests where reasonable. More_considerations
+     for the public:
+	wiki.creativecommons.org/Considerations_for_licensees
+
+=======================================================================
+
+Creative Commons Attribution-ShareAlike 4.0 International Public
+License
+
+By exercising the Licensed Rights (defined below), You accept and agree
+to be bound by the terms and conditions of this Creative Commons
+Attribution-ShareAlike 4.0 International Public License ("Public
+License"). To the extent this Public License may be interpreted as a
+contract, You are granted the Licensed Rights in consideration of Your
+acceptance of these terms and conditions, and the Licensor grants You
+such rights in consideration of benefits the Licensor receives from
+making the Licensed Material available under these terms and
+conditions.
+
+
+Section 1 -- Definitions.
+
+  a. Adapted Material means material subject to Copyright and Similar
+     Rights that is derived from or based upon the Licensed Material
+     and in which the Licensed Material is translated, altered,
+     arranged, transformed, or otherwise modified in a manner requiring
+     permission under the Copyright and Similar Rights held by the
+     Licensor. For purposes of this Public License, where the Licensed
+     Material is a musical work, performance, or sound recording,
+     Adapted Material is always produced where the Licensed Material is
+     synched in timed relation with a moving image.
+
+  b. Adapter's License means the license You apply to Your Copyright
+     and Similar Rights in Your contributions to Adapted Material in
+     accordance with the terms and conditions of this Public License.
+
+  c. BY-SA Compatible License means a license listed at
+     creativecommons.org/compatiblelicenses, approved by Creative
+     Commons as essentially the equivalent of this Public License.
+
+  d. Copyright and Similar Rights means copyright and/or similar rights
+     closely related to copyright including, without limitation,
+     performance, broadcast, sound recording, and Sui Generis Database
+     Rights, without regard to how the rights are labeled or
+     categorized. For purposes of this Public License, the rights
+     specified in Section 2(b)(1)-(2) are not Copyright and Similar
+     Rights.
+
+  e. Effective Technological Measures means those measures that, in the
+     absence of proper authority, may not be circumvented under laws
+     fulfilling obligations under Article 11 of the WIPO Copyright
+     Treaty adopted on December 20, 1996, and/or similar international
+     agreements.
+
+  f. Exceptions and Limitations means fair use, fair dealing, and/or
+     any other exception or limitation to Copyright and Similar Rights
+     that applies to Your use of the Licensed Material.
+
+  g. License Elements means the license attributes listed in the name
+     of a Creative Commons Public License. The License Elements of this
+     Public License are Attribution and ShareAlike.
+
+  h. Licensed Material means the artistic or literary work, database,
+     or other material to which the Licensor applied this Public
+     License.
+
+  i. Licensed Rights means the rights granted to You subject to the
+     terms and conditions of this Public License, which are limited to
+     all Copyright and Similar Rights that apply to Your use of the
+     Licensed Material and that the Licensor has authority to license.
+
+  j. Licensor means the individual(s) or entity(ies) granting rights
+     under this Public License.
+
+  k. Share means to provide material to the public by any means or
+     process that requires permission under the Licensed Rights, such
+     as reproduction, public display, public performance, distribution,
+     dissemination, communication, or importation, and to make material
+     available to the public including in ways that members of the
+     public may access the material from a place and at a time
+     individually chosen by them.
+
+  l. Sui Generis Database Rights means rights other than copyright
+     resulting from Directive 96/9/EC of the European Parliament and of
+     the Council of 11 March 1996 on the legal protection of databases,
+     as amended and/or succeeded, as well as other essentially
+     equivalent rights anywhere in the world.
+
+  m. You means the individual or entity exercising the Licensed Rights
+     under this Public License. Your has a corresponding meaning.
+
+
+Section 2 -- Scope.
+
+  a. License grant.
+
+       1. Subject to the terms and conditions of this Public License,
+          the Licensor hereby grants You a worldwide, royalty-free,
+          non-sublicensable, non-exclusive, irrevocable license to
+          exercise the Licensed Rights in the Licensed Material to:
+
+            a. reproduce and Share the Licensed Material, in whole or
+               in part; and
+
+            b. produce, reproduce, and Share Adapted Material.
+
+       2. Exceptions and Limitations. For the avoidance of doubt, where
+          Exceptions and Limitations apply to Your use, this Public
+          License does not apply, and You do not need to comply with
+          its terms and conditions.
+
+       3. Term. The term of this Public License is specified in Section
+          6(a).
+
+       4. Media and formats; technical modifications allowed. The
+          Licensor authorizes You to exercise the Licensed Rights in
+          all media and formats whether now known or hereafter created,
+          and to make technical modifications necessary to do so. The
+          Licensor waives and/or agrees not to assert any right or
+          authority to forbid You from making technical modifications
+          necessary to exercise the Licensed Rights, including
+          technical modifications necessary to circumvent Effective
+          Technological Measures. For purposes of this Public License,
+          simply making modifications authorized by this Section 2(a)
+          (4) never produces Adapted Material.
+
+       5. Downstream recipients.
+
+            a. Offer from the Licensor -- Licensed Material. Every
+               recipient of the Licensed Material automatically
+               receives an offer from the Licensor to exercise the
+               Licensed Rights under the terms and conditions of this
+               Public License.
+
+            b. Additional offer from the Licensor -- Adapted Material.
+               Every recipient of Adapted Material from You
+               automatically receives an offer from the Licensor to
+               exercise the Licensed Rights in the Adapted Material
+               under the conditions of the Adapter's License You apply.
+
+            c. No downstream restrictions. You may not offer or impose
+               any additional or different terms or conditions on, or
+               apply any Effective Technological Measures to, the
+               Licensed Material if doing so restricts exercise of the
+               Licensed Rights by any recipient of the Licensed
+               Material.
+
+       6. No endorsement. Nothing in this Public License constitutes or
+          may be construed as permission to assert or imply that You
+          are, or that Your use of the Licensed Material is, connected
+          with, or sponsored, endorsed, or granted official status by,
+          the Licensor or others designated to receive attribution as
+          provided in Section 3(a)(1)(A)(i).
+
+  b. Other rights.
+
+       1. Moral rights, such as the right of integrity, are not
+          licensed under this Public License, nor are publicity,
+          privacy, and/or other similar personality rights; however, to
+          the extent possible, the Licensor waives and/or agrees not to
+          assert any such rights held by the Licensor to the limited
+          extent necessary to allow You to exercise the Licensed
+          Rights, but not otherwise.
+
+       2. Patent and trademark rights are not licensed under this
+          Public License.
+
+       3. To the extent possible, the Licensor waives any right to
+          collect royalties from You for the exercise of the Licensed
+          Rights, whether directly or through a collecting society
+          under any voluntary or waivable statutory or compulsory
+          licensing scheme. In all other cases the Licensor expressly
+          reserves any right to collect such royalties.
+
+
+Section 3 -- License Conditions.
+
+Your exercise of the Licensed Rights is expressly made subject to the
+following conditions.
+
+  a. Attribution.
+
+       1. If You Share the Licensed Material (including in modified
+          form), You must:
+
+            a. retain the following if it is supplied by the Licensor
+               with the Licensed Material:
+
+                 i. identification of the creator(s) of the Licensed
+                    Material and any others designated to receive
+                    attribution, in any reasonable manner requested by
+                    the Licensor (including by pseudonym if
+                    designated);
+
+                ii. a copyright notice;
+
+               iii. a notice that refers to this Public License;
+
+                iv. a notice that refers to the disclaimer of
+                    warranties;
+
+                 v. a URI or hyperlink to the Licensed Material to the
+                    extent reasonably practicable;
+
+            b. indicate if You modified the Licensed Material and
+               retain an indication of any previous modifications; and
+
+            c. indicate the Licensed Material is licensed under this
+               Public License, and include the text of, or the URI or
+               hyperlink to, this Public License.
+
+       2. You may satisfy the conditions in Section 3(a)(1) in any
+          reasonable manner based on the medium, means, and context in
+          which You Share the Licensed Material. For example, it may be
+          reasonable to satisfy the conditions by providing a URI or
+          hyperlink to a resource that includes the required
+          information.
+
+       3. If requested by the Licensor, You must remove any of the
+          information required by Section 3(a)(1)(A) to the extent
+          reasonably practicable.
+
+  b. ShareAlike.
+
+     In addition to the conditions in Section 3(a), if You Share
+     Adapted Material You produce, the following conditions also apply.
+
+       1. The Adapter's License You apply must be a Creative Commons
+          license with the same License Elements, this version or
+          later, or a BY-SA Compatible License.
+
+       2. You must include the text of, or the URI or hyperlink to, the
+          Adapter's License You apply. You may satisfy this condition
+          in any reasonable manner based on the medium, means, and
+          context in which You Share Adapted Material.
+
+       3. You may not offer or impose any additional or different terms
+          or conditions on, or apply any Effective Technological
+          Measures to, Adapted Material that restrict exercise of the
+          rights granted under the Adapter's License You apply.
+
+
+Section 4 -- Sui Generis Database Rights.
+
+Where the Licensed Rights include Sui Generis Database Rights that
+apply to Your use of the Licensed Material:
+
+  a. for the avoidance of doubt, Section 2(a)(1) grants You the right
+     to extract, reuse, reproduce, and Share all or a substantial
+     portion of the contents of the database;
+
+  b. if You include all or a substantial portion of the database
+     contents in a database in which You have Sui Generis Database
+     Rights, then the database in which You have Sui Generis Database
+     Rights (but not its individual contents) is Adapted Material,
+
+     including for purposes of Section 3(b); and
+  c. You must comply with the conditions in Section 3(a) if You Share
+     all or a substantial portion of the contents of the database.
+
+For the avoidance of doubt, this Section 4 supplements and does not
+replace Your obligations under this Public License where the Licensed
+Rights include other Copyright and Similar Rights.
+
+
+Section 5 -- Disclaimer of Warranties and Limitation of Liability.
+
+  a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE
+     EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS
+     AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF
+     ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS,
+     IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION,
+     WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR
+     PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS,
+     ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT
+     KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT
+     ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.
+
+  b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE
+     TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION,
+     NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT,
+     INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES,
+     COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR
+     USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN
+     ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR
+     DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR
+     IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.
+
+  c. The disclaimer of warranties and limitation of liability provided
+     above shall be interpreted in a manner that, to the extent
+     possible, most closely approximates an absolute disclaimer and
+     waiver of all liability.
+
+
+Section 6 -- Term and Termination.
+
+  a. This Public License applies for the term of the Copyright and
+     Similar Rights licensed here. However, if You fail to comply with
+     this Public License, then Your rights under this Public License
+     terminate automatically.
+
+  b. Where Your right to use the Licensed Material has terminated under
+     Section 6(a), it reinstates:
+
+       1. automatically as of the date the violation is cured, provided
+          it is cured within 30 days of Your discovery of the
+          violation; or
+
+       2. upon express reinstatement by the Licensor.
+
+     For the avoidance of doubt, this Section 6(b) does not affect any
+     right the Licensor may have to seek remedies for Your violations
+     of this Public License.
+
+  c. For the avoidance of doubt, the Licensor may also offer the
+     Licensed Material under separate terms or conditions or stop
+     distributing the Licensed Material at any time; however, doing so
+     will not terminate this Public License.
+
+  d. Sections 1, 5, 6, 7, and 8 survive termination of this Public
+     License.
+
+
+Section 7 -- Other Terms and Conditions.
+
+  a. The Licensor shall not be bound by any additional or different
+     terms or conditions communicated by You unless expressly agreed.
+
+  b. Any arrangements, understandings, or agreements regarding the
+     Licensed Material not stated herein are separate from and
+     independent of the terms and conditions of this Public License.
+
+
+Section 8 -- Interpretation.
+
+  a. For the avoidance of doubt, this Public License does not, and
+     shall not be interpreted to, reduce, limit, restrict, or impose
+     conditions on any use of the Licensed Material that could lawfully
+     be made without permission under this Public License.
+
+  b. To the extent possible, if any provision of this Public License is
+     deemed unenforceable, it shall be automatically reformed to the
+     minimum extent necessary to make it enforceable. If the provision
+     cannot be reformed, it shall be severed from this Public License
+     without affecting the enforceability of the remaining terms and
+     conditions.
+
+  c. No term or condition of this Public License will be waived and no
+     failure to comply consented to unless expressly agreed to by the
+     Licensor.
+
+  d. Nothing in this Public License constitutes or may be interpreted
+     as a limitation upon, or waiver of, any privileges and immunities
+     that apply to the Licensor or You, including from the legal
+     processes of any jurisdiction or authority.
+
+
+=======================================================================
+
+Creative Commons is not a party to its public
+licenses. Notwithstanding, Creative Commons may elect to apply one of
+its public licenses to material it publishes and in those instances
+will be considered the “Licensor.” The text of the Creative Commons
+public licenses is dedicated to the public domain under the CC0 Public
+Domain Dedication. Except for the limited purpose of indicating that
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+public licenses.
+
+Creative Commons may be contacted at creativecommons.org.
diff --git a/LICENSES/GPL-2.0-only.txt b/LICENSES/GPL-2.0-only.txt
new file mode 100644
index 0000000..d159169
--- /dev/null
+++ b/LICENSES/GPL-2.0-only.txt
@@ -0,0 +1,339 @@ 
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
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+want its recipients to know that what they have is not the original, so
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+
+  Finally, any free program is threatened constantly by software
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+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
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+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
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+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
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+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
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+    notice that there is no warranty (or else, saying that you provide
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+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
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+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
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+exercise the right to control the distribution of derivative or
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+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
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+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
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+    years, to give any third party, for a charge no more than your
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+
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+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
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+distribution of the source code, even though third parties are not
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+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
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+prohibited by law if you do not accept this License.  Therefore, by
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+all its terms and conditions for copying, distributing or modifying
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+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
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+these terms and conditions.  You may not impose any further
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+You are not responsible for enforcing compliance by third parties to
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+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
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+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
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+
+It is not the purpose of this section to induce you to infringe any
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+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
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diff --git a/LICENSES/GPL-2.0-or-later.txt b/LICENSES/GPL-2.0-or-later.txt
new file mode 120000
index 0000000..0a87fbd
--- /dev/null
+++ b/LICENSES/GPL-2.0-or-later.txt
@@ -0,0 +1 @@ 
+GPL-2.0-only.txt
\ No newline at end of file
diff --git a/LICENSES/LGPL-2.1-or-later.txt b/LICENSES/LGPL-2.1-or-later.txt
new file mode 100644
index 0000000..e5ab03e
--- /dev/null
+++ b/LICENSES/LGPL-2.1-or-later.txt
@@ -0,0 +1,502 @@ 
+                  GNU LESSER GENERAL PUBLIC LICENSE
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+"copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the library's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Lesser General Public
+    License as published by the Free Software Foundation; either
+    version 2.1 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public
+    License along with this library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+Also add information on how to contact you by electronic and paper mail.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the library, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the
+  library `Frob' (a library for tweaking knobs) written by James Random Hacker.
+
+  <signature of Ty Coon>, 1 April 1990
+  Ty Coon, President of Vice
+
+That's all there is to it!
diff --git a/LICENSES/Linux-syscall-note.txt b/LICENSES/Linux-syscall-note.txt
new file mode 100644
index 0000000..9abdad7
--- /dev/null
+++ b/LICENSES/Linux-syscall-note.txt
@@ -0,0 +1,25 @@ 
+SPDX-Exception-Identifier: Linux-syscall-note
+SPDX-URL: https://spdx.org/licenses/Linux-syscall-note.html
+SPDX-Licenses: GPL-2.0, GPL-2.0+, GPL-1.0+, LGPL-2.0, LGPL-2.0+, LGPL-2.1, LGPL-2.1+, GPL-2.0-only, GPL-2.0-or-later
+Usage-Guide:
+  This exception is used together with one of the above SPDX-Licenses
+  to mark user space API (uapi) header files so they can be included
+  into non GPL compliant user space application code.
+  To use this exception add it with the keyword WITH to one of the
+  identifiers in the SPDX-Licenses tag:
+    SPDX-License-Identifier: <SPDX-License> WITH Linux-syscall-note
+License-Text:
+
+   NOTE! This copyright does *not* cover user programs that use kernel
+ services by normal system calls - this is merely considered normal use
+ of the kernel, and does *not* fall under the heading of "derived work".
+ Also note that the GPL below is copyrighted by the Free Software
+ Foundation, but the instance of code that it refers to (the Linux
+ kernel) is copyrighted by me and others who actually wrote it.
+
+ Also note that the only valid version of the GPL as far as the kernel
+ is concerned is _this_ particular version of the license (ie v2, not
+ v2.2 or v3.x or whatever), unless explicitly otherwise stated.
+
+			Linus Torvalds
+
diff --git a/Makefile.am b/Makefile.am
index b67312f..203c291 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,15 +1,16 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2019 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 ACLOCAL_AMFLAGS = -I m4
 AUTOMAKE_OPTIONS = foreign
 SUBDIRS = include lib
 
+EXTRA_DIST = \
+	LICENSES/CC-BY-SA-4.0.txt \
+	LICENSES/GPL-2.0-only.txt \
+	LICENSES/LGPL-2.1-or-later.txt \
+	LICENSES/Linux-syscall-note.txt
+
 if WITH_TOOLS
 
 SUBDIRS += tools man
@@ -35,6 +36,6 @@  doc: Doxyfile
 clean-local:
 	rm -rf doc
 
-EXTRA_DIST = Doxyfile
+EXTRA_DIST += Doxyfile
 
 endif
diff --git a/NEWS b/NEWS
index d367ee8..c843c3c 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: CC-BY-SA-4.0
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 libgpiod v1.6
 =============
 
diff --git a/README b/README
index 5d29157..814a0f1 100644
--- a/README
+++ b/README
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: CC-BY-SA-4.0
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 libgpiod
 ========
 
diff --git a/TODO b/TODO
index c7cae8e..b4fe991 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: CC-BY-SA-4.0
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 TODO list for libgpiod
 
 ==========
diff --git a/autogen.sh b/autogen.sh
index 1da6874..7d21070 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -1,12 +1,7 @@ 
 #!/bin/sh
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#                    2017 Thierry Reding <treding@nvidia.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+# SPDX-FileCopyrightText: 2017 Thierry Reding <treding@nvidia.com>
 
 srcdir=`dirname $0`
 test -z "$srcdir" && srcdir=.
diff --git a/bindings/Makefile.am b/bindings/Makefile.am
index 24e2c98..c5301f9 100644
--- a/bindings/Makefile.am
+++ b/bindings/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 SUBDIRS = .
 
diff --git a/bindings/cxx/Makefile.am b/bindings/cxx/Makefile.am
index 87463b0..23c03f4 100644
--- a/bindings/cxx/Makefile.am
+++ b/bindings/cxx/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 lib_LTLIBRARIES = libgpiodcxx.la
 libgpiodcxx_la_SOURCES = chip.cpp iter.cpp line.cpp line_bulk.cpp
diff --git a/bindings/cxx/chip.cpp b/bindings/cxx/chip.cpp
index 59351dd..49c5602 100644
--- a/bindings/cxx/chip.cpp
+++ b/bindings/cxx/chip.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <functional>
 #include <gpiod.hpp>
diff --git a/bindings/cxx/examples/.gitignore b/bindings/cxx/examples/.gitignore
index acb5791..54bda46 100644
--- a/bindings/cxx/examples/.gitignore
+++ b/bindings/cxx/examples/.gitignore
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 gpiodetectcxx
 gpiofindcxx
 gpiogetcxx
diff --git a/bindings/cxx/examples/Makefile.am b/bindings/cxx/examples/Makefile.am
index 43e9875..bdd951d 100644
--- a/bindings/cxx/examples/Makefile.am
+++ b/bindings/cxx/examples/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 AM_CPPFLAGS = -I$(top_srcdir)/bindings/cxx/ -I$(top_srcdir)/include
 AM_CPPFLAGS += -Wall -Wextra -g -std=gnu++17
diff --git a/bindings/cxx/examples/gpiodetectcxx.cpp b/bindings/cxx/examples/gpiodetectcxx.cpp
index 76d367d..84dff9d 100644
--- a/bindings/cxx/examples/gpiodetectcxx.cpp
+++ b/bindings/cxx/examples/gpiodetectcxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* C++ reimplementation of the gpiodetect tool. */
 
diff --git a/bindings/cxx/examples/gpiofindcxx.cpp b/bindings/cxx/examples/gpiofindcxx.cpp
index f8b771c..cafcbb1 100644
--- a/bindings/cxx/examples/gpiofindcxx.cpp
+++ b/bindings/cxx/examples/gpiofindcxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* C++ reimplementation of the gpiofind tool. */
 
diff --git a/bindings/cxx/examples/gpiogetcxx.cpp b/bindings/cxx/examples/gpiogetcxx.cpp
index d565a43..486ff57 100644
--- a/bindings/cxx/examples/gpiogetcxx.cpp
+++ b/bindings/cxx/examples/gpiogetcxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Simplified C++ reimplementation of the gpioget tool. */
 
diff --git a/bindings/cxx/examples/gpioinfocxx.cpp b/bindings/cxx/examples/gpioinfocxx.cpp
index 384286e..76b7bc1 100644
--- a/bindings/cxx/examples/gpioinfocxx.cpp
+++ b/bindings/cxx/examples/gpioinfocxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Simplified C++ reimplementation of the gpioinfo tool. */
 
diff --git a/bindings/cxx/examples/gpiomoncxx.cpp b/bindings/cxx/examples/gpiomoncxx.cpp
index 75bd715..6b199c4 100644
--- a/bindings/cxx/examples/gpiomoncxx.cpp
+++ b/bindings/cxx/examples/gpiomoncxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Simplified C++ reimplementation of the gpiomon tool. */
 
diff --git a/bindings/cxx/examples/gpiosetcxx.cpp b/bindings/cxx/examples/gpiosetcxx.cpp
index 5c0b8c9..fb093cb 100644
--- a/bindings/cxx/examples/gpiosetcxx.cpp
+++ b/bindings/cxx/examples/gpiosetcxx.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Simplified C++ reimplementation of the gpioset tool. */
 
diff --git a/bindings/cxx/gpiod.hpp b/bindings/cxx/gpiod.hpp
index 9028822..84669e7 100644
--- a/bindings/cxx/gpiod.hpp
+++ b/bindings/cxx/gpiod.hpp
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 #ifndef __LIBGPIOD_GPIOD_CXX_HPP__
 #define __LIBGPIOD_GPIOD_CXX_HPP__
diff --git a/bindings/cxx/iter.cpp b/bindings/cxx/iter.cpp
index 846d36b..0d7e90a 100644
--- a/bindings/cxx/iter.cpp
+++ b/bindings/cxx/iter.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <gpiod.hpp>
 #include <system_error>
diff --git a/bindings/cxx/libgpiodcxx.pc.in b/bindings/cxx/libgpiodcxx.pc.in
index 9d227c9..731227c 100644
--- a/bindings/cxx/libgpiodcxx.pc.in
+++ b/bindings/cxx/libgpiodcxx.pc.in
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 prefix=@prefix@
 exec_prefix=@exec_prefix@
 libdir=@libdir@
diff --git a/bindings/cxx/line.cpp b/bindings/cxx/line.cpp
index 9b66d1a..d24df18 100644
--- a/bindings/cxx/line.cpp
+++ b/bindings/cxx/line.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <gpiod.hpp>
 #include <array>
@@ -337,7 +333,7 @@  void line::throw_if_null(void) const
 line::chip_guard::chip_guard(const line& line)
 	: _m_chip(line._m_owner)
 {
-	
+
 }
 
 } /* namespace gpiod */
diff --git a/bindings/cxx/line_bulk.cpp b/bindings/cxx/line_bulk.cpp
index 17b7208..b31efb5 100644
--- a/bindings/cxx/line_bulk.cpp
+++ b/bindings/cxx/line_bulk.cpp
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <gpiod.hpp>
 #include <map>
diff --git a/bindings/cxx/tests/.gitignore b/bindings/cxx/tests/.gitignore
index 580672e..7990193 100644
--- a/bindings/cxx/tests/.gitignore
+++ b/bindings/cxx/tests/.gitignore
@@ -1 +1,4 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 gpiod-cxx-test
diff --git a/bindings/cxx/tests/Makefile.am b/bindings/cxx/tests/Makefile.am
index 5fa8f95..3599c02 100644
--- a/bindings/cxx/tests/Makefile.am
+++ b/bindings/cxx/tests/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 AM_CPPFLAGS = -I$(top_srcdir)/bindings/cxx/ -I$(top_srcdir)/include
 AM_CPPFLAGS += -I$(top_srcdir)/tests/mockup/
diff --git a/bindings/cxx/tests/gpio-mockup.cpp b/bindings/cxx/tests/gpio-mockup.cpp
index e8db962..54e69b7 100644
--- a/bindings/cxx/tests/gpio-mockup.cpp
+++ b/bindings/cxx/tests/gpio-mockup.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <system_error>
 
diff --git a/bindings/cxx/tests/gpio-mockup.hpp b/bindings/cxx/tests/gpio-mockup.hpp
index 38fb649..7a071fb 100644
--- a/bindings/cxx/tests/gpio-mockup.hpp
+++ b/bindings/cxx/tests/gpio-mockup.hpp
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 #ifndef __GPIOD_CXX_TEST_HPP__
 #define __GPIOD_CXX_TEST_HPP__
diff --git a/bindings/cxx/tests/gpiod-cxx-test-main.cpp b/bindings/cxx/tests/gpiod-cxx-test-main.cpp
index 5494bee..7343c1a 100644
--- a/bindings/cxx/tests/gpiod-cxx-test-main.cpp
+++ b/bindings/cxx/tests/gpiod-cxx-test-main.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #define CATCH_CONFIG_MAIN
 #include <catch2/catch.hpp>
diff --git a/bindings/cxx/tests/gpiod-cxx-test.cpp b/bindings/cxx/tests/gpiod-cxx-test.cpp
index 373ba10..1f1f20f 100644
--- a/bindings/cxx/tests/gpiod-cxx-test.cpp
+++ b/bindings/cxx/tests/gpiod-cxx-test.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <linux/version.h>
 #include <sys/utsname.h>
diff --git a/bindings/cxx/tests/tests-chip.cpp b/bindings/cxx/tests/tests-chip.cpp
index 1b16b65..bf4db0d 100644
--- a/bindings/cxx/tests/tests-chip.cpp
+++ b/bindings/cxx/tests/tests-chip.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <catch2/catch.hpp>
 #include <gpiod.hpp>
diff --git a/bindings/cxx/tests/tests-event.cpp b/bindings/cxx/tests/tests-event.cpp
index 97ea670..25cccde 100644
--- a/bindings/cxx/tests/tests-event.cpp
+++ b/bindings/cxx/tests/tests-event.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <catch2/catch.hpp>
 #include <gpiod.hpp>
diff --git a/bindings/cxx/tests/tests-iter.cpp b/bindings/cxx/tests/tests-iter.cpp
index 0dee754..11243c9 100644
--- a/bindings/cxx/tests/tests-iter.cpp
+++ b/bindings/cxx/tests/tests-iter.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <catch2/catch.hpp>
 #include <gpiod.hpp>
diff --git a/bindings/cxx/tests/tests-line.cpp b/bindings/cxx/tests/tests-line.cpp
index e201b99..01f785d 100644
--- a/bindings/cxx/tests/tests-line.cpp
+++ b/bindings/cxx/tests/tests-line.cpp
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <catch2/catch.hpp>
 #include <gpiod.hpp>
diff --git a/bindings/python/Makefile.am b/bindings/python/Makefile.am
index 5403bcb..fd4092d 100644
--- a/bindings/python/Makefile.am
+++ b/bindings/python/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 pyexec_LTLIBRARIES = gpiod.la
 
diff --git a/bindings/python/examples/Makefile.am b/bindings/python/examples/Makefile.am
index a0e06c0..c9bee28 100644
--- a/bindings/python/examples/Makefile.am
+++ b/bindings/python/examples/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 EXTRA_DIST =				\
 		gpiodetect.py		\
diff --git a/bindings/python/examples/gpiodetect.py b/bindings/python/examples/gpiodetect.py
index 781939b..665f07a 100755
--- a/bindings/python/examples/gpiodetect.py
+++ b/bindings/python/examples/gpiodetect.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Reimplementation of the gpiodetect tool in Python.'''
 
diff --git a/bindings/python/examples/gpiofind.py b/bindings/python/examples/gpiofind.py
index 2655742..74aff8e 100755
--- a/bindings/python/examples/gpiofind.py
+++ b/bindings/python/examples/gpiofind.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Reimplementation of the gpiofind tool in Python.'''
 
diff --git a/bindings/python/examples/gpioget.py b/bindings/python/examples/gpioget.py
index bdff23d..6cff18b 100755
--- a/bindings/python/examples/gpioget.py
+++ b/bindings/python/examples/gpioget.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Simplified reimplementation of the gpioget tool in Python.'''
 
diff --git a/bindings/python/examples/gpioinfo.py b/bindings/python/examples/gpioinfo.py
index 1593337..238e04c 100755
--- a/bindings/python/examples/gpioinfo.py
+++ b/bindings/python/examples/gpioinfo.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Simplified reimplementation of the gpioinfo tool in Python.'''
 
diff --git a/bindings/python/examples/gpiomon.py b/bindings/python/examples/gpiomon.py
index 1c56176..891760e 100755
--- a/bindings/python/examples/gpiomon.py
+++ b/bindings/python/examples/gpiomon.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Simplified reimplementation of the gpiomon tool in Python.'''
 
diff --git a/bindings/python/examples/gpioset.py b/bindings/python/examples/gpioset.py
index 3e7b121..947e916 100755
--- a/bindings/python/examples/gpioset.py
+++ b/bindings/python/examples/gpioset.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 '''Simplified reimplementation of the gpioset tool in Python.'''
 
diff --git a/bindings/python/gpiodmodule.c b/bindings/python/gpiodmodule.c
index 02514cc..91b0c04 100644
--- a/bindings/python/gpiodmodule.c
+++ b/bindings/python/gpiodmodule.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <Python.h>
 #include <gpiod.h>
diff --git a/bindings/python/tests/Makefile.am b/bindings/python/tests/Makefile.am
index 9030e7b..7c8bb5e 100644
--- a/bindings/python/tests/Makefile.am
+++ b/bindings/python/tests/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 dist_bin_SCRIPTS = gpiod_py_test.py
 
diff --git a/bindings/python/tests/gpiod_py_test.py b/bindings/python/tests/gpiod_py_test.py
index 324f5e3..a1e22e8 100755
--- a/bindings/python/tests/gpiod_py_test.py
+++ b/bindings/python/tests/gpiod_py_test.py
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env python3
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 import errno
 import gpiod
diff --git a/bindings/python/tests/gpiomockupmodule.c b/bindings/python/tests/gpiomockupmodule.c
index d54ecf9..761d431 100644
--- a/bindings/python/tests/gpiomockupmodule.c
+++ b/bindings/python/tests/gpiomockupmodule.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <Python.h>
 #include <gpio-mockup.h>
diff --git a/configure.ac b/configure.ac
index f6db096..32b50a8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2019 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 AC_PREREQ([2.69])
 
diff --git a/include/Makefile.am b/include/Makefile.am
index dc1afa9..dcbfde0 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1,9 +1,4 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 include_HEADERS = gpiod.h
diff --git a/include/gpiod.h b/include/gpiod.h
index 532f70a..76aa1dd 100644
--- a/include/gpiod.h
+++ b/include/gpiod.h
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 #ifndef __LIBGPIOD_GPIOD_H__
 #define __LIBGPIOD_GPIOD_H__
diff --git a/lib/Makefile.am b/lib/Makefile.am
index fb0dae9..1bc86e0 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 lib_LTLIBRARIES = libgpiod.la
 libgpiod_la_SOURCES = core.c helpers.c misc.c uapi/gpio.h
diff --git a/lib/core.c b/lib/core.c
index d015567..077ea3e 100644
--- a/lib/core.c
+++ b/lib/core.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Low-level, core library code. */
 
diff --git a/lib/helpers.c b/lib/helpers.c
index ac6325d..0071a2d 100644
--- a/lib/helpers.c
+++ b/lib/helpers.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /*
  * More specific variants of the core API and misc functions that don't need
diff --git a/lib/libgpiod.pc.in b/lib/libgpiod.pc.in
index 48ff113..913859a 100644
--- a/lib/libgpiod.pc.in
+++ b/lib/libgpiod.pc.in
@@ -1,3 +1,7 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+# SPDX-FileCopyrightText: 2018 Clemens Gruber <clemens.gruber@pqgruber.com>
+
 prefix=@prefix@
 exec_prefix=@exec_prefix@
 libdir=@libdir@
diff --git a/lib/misc.c b/lib/misc.c
index b812416..5583eb0 100644
--- a/lib/misc.c
+++ b/lib/misc.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Misc code that didn't fit anywhere else. */
 
diff --git a/lib/uapi/gpio.h b/lib/uapi/gpio.h
index b8d2687..eaaea3d 100644
--- a/lib/uapi/gpio.h
+++ b/lib/uapi/gpio.h
@@ -1,4 +1,4 @@ 
-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
 /*
  * <linux/gpio.h> - userspace ABI for the GPIO character devices
  *
@@ -8,8 +8,8 @@ 
  * under the terms of the GNU General Public License version 2 as published by
  * the Free Software Foundation.
  */
-#ifndef _GPIO_H_
-#define _GPIO_H_
+#ifndef _UAPI_GPIO_H_
+#define _UAPI_GPIO_H_
 
 #include <linux/const.h>
 #include <linux/ioctl.h>
@@ -65,6 +65,7 @@  struct gpiochip_info {
  * @GPIO_V2_LINE_FLAG_BIAS_PULL_UP: line has pull-up bias enabled
  * @GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN: line has pull-down bias enabled
  * @GPIO_V2_LINE_FLAG_BIAS_DISABLED: line has bias disabled
+ * @GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME: line events contain REALTIME timestamps
  */
 enum gpio_v2_line_flag {
 	GPIO_V2_LINE_FLAG_USED			= _BITULL(0),
@@ -78,6 +79,7 @@  enum gpio_v2_line_flag {
 	GPIO_V2_LINE_FLAG_BIAS_PULL_UP		= _BITULL(8),
 	GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN	= _BITULL(9),
 	GPIO_V2_LINE_FLAG_BIAS_DISABLED		= _BITULL(10),
+	GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME	= _BITULL(11),
 };
 
 /**
@@ -210,7 +212,7 @@  struct gpio_v2_line_request {
  * @offset: the local offset on this GPIO chip, fill this in when
  * requesting the line information from the kernel
  * @num_attrs: the number of attributes in @attrs
- * @flags: flags for the GPIO lines, with values from &enum
+ * @flags: flags for this GPIO line, with values from &enum
  * gpio_v2_line_flag, such as %GPIO_V2_LINE_FLAG_ACTIVE_LOW,
  * %GPIO_V2_LINE_FLAG_OUTPUT etc, added together.
  * @attrs: the configuration attributes associated with the line
@@ -270,9 +272,6 @@  enum gpio_v2_line_event_id {
 /**
  * struct gpio_v2_line_event - The actual event being pushed to userspace
  * @timestamp_ns: best estimate of time of event occurrence, in nanoseconds.
- * The @timestamp_ns is read from %CLOCK_MONOTONIC and is intended to allow
- * the accurate measurement of the time between events. It does not provide
- * the wall-clock time.
  * @id: event identifier with value from &enum gpio_v2_line_event_id
  * @offset: the offset of the line that triggered the event
  * @seqno: the sequence number for this event in the sequence of events for
@@ -280,6 +279,13 @@  enum gpio_v2_line_event_id {
  * @line_seqno: the sequence number for this event in the sequence of
  * events on this particular line
  * @padding: reserved for future use
+ *
+ * By default the @timestamp_ns is read from %CLOCK_MONOTONIC and is
+ * intended to allow the accurate measurement of the time between events.
+ * It does not provide the wall-clock time.
+ *
+ * If the %GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME flag is set then the
+ * @timestamp_ns is read from %CLOCK_REALTIME.
  */
 struct gpio_v2_line_event {
 	__aligned_u64 timestamp_ns;
@@ -519,4 +525,4 @@  struct gpioevent_data {
 #define GPIOHANDLE_SET_CONFIG_IOCTL _IOWR(0xB4, 0x0A, struct gpiohandle_config)
 #define GPIO_GET_LINEINFO_WATCH_IOCTL _IOWR(0xB4, 0x0B, struct gpioline_info)
 
-#endif /* _GPIO_H_ */
+#endif /* _UAPI_GPIO_H_ */
diff --git a/man/.gitignore b/man/.gitignore
index 900429f..1263cf7 100644
--- a/man/.gitignore
+++ b/man/.gitignore
@@ -1 +1,4 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 *.man
diff --git a/man/Makefile.am b/man/Makefile.am
index 0f9c644..c6d589f 100644
--- a/man/Makefile.am
+++ b/man/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 if WITH_MANPAGES
 
diff --git a/man/template b/man/template
index f1040ff..7ce5415 100644
--- a/man/template
+++ b/man/template
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: CC-BY-SA-4.0
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 [AUTHOR]
 Bartosz Golaszewski <bartekgola@gmail.com>
 
diff --git a/tests/.gitignore b/tests/.gitignore
index 703dc7c..676f092 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -1 +1,4 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 gpiod-test
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 91798f7..04fa3b2 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 SUBDIRS = mockup
 
diff --git a/tests/gpiod-test.c b/tests/gpiod-test.c
index 343e836..46249a7 100644
--- a/tests/gpiod-test.c
+++ b/tests/gpiod-test.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <glib/gstdio.h>
diff --git a/tests/gpiod-test.h b/tests/gpiod-test.h
index 7ed4d23..9b9e4ba 100644
--- a/tests/gpiod-test.h
+++ b/tests/gpiod-test.h
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 /*
  * Testing framework for the core library.
diff --git a/tests/mockup/Makefile.am b/tests/mockup/Makefile.am
index d3449cc..af29a95 100644
--- a/tests/mockup/Makefile.am
+++ b/tests/mockup/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 lib_LTLIBRARIES = libgpiomockup.la
 
diff --git a/tests/mockup/gpio-mockup.c b/tests/mockup/gpio-mockup.c
index 5e85819..eba26d3 100644
--- a/tests/mockup/gpio-mockup.c
+++ b/tests/mockup/gpio-mockup.c
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <libkmod.h>
diff --git a/tests/mockup/gpio-mockup.h b/tests/mockup/gpio-mockup.h
index b04dafa..4a55032 100644
--- a/tests/mockup/gpio-mockup.h
+++ b/tests/mockup/gpio-mockup.h
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 #ifndef __GPIO_MOCKUP_H__
 #define __GPIO_MOCKUP_H__
diff --git a/tests/tests-bulk.c b/tests/tests-bulk.c
index 22cae84..d079003 100644
--- a/tests/tests-bulk.c
+++ b/tests/tests-bulk.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2020 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 
diff --git a/tests/tests-chip.c b/tests/tests-chip.c
index c18bd5d..6713565 100644
--- a/tests/tests-chip.c
+++ b/tests/tests-chip.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 
diff --git a/tests/tests-event.c b/tests/tests-event.c
index 5fa4459..a213bf0 100644
--- a/tests/tests-event.c
+++ b/tests/tests-event.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <unistd.h>
diff --git a/tests/tests-line.c b/tests/tests-line.c
index 2bfb8b4..8de1e6a 100644
--- a/tests/tests-line.c
+++ b/tests/tests-line.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <string.h>
diff --git a/tests/tests-misc.c b/tests/tests-misc.c
index d077d49..a98329f 100644
--- a/tests/tests-misc.c
+++ b/tests/tests-misc.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <string.h>
 
diff --git a/tools/.gitignore b/tools/.gitignore
index 33bc931..0d53de9 100644
--- a/tools/.gitignore
+++ b/tools/.gitignore
@@ -1,3 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
+
 gpiodetect
 gpioinfo
 gpioget
diff --git a/tools/Makefile.am b/tools/Makefile.am
index b08bc3b..bbfcab6 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -1,10 +1,5 @@ 
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 AM_CFLAGS = -I$(top_srcdir)/include/ -include $(top_builddir)/config.h
 AM_CFLAGS += -Wall -Wextra -g -std=gnu89
diff --git a/tools/gpio-tools-test b/tools/gpio-tools-test
index 1b9f9a1..7d42374 100755
--- a/tools/gpio-tools-test
+++ b/tools/gpio-tools-test
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env bash
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 MIN_KERNEL_VERSION="5.5.0"
 BATS_SCRIPT="gpio-tools-test.bats"
diff --git a/tools/gpio-tools-test.bats b/tools/gpio-tools-test.bats
index ec39046..ba0a904 100755
--- a/tools/gpio-tools-test.bats
+++ b/tools/gpio-tools-test.bats
@@ -1,11 +1,6 @@ 
 #!/usr/bin/env bats
 # SPDX-License-Identifier: LGPL-2.1-or-later
-
-#
-# This file is part of libgpiod.
-#
-# Copyright (C) 2019 Bartosz Golaszewski <bgolaszewski@baylibre.com>
-#
+# SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 # Simple test harness for the gpio-tools.
 
diff --git a/tools/gpiodetect.c b/tools/gpiodetect.c
index 6f94f91..1780f40 100644
--- a/tools/gpiodetect.c
+++ b/tools/gpiodetect.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <dirent.h>
 #include <errno.h>
diff --git a/tools/gpiofind.c b/tools/gpiofind.c
index 3760ada..45033d9 100644
--- a/tools/gpiofind.c
+++ b/tools/gpiofind.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <dirent.h>
 #include <errno.h>
diff --git a/tools/gpioget.c b/tools/gpioget.c
index efbacce..0d8e286 100644
--- a/tools/gpioget.c
+++ b/tools/gpioget.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <getopt.h>
 #include <gpiod.h>
diff --git a/tools/gpioinfo.c b/tools/gpioinfo.c
index 729b179..aba5bde 100644
--- a/tools/gpioinfo.c
+++ b/tools/gpioinfo.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <dirent.h>
 #include <errno.h>
diff --git a/tools/gpiomon.c b/tools/gpiomon.c
index 3586cb4..e9f2055 100644
--- a/tools/gpiomon.c
+++ b/tools/gpiomon.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <getopt.h>
diff --git a/tools/gpioset.c b/tools/gpioset.c
index 20a7d3b..b34efea 100644
--- a/tools/gpioset.c
+++ b/tools/gpioset.c
@@ -1,9 +1,5 @@ 
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 #include <errno.h>
 #include <gpiod.h>
diff --git a/tools/tools-common.c b/tools/tools-common.c
index 9d4612a..98a4b9d 100644
--- a/tools/tools-common.c
+++ b/tools/tools-common.c
@@ -1,9 +1,5 @@ 
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+// SPDX-License-Identifier: LGPL-2.1-or-later
+// SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com>
 
 /* Common code for GPIO tools. */
 
diff --git a/tools/tools-common.h b/tools/tools-common.h
index 866f809..779dde5 100644
--- a/tools/tools-common.h
+++ b/tools/tools-common.h
@@ -1,9 +1,5 @@ 
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
-/*
- * This file is part of libgpiod.
- *
- * Copyright (C) 2017-2018 Bartosz Golaszewski <bartekgola@gmail.com>
- */
+/* SPDX-FileCopyrightText: 2017-2021 Bartosz Golaszewski <bartekgola@gmail.com> */
 
 #ifndef __GPIOD_TOOLS_COMMON_H__
 #define __GPIOD_TOOLS_COMMON_H__