[00/53] Get rid of UTF-8 chars that can be mapped as ASCII

There are several UTF-8 characters at the Kernel's documentation.

Several of them were due to the process of converting files from
DocBook, LaTeX, HTML and Markdown. They were probably introduced
by the conversion tools used on that time.

Other UTF-8 characters were added along the time, but they're easily
replaceable by ASCII chars.

As Linux developers are all around the globe, and not everybody has UTF-8
as their default charset, better to use UTF-8 only on cases where it is really
needed.

The first 3 patches on this series were manually written, in order to solve
a few special cases.

The remaining patches on series address such cases on *.rst files and 
inside the Documentation/ABI, using this perl map table in order to do the
charset conversion:

my %char_map = (
	0x2010 => '-',		# HYPHEN
	0xad   => '-',		# SOFT HYPHEN
	0x2013 => '-',		# EN DASH
	0x2014 => '-',		# EM DASH

	0x2018 => "'",		# LEFT SINGLE QUOTATION MARK
	0x2019 => "'",		# RIGHT SINGLE QUOTATION MARK
	0xb4   => "'",		# ACUTE ACCENT

	0x201c => '"',		# LEFT DOUBLE QUOTATION MARK
	0x201d => '"',		# RIGHT DOUBLE QUOTATION MARK

	0x2212 => '-',		# MINUS SIGN
	0x2217 => '*',		# ASTERISK OPERATOR
	0xd7   => 'x',		# MULTIPLICATION SIGN

	0xbb   => '>',		# RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK

	0xa0   => ' ',		# NO-BREAK SPACE
	0xfeff => '',		# ZERO WIDTH NO-BREAK SPACE
);

After the conversion, those UTF-8 chars will be kept:

	- U+00a9 ('©'): COPYRIGHT SIGN
	- U+00ac ('¬'): NOT SIGN		# only at Documentation/powerpc/transactional_memory.rst
	- U+00ae ('®'): REGISTERED SIGN
	- U+00b0 ('°'): DEGREE SIGN
	- U+00b1 ('±'): PLUS-MINUS SIGN
	- U+00b2 ('²'): SUPERSCRIPT TWO
	- U+00b5 ('µ'): MICRO SIGN
	- U+00b7 ('·'): MIDDLE DOT		# See below
	- U+00bd ('½'): VULGAR FRACTION ONE HALF
	- U+00c7 ('Ç'): LATIN CAPITAL LETTER C WITH CEDILLA
	- U+00df ('ß'): LATIN SMALL LETTER SHARP S
	- U+00e1 ('á'): LATIN SMALL LETTER A WITH ACUTE
	- U+00e4 ('ä'): LATIN SMALL LETTER A WITH DIAERESIS
	- U+00e6 ('æ'): LATIN SMALL LETTER AE
	- U+00e7 ('ç'): LATIN SMALL LETTER C WITH CEDILLA
	- U+00e9 ('é'): LATIN SMALL LETTER E WITH ACUTE
	- U+00ea ('ê'): LATIN SMALL LETTER E WITH CIRCUMFLEX
	- U+00eb ('ë'): LATIN SMALL LETTER E WITH DIAERESIS
	- U+00f3 ('ó'): LATIN SMALL LETTER O WITH ACUTE
	- U+00f4 ('ô'): LATIN SMALL LETTER O WITH CIRCUMFLEX
	- U+00f6 ('ö'): LATIN SMALL LETTER O WITH DIAERESIS
	- U+00f8 ('ø'): LATIN SMALL LETTER O WITH STROKE
	- U+00fa ('ú'): LATIN SMALL LETTER U WITH ACUTE
	- U+00fc ('ü'): LATIN SMALL LETTER U WITH DIAERESIS
	- U+00fd ('ý'): LATIN SMALL LETTER Y WITH ACUTE
	- U+011f ('ğ'): LATIN SMALL LETTER G WITH BREVE
	- U+0142 ('ł'): LATIN SMALL LETTER L WITH STROKE
	- U+03bc ('μ'): GREEK SMALL LETTER MU
	- U+2026 ('…'): HORIZONTAL ELLIPSIS
	- U+2122 ('™'): TRADE MARK SIGN
	- U+2191 ('↑'): UPWARDS ARROW
	- U+2192 ('→'): RIGHTWARDS ARROW
	- U+2193 ('↓'): DOWNWARDS ARROW
	- U+2264 ('≤'): LESS-THAN OR EQUAL TO
	- U+2265 ('≥'): GREATER-THAN OR EQUAL TO
	- U+2500 ('─'): BOX DRAWINGS LIGHT HORIZONTAL
	- U+2502 ('│'): BOX DRAWINGS LIGHT VERTICAL
	- U+2514 ('└'): BOX DRAWINGS LIGHT UP AND RIGHT
	- U+251c ('├'): BOX DRAWINGS LIGHT VERTICAL AND RIGHT
	- U+2b0d ('⬍'): UP DOWN BLACK ARROW

PS.: maintainers were bcc on patch 00/53, in order to reduce the
risk of patch 00 to be rejected by list servers.

-

For U+00b7 ('·'): MIDDLE DOT, I opted to keep it on a few places:

- Documentation/devicetree/bindings/clock/qcom,rpmcc.txt

  As this file will be some day converted to yaml, where the 
  MIDDLE DOT will be removed, I guess it is not worth touching it.

- Documentation/scheduler/sched-deadline.rst

  There, it is used on a math expressions. So, better to keep.

- Documentation/devicetree/bindings/media/video-interface-devices.yaml

  There, it part of an ASCII artwork.

- translations/zh_CN

  I prefer not touching it, as it might have some special meaning in Simplified Chinese.

Mauro Carvalho Chehab (53):
  docs: cdrom-standard.rst: get rid of uneeded UTF-8 chars
  docs: ABI: remove a meaningless UTF-8 character
  docs: ABI: remove some spurious characters
  docs: index.rst: avoid using UTF-8 chars
  docs: hwmon: avoid using UTF-8 chars
  docs: admin-guide: avoid using UTF-8 chars
  docs: admin-guide: media: ipu3.rst: avoid using UTF-8 chars
  docs: admin-guide: sysctl: kernel.rst: avoid using UTF-8 chars
  docs: admin-guide: perf: imx-ddr.rst: avoid using UTF-8 chars
  docs: admin-guide: pm: avoid using UTF-8 chars
  docs: trace: coresight: coresight-etm4x-reference.rst: avoid using
    UTF-8 chars
  docs: driver-api: avoid using UTF-8 chars
  docs: driver-api: fpga: avoid using UTF-8 chars
  docs: driver-api: iio: avoid using UTF-8 chars
  docs: driver-api: thermal: avoid using UTF-8 chars
  docs: driver-api: media: drivers: avoid using UTF-8 chars
  docs: driver-api: firmware: other_interfaces.rst: avoid using UTF-8
    chars
  docs: driver-api: nvdimm: btt.rst: avoid using UTF-8 chars
  docs: fault-injection: nvme-fault-injection.rst: avoid using UTF-8
    chars
  docs: usb: avoid using UTF-8 chars
  docs: process: avoid using UTF-8 chars
  docs: block: data-integrity.rst: avoid using UTF-8 chars
  docs: userspace-api: media: fdl-appendix.rst: avoid using UTF-8 chars
  docs: userspace-api: media: v4l: avoid using UTF-8 chars
  docs: userspace-api: media: dvb: avoid using UTF-8 chars
  docs: vm: zswap.rst: avoid using UTF-8 chars
  docs: filesystems: f2fs.rst: avoid using UTF-8 chars
  docs: filesystems: ext4: avoid using UTF-8 chars
  docs: kernel-hacking: avoid using UTF-8 chars
  docs: hid: avoid using UTF-8 chars
  docs: security: tpm: avoid using UTF-8 chars
  docs: security: keys: trusted-encrypted.rst: avoid using UTF-8 chars
  docs: riscv: vm-layout.rst: avoid using UTF-8 chars
  docs: networking: scaling.rst: avoid using UTF-8 chars
  docs: networking: devlink: devlink-dpipe.rst: avoid using UTF-8 chars
  docs: networking: device_drivers: avoid using UTF-8 chars
  docs: x86: avoid using UTF-8 chars
  docs: scheduler: sched-deadline.rst: avoid using UTF-8 chars
  docs: dev-tools: testing-overview.rst: avoid using UTF-8 chars
  docs: power: powercap: powercap.rst: avoid using UTF-8 chars
  docs: ABI: avoid using UTF-8 chars
  docs: doc-guide: contributing.rst: avoid using UTF-8 chars
  docs: PCI: acpi-info.rst: avoid using UTF-8 chars
  docs: gpu: avoid using UTF-8 chars
  docs: sound: kernel-api: writing-an-alsa-driver.rst: avoid using UTF-8
    chars
  docs: arm64: arm-acpi.rst: avoid using UTF-8 chars
  docs: infiniband: tag_matching.rst: avoid using UTF-8 chars
  docs: timers: no_hz.rst: avoid using UTF-8 chars
  docs: misc-devices: ibmvmc.rst: avoid using UTF-8 chars
  docs: firmware-guide: acpi: lpit.rst: avoid using UTF-8 chars
  docs: firmware-guide: acpi: dsd: graph.rst: avoid using UTF-8 chars
  docs: virt: kvm: avoid using UTF-8 chars
  docs: RCU: avoid using UTF-8 chars

 .../obsolete/sysfs-kernel-fadump_registered   |   2 +-
 .../obsolete/sysfs-kernel-fadump_release_mem  |   2 +-
 ...sfs-class-chromeos-driver-cros-ec-lightbar |   2 +-
 .../ABI/testing/sysfs-class-net-cdc_ncm       |   2 +-
 .../ABI/testing/sysfs-devices-platform-ipmi   |   2 +-
 .../testing/sysfs-devices-platform-trackpoint |   2 +-
 Documentation/ABI/testing/sysfs-devices-soc   |   4 +-
 Documentation/ABI/testing/sysfs-module        |   4 +-
 Documentation/PCI/acpi-info.rst               |  26 +-
 .../Data-Structures/Data-Structures.rst       |  52 ++--
 .../Expedited-Grace-Periods.rst               |  40 +--
 .../Tree-RCU-Memory-Ordering.rst              |  10 +-
 .../RCU/Design/Requirements/Requirements.rst  | 126 ++++-----
 Documentation/admin-guide/index.rst           |   2 +-
 Documentation/admin-guide/media/ipu3.rst      |   2 +-
 Documentation/admin-guide/module-signing.rst  |   4 +-
 Documentation/admin-guide/perf/imx-ddr.rst    |   2 +-
 Documentation/admin-guide/pm/intel_idle.rst   |   4 +-
 Documentation/admin-guide/pm/intel_pstate.rst |   4 +-
 Documentation/admin-guide/ras.rst             |  94 +++----
 .../admin-guide/reporting-issues.rst          |  12 +-
 Documentation/admin-guide/sysctl/kernel.rst   |   2 +-
 Documentation/arm64/arm-acpi.rst              |   8 +-
 Documentation/block/data-integrity.rst        |   2 +-
 Documentation/cdrom/cdrom-standard.rst        |  30 +--
 Documentation/dev-tools/testing-overview.rst  |   4 +-
 Documentation/doc-guide/contributing.rst      |   2 +-
 .../driver-api/firmware/other_interfaces.rst  |   2 +-
 Documentation/driver-api/fpga/fpga-bridge.rst |  10 +-
 Documentation/driver-api/fpga/fpga-mgr.rst    |  12 +-
 .../driver-api/fpga/fpga-programming.rst      |   8 +-
 Documentation/driver-api/fpga/fpga-region.rst |  20 +-
 Documentation/driver-api/iio/buffers.rst      |   8 +-
 Documentation/driver-api/iio/hw-consumer.rst  |  10 +-
 .../driver-api/iio/triggered-buffers.rst      |   6 +-
 Documentation/driver-api/iio/triggers.rst     |  10 +-
 Documentation/driver-api/index.rst            |   2 +-
 Documentation/driver-api/ioctl.rst            |   8 +-
 .../media/drivers/sh_mobile_ceu_camera.rst    |   8 +-
 .../driver-api/media/drivers/vidtv.rst        |   4 +-
 .../driver-api/media/drivers/zoran.rst        |   2 +-
 Documentation/driver-api/nvdimm/btt.rst       |   2 +-
 .../driver-api/thermal/cpu-idle-cooling.rst   |  14 +-
 .../driver-api/thermal/intel_powerclamp.rst   |   6 +-
 .../thermal/x86_pkg_temperature_thermal.rst   |   2 +-
 .../fault-injection/nvme-fault-injection.rst  |   2 +-
 Documentation/filesystems/ext4/attributes.rst |  20 +-
 Documentation/filesystems/ext4/bigalloc.rst   |   6 +-
 Documentation/filesystems/ext4/blockgroup.rst |   8 +-
 Documentation/filesystems/ext4/blocks.rst     |   2 +-
 Documentation/filesystems/ext4/directory.rst  |  16 +-
 Documentation/filesystems/ext4/eainode.rst    |   2 +-
 Documentation/filesystems/ext4/inlinedata.rst |   6 +-
 Documentation/filesystems/ext4/inodes.rst     |   6 +-
 Documentation/filesystems/ext4/journal.rst    |   8 +-
 Documentation/filesystems/ext4/mmp.rst        |   2 +-
 .../filesystems/ext4/special_inodes.rst       |   4 +-
 Documentation/filesystems/ext4/super.rst      |  10 +-
 Documentation/filesystems/f2fs.rst            |   6 +-
 .../firmware-guide/acpi/dsd/graph.rst         |   2 +-
 Documentation/firmware-guide/acpi/lpit.rst    |   2 +-
 Documentation/gpu/i915.rst                    |   2 +-
 Documentation/gpu/komeda-kms.rst              |   2 +-
 Documentation/hid/hid-sensor.rst              |  70 ++---
 Documentation/hid/intel-ish-hid.rst           | 246 +++++++++---------
 Documentation/hwmon/ir36021.rst               |   2 +-
 Documentation/hwmon/ltc2992.rst               |   2 +-
 Documentation/hwmon/pm6764tr.rst              |   2 +-
 Documentation/hwmon/tmp103.rst                |   4 +-
 Documentation/index.rst                       |   4 +-
 Documentation/infiniband/tag_matching.rst     |   8 +-
 Documentation/kernel-hacking/hacking.rst      |   2 +-
 Documentation/kernel-hacking/locking.rst      |   2 +-
 Documentation/misc-devices/ibmvmc.rst         |   8 +-
 .../device_drivers/ethernet/intel/i40e.rst    |  12 +-
 .../device_drivers/ethernet/intel/iavf.rst    |   6 +-
 .../device_drivers/ethernet/netronome/nfp.rst |  12 +-
 .../networking/devlink/devlink-dpipe.rst      |   2 +-
 Documentation/networking/scaling.rst          |  18 +-
 Documentation/power/powercap/powercap.rst     | 210 +++++++--------
 Documentation/process/code-of-conduct.rst     |   2 +-
 .../process/kernel-enforcement-statement.rst  |   2 +-
 Documentation/riscv/vm-layout.rst             |   2 +-
 Documentation/scheduler/sched-deadline.rst    |   4 +-
 .../security/keys/trusted-encrypted.rst       |   4 +-
 Documentation/security/tpm/tpm_event_log.rst  |   2 +-
 Documentation/security/tpm/xen-tpmfront.rst   |   2 +-
 .../kernel-api/writing-an-alsa-driver.rst     |  68 ++---
 Documentation/timers/no_hz.rst                |   2 +-
 .../coresight/coresight-etm4x-reference.rst   |  16 +-
 Documentation/usb/ehci.rst                    |   2 +-
 Documentation/usb/gadget_printer.rst          |   2 +-
 Documentation/usb/mass-storage.rst            |  36 +--
 Documentation/usb/mtouchusb.rst               |   2 +-
 Documentation/usb/usb-serial.rst              |   2 +-
 .../media/dvb/audio-set-bypass-mode.rst       |   2 +-
 .../userspace-api/media/dvb/audio.rst         |   2 +-
 .../userspace-api/media/dvb/dmx-fopen.rst     |   2 +-
 .../userspace-api/media/dvb/dmx-fread.rst     |   2 +-
 .../media/dvb/dmx-set-filter.rst              |   2 +-
 .../userspace-api/media/dvb/intro.rst         |   6 +-
 .../userspace-api/media/dvb/video.rst         |   2 +-
 .../userspace-api/media/fdl-appendix.rst      |  64 ++---
 .../userspace-api/media/v4l/biblio.rst        |   8 +-
 .../userspace-api/media/v4l/crop.rst          |  16 +-
 .../userspace-api/media/v4l/dev-decoder.rst   |   6 +-
 .../userspace-api/media/v4l/diff-v4l.rst      |   2 +-
 .../userspace-api/media/v4l/open.rst          |   2 +-
 .../media/v4l/vidioc-cropcap.rst              |   4 +-
 Documentation/virt/kvm/api.rst                |  28 +-
 .../virt/kvm/running-nested-guests.rst        |  12 +-
 Documentation/vm/zswap.rst                    |   4 +-
 Documentation/x86/resctrl.rst                 |   2 +-
 Documentation/x86/sgx.rst                     |   4 +-
 114 files changed, 807 insertions(+), 807 deletions(-)

On Mon, 2021-05-10 at 12:26 +0200, Mauro Carvalho Chehab wrote:
> There are several UTF-8 characters at the Kernel's documentation.
> 
> Several of them were due to the process of converting files from
> DocBook, LaTeX, HTML and Markdown. They were probably introduced
> by the conversion tools used on that time.
> 
> Other UTF-8 characters were added along the time, but they're easily
> replaceable by ASCII chars.
> 
> As Linux developers are all around the globe, and not everybody has UTF-8
> as their default charset, better to use UTF-8 only on cases where it is really
> needed.

No, that is absolutely the wrong approach.

If someone has a local setup which makes bogus assumptions about text
encodings, that is their own mistake.

We don't do them any favours by trying to *hide* it in the common case
so that they don't notice it for longer.

There really isn't much excuse for such brokenness, this far into the
21st century.

Even *before* UTF-8 came along in the final decade of the last
millennium, it was important to know which character set a given piece
of text was encoded in.

In fact it was even *more* important back then, we couldn't just assume
UTF-8 everywhere like we can in modern times.

Git can already do things like CRLF conversion on checking files out to
match local conventions; if you want to teach it to do character set
conversions too then I suppose that might be useful to a few developers
who've fallen through a time warp and still need it. But nobody's ever
bothered before because it just isn't necessary these days.

Please *don't* attempt to address this anachronistic and esoteric
"requirement" by dragging the kernel source back in time by three
decades.

Em Mon, 10 May 2021 12:52:44 +0200
Thorsten Leemhuis <linux@leemhuis.info> escreveu:

> On 10.05.21 12:26, Mauro Carvalho Chehab wrote:
> >
> > As Linux developers are all around the globe, and not everybody has UTF-8
> > as their default charset, better to use UTF-8 only on cases where it is really
> > needed.
> > […]
> > The remaining patches on series address such cases on *.rst files and 
> > inside the Documentation/ABI, using this perl map table in order to do the
> > charset conversion:
> > 
> > my %char_map = (
> > […]
> > 	0x2013 => '-',		# EN DASH
> > 	0x2014 => '-',		# EM DASH  


> I might be performing bike shedding here, but wouldn't it be better to
> replace those two with "--", as explained in
> https://en.wikipedia.org/wiki/Dash#Approximating_the_em_dash_with_two_or_three_hyphens
> 
> For EM DASH there seems to be even "---", but I'd say that is a bit too
> much.

Yeah, we can do, instead:

 	0x2013 => '--',		# EN DASH
 	0x2014 => '---',	# EM DASH  

I was actually in doubt about those ;-)

Btw, when producing HTML documentation,  Sphinx should convert:
	-- into EN DASH
and:
	--- into EM DASH

So, the resulting html will be identical.

> Or do you fear the extra work as some lines then might break the
> 80-character limit then?

No, I suspect that the line size won't be an issue. Some care should
taken when EN DASH and EM DASH are used inside tables.

Thanks,
Mauro

Hi David,

Em Mon, 10 May 2021 11:54:02 +0100
David Woodhouse <dwmw2@infradead.org> escreveu:

> On Mon, 2021-05-10 at 12:26 +0200, Mauro Carvalho Chehab wrote:
> > There are several UTF-8 characters at the Kernel's documentation.
> > 
> > Several of them were due to the process of converting files from
> > DocBook, LaTeX, HTML and Markdown. They were probably introduced
> > by the conversion tools used on that time.
> > 
> > Other UTF-8 characters were added along the time, but they're easily
> > replaceable by ASCII chars.
> > 
> > As Linux developers are all around the globe, and not everybody has UTF-8
> > as their default charset, better to use UTF-8 only on cases where it is really
> > needed.  
> 
> No, that is absolutely the wrong approach.
> 
> If someone has a local setup which makes bogus assumptions about text
> encodings, that is their own mistake.
> 
> We don't do them any favours by trying to *hide* it in the common case
> so that they don't notice it for longer.
> 
> There really isn't much excuse for such brokenness, this far into the
> 21st century.
> 
> Even *before* UTF-8 came along in the final decade of the last
> millennium, it was important to know which character set a given piece
> of text was encoded in.
> 
> In fact it was even *more* important back then, we couldn't just assume
> UTF-8 everywhere like we can in modern times.
> 
> Git can already do things like CRLF conversion on checking files out to
> match local conventions; if you want to teach it to do character set
> conversions too then I suppose that might be useful to a few developers
> who've fallen through a time warp and still need it. But nobody's ever
> bothered before because it just isn't necessary these days.
> 
> Please *don't* attempt to address this anachronistic and esoteric
> "requirement" by dragging the kernel source back in time by three
> decades.

No. The idea is not to go back three decades ago. 

The goal is just to avoid use UTF-8 where it is not needed. See, the vast
majority of UTF-8 chars are kept:

	- Non-ASCII Latin and Greek chars;
	- Box drawings;
	- arrows;
	- most symbols.

There, it makes perfect sense to keep using UTF-8.

We should keep using UTF-8 on Kernel. This is something that it shouldn't
be changed.

---

This patch series is doing conversion only when using ASCII makes
more sense than using UTF-8. 

See, a number of converted documents ended with weird characters
like ZERO WIDTH NO-BREAK SPACE (U+FEFF) character. This specific
character doesn't do any good.

Others use NO-BREAK SPACE (U+A0) instead of 0x20. Harmless, until
someone tries to use grep[1].

[1] try to run:

    $ git grep "CPU 0 has been" Documentation/RCU/

    it will return nothing with current upstream.

    But it will work fine after the series is applied:

    $ git grep "CPU 0 has been" Documentation/RCU/
      Documentation/RCU/Design/Data-Structures/Data-Structures.rst:| #. CPU 0 has been in dyntick-idle mode for quite some time. When it   |
      Documentation/RCU/Design/Data-Structures/Data-Structures.rst:|    notices that CPU 0 has been in dyntick idle mode, which qualifies  |

The main point on this series is to replace just the occurrences
where ASCII represents the symbol equally well, e. g. it is limited
for those chars:

	- U+2010 ('‐'): HYPHEN
	- U+00ad ('­'): SOFT HYPHEN
	- U+2013 ('–'): EN DASH
	- U+2014 ('—'): EM DASH

	- U+2018 ('‘'): LEFT SINGLE QUOTATION MARK
	- U+2019 ('’'): RIGHT SINGLE QUOTATION MARK
	- U+00b4 ('´'): ACUTE ACCENT

	- U+201c ('“'): LEFT DOUBLE QUOTATION MARK
	- U+201d ('”'): RIGHT DOUBLE QUOTATION MARK

	- U+00d7 ('×'): MULTIPLICATION SIGN
	- U+2212 ('−'): MINUS SIGN

	- U+2217 ('∗'): ASTERISK OPERATOR
	  (this one used as a pointer reference like "*foo" on C code
	   example inside a document converted from LaTeX)

	- U+00bb ('»'): RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
	  (this one also used wrongly on an ABI file, meaning '>')

	- U+00a0 (' '): NO-BREAK SPACE
	- U+feff (''): ZERO WIDTH NO-BREAK SPACE

Using the above symbols will just trick tools like grep for no good
reason.

Thanks,
Mauro

Em Mon, 10 May 2021 14:16:16 +0100
Edward Cree <ecree.xilinx@gmail.com> escreveu:

> On 10/05/2021 12:55, Mauro Carvalho Chehab wrote:
> > The main point on this series is to replace just the occurrences
> > where ASCII represents the symbol equally well  
> 
> > 	- U+2014 ('—'): EM DASH  
> Em dash is not the same thing as hyphen-minus, and the latter does not
>  serve 'equally well'.  People use em dashes because — even in
>  monospace fonts — they make text easier to read and comprehend, when
>  used correctly.

True, but if you look at the diff, on several places, IMHO a single
hyphen would make more sensus. Maybe those places came from a converted
doc.

> I accept that some of the other distinctions — like en dashes — are
>  needlessly pedantic (though I don't doubt there is someone out there
>  who will gladly defend them with the same fervour with which I argue
>  for the em dash) and I wouldn't take the trouble to use them myself;
>  but I think there is a reasonable assumption that when someone goes
>  to the effort of using a Unicode punctuation mark that is semantic
>  (rather than merely typographical), they probably had a reason for
>  doing so.
> 
> > 	- U+2018 ('‘'): LEFT SINGLE QUOTATION MARK
> > 	- U+2019 ('’'): RIGHT SINGLE QUOTATION MARK
> > 	- U+201c ('“'): LEFT DOUBLE QUOTATION MARK
> > 	- U+201d ('”'): RIGHT DOUBLE QUOTATION MARK  
> (These are purely typographic, I have no problem with dumping them.)
> 
> > 	- U+00d7 ('×'): MULTIPLICATION SIGN  
> Presumably this is appearing in mathematical formulae, in which case
>  changing it to 'x' loses semantic information.
> 
> > Using the above symbols will just trick tools like grep for no good
> > reason.  
> NBSP, sure.  That one's probably an artefact of some document format
>  conversion somewhere along the line, anyway.
> But what kinds of things with × or — in are going to be grept for?

Actually, on almost all places, those aren't used inside math formulae, but
instead, they describe video some resolutions:

	$ git grep × Documentation/
	Documentation/devicetree/bindings/display/panel/asus,z00t-tm5p5-nt35596.yaml:title: ASUS Z00T TM5P5 NT35596 5.5" 1080×1920 LCD Panel
	Documentation/devicetree/bindings/display/panel/panel-simple-dsi.yaml:        # LG ACX467AKM-7 4.95" 1080×1920 LCD Panel
	Documentation/devicetree/bindings/sound/tlv320adcx140.yaml:      1 - Mic bias is set to VREF × 1.096
	Documentation/userspace-api/media/v4l/crop.rst:of 16 × 16 pixels. The source cropping rectangle is set to defaults,
	Documentation/userspace-api/media/v4l/crop.rst:which are also the upper limit in this example, of 640 × 400 pixels at
	Documentation/userspace-api/media/v4l/crop.rst:offset 0, 0. An application requests an image size of 300 × 225 pixels,
	Documentation/userspace-api/media/v4l/crop.rst:The driver sets the image size to the closest possible values 304 × 224,
	Documentation/userspace-api/media/v4l/crop.rst:is 608 × 224 (224 × 2:1 would exceed the limit 400). The offset 0, 0 is
	Documentation/userspace-api/media/v4l/crop.rst:rectangle of 608 × 456 pixels. The present scaling factors limit
	Documentation/userspace-api/media/v4l/crop.rst:cropping to 640 × 384, so the driver returns the cropping size 608 × 384
	Documentation/userspace-api/media/v4l/crop.rst:and adjusts the image size to closest possible 304 × 192.
	Documentation/userspace-api/media/v4l/diff-v4l.rst:size bitmap of 1024 × 625 bits. Struct :c:type:`v4l2_window`
	Documentation/userspace-api/media/v4l/vidioc-cropcap.rst:       Assuming pixel aspect 1/1 this could be for example a 640 × 480
	Documentation/userspace-api/media/v4l/vidioc-cropcap.rst:       rectangle for NTSC, a 768 × 576 rectangle for PAL and SECAM

it is a way more likely that, if someone wants to grep, they would be 
doing something like this, in order to get video resolutions:

	$ git grep -E "\b[1-9][0-9]+\s*x\s*[0-9]+\b" Documentation/
	Documentation/ABI/obsolete/sysfs-driver-hid-roccat-koneplus:Description:        When read the mouse returns a 30x30 pixel image of the
	Documentation/ABI/obsolete/sysfs-driver-hid-roccat-konepure:Description:        When read the mouse returns a 30x30 pixel image of the
	Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7:               Provides access to the binary "24x7 catalog" provided by the
	Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7:               https://raw.githubusercontent.com/jmesmon/catalog-24x7/master/hv-24x7-	catalog.h
	Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7:               Exposes the "version" field of the 24x7 catalog. This is also
	Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7:               HCALLs to retrieve hv-24x7 pmu event counter data.
	Documentation/ABI/testing/sysfs-bus-vfio-mdev:          "2 heads, 512M FB, 2560x1600 maximum resolution"
	Documentation/ABI/testing/sysfs-driver-wacom:           of the device. The image is a 64x32 pixel 4-bit gray image. The
	Documentation/ABI/testing/sysfs-driver-wacom:           1024 byte binary is split up into 16x 64 byte chunks. Each 64
	Documentation/ABI/testing/sysfs-driver-wacom:           image has to contain 256 bytes (64x32 px 1 bit colour).
	Documentation/admin-guide/edid.rst:commonly used screen resolutions (800x600, 1024x768, 1280x1024, 1600x1200,
	Documentation/admin-guide/edid.rst:1680x1050, 1920x1080) as binary blobs, but the kernel source tree does
	Documentation/admin-guide/edid.rst:If you want to create your own EDID file, copy the file 1024x768.S,
	Documentation/admin-guide/kernel-parameters.txt:                        edid/1024x768.bin, edid/1280x1024.bin,
	Documentation/admin-guide/kernel-parameters.txt:                        edid/1680x1050.bin, or edid/1920x1080.bin is given
	Documentation/admin-guide/kernel-parameters.txt:                        2 - The VGA Shield is attached (1024x768)
	Documentation/admin-guide/media/dvb_intro.rst:signal encoded at a resolution of 768x576 24-bit color pixels over 25
	Documentation/admin-guide/media/imx.rst:1280x960 input frame to 640x480, and then /2 downscale in both
	Documentation/admin-guide/media/imx.rst:dimensions to 320x240 (assumes ipu1_csi0 is linked to ipu1_csi0_mux):
	Documentation/admin-guide/media/imx.rst:   media-ctl -V "'ipu1_csi0_mux':2[fmt:UYVY2X8/1280x960]"

which won't get the above, due to the usage of the UTF-8 alternative.

In any case, replacing all the above by 'x' seems to be the right thing,
at least on my eyes.

> If there are em dashes lying around that semantically _should_ be
>  hyphen-minus (one of your patches I've seen, for instance, fixes an
>  *en* dash moonlighting as the option character in an `ethtool`
>  command line), then sure, convert them.
> But any time someone is using a Unicode character to *express
>  semantics*, even if you happen to think the semantic distinction
>  involved is a pedantic or unimportant one, I think you need an
>  explicit grep case to justify ASCIIfying it.

Yeah, in the case of hyphen/dash it seems to make sense to double check
it.

Thanks,
Mauro

On Mon, 2021-05-10 at 13:55 +0200, Mauro Carvalho Chehab wrote:
> This patch series is doing conversion only when using ASCII makes
> more sense than using UTF-8. 
> 
> See, a number of converted documents ended with weird characters
> like ZERO WIDTH NO-BREAK SPACE (U+FEFF) character. This specific
> character doesn't do any good.
> 
> Others use NO-BREAK SPACE (U+A0) instead of 0x20. Harmless, until
> someone tries to use grep[1].

Replacing those makes sense. But replacing emdashes — which are a
distinct character that has no direct replacement in ASCII and which
people do *deliberately* use instead of hyphen-minus — does not.

Perhaps stick to those two, and any cases where an emdash or endash has
been used where U+002D HYPHEN-MINUS *should* have been used.

And please fix your cover letter which made no reference to 'grep', and
only presented a completely bogus argument for the change instead.

On 10/05/2021 14:38, Mauro Carvalho Chehab wrote:
> Em Mon, 10 May 2021 14:16:16 +0100
> Edward Cree <ecree.xilinx@gmail.com> escreveu:
>> But what kinds of things with × or — in are going to be grept for?
> 
> Actually, on almost all places, those aren't used inside math formulae, but
> instead, they describe video some resolutions:
Ehh, those are also proper uses of ×.  It's still a multiplication,
 after all.

> it is a way more likely that, if someone wants to grep, they would be 
> doing something like this, in order to get video resolutions:
Why would someone be grepping for "all video resolutions mentioned in
 the documentation"?  That seems contrived to me.

-ed

On 10/05/2021 14:59, Matthew Wilcox wrote:
> Most of these
> UTF-8 characters come from latex conversions and really aren't
> necessary (and are being used incorrectly).
I fully agree with fixing those.
The cover-letter, however, gave the impression that that was not the
 main purpose of this series; just, perhaps, a happy side-effect.

> You seem quite knowedgeable about the various differences.  Perhaps
> you'd be willing to write a document for Documentation/doc-guide/
> that provides guidance for when to use which kinds of horizontal
> line?I have Opinions about the proper usage of punctuation, but I also know
 that other people have differing opinions.  For instance, I place
 spaces around an em dash, which is nonstandard according to most
 style guides.  Really this is an individual enough thing that I'm not
 sure we could have a "kernel style guide" that would be more useful
 than general-purpose guidance like the page you linked.
Moreover, such a guide could make non-native speakers needlessly self-
 conscious about their writing and discourage them from contributing
 documentation at all.  I'm not advocating here for trying to push
 kernel developers towards an eats-shoots-and-leaves level of
 linguistic pedantry; rather, I merely think that existing correct
 usages should be left intact (and therefore, excising incorrect usage
 should only be attempted by someone with both the expertise and time
 to check each case).

But if you really want such a doc I wouldn't mind contributing to it.

-ed

On Mon, May 10, 2021 at 12:26:12PM +0200, Mauro Carvalho Chehab wrote:
> There are several UTF-8 characters at the Kernel's documentation.
[...]
> Other UTF-8 characters were added along the time, but they're easily
> replaceable by ASCII chars.
> 
> As Linux developers are all around the globe, and not everybody has UTF-8
> as their default charset

I'm not aware of a distribution that still allows selecting a non-UTF-8
charset in a normal flow in their installer.  And if they haven't purged
support for ancient encodings, that support is thoroughly bitrotten.
Thus, I disagree that this is a legitimate concern.

What _could_ be a legitimate reason is that someone is on a _terminal_
that can't display a wide enough set of glyphs.  Such terminals are:
 • Linux console (because of vgacon limitations; patchsets to improve
   other cons haven't been mainlined)
 • some Windows terminals (putty, old Windows console) that can't borrow
   glyphs from other fonts like fontconfig can

For the former, it's whatever your distribution ships in
/usr/share/consolefonts/ or an equivalent, which is based on historic
ISO-8859 and VT100 traditions.

For the latter, the near-guaranteed character set is WGL4.


Thus, at least two of your choices seem to disagree with the above:
[dropped]
> 	0xd7   => 'x',		# MULTIPLICATION SIGN
[retained]
> 	- U+2b0d ('⬍'): UP DOWN BLACK ARROW

× is present in ISO-8859, V100, WGL4; I've found no font in
/usr/share/consolefonts/ on my Debian unstable box that lacks this
character.

⬍ is not found in any of the above.  You might want to at least
convert it to ↕ which is at least present in WGL4, and thus likely
to be supported in fonts heeding Windows/Mac/OpenType recommendations.
That still won't make it work on VT.


Meow!

Em Mon, 10 May 2021 15:33:47 +0100
Edward Cree <ecree.xilinx@gmail.com> escreveu:

> On 10/05/2021 14:59, Matthew Wilcox wrote:
> > Most of these
> > UTF-8 characters come from latex conversions and really aren't
> > necessary (and are being used incorrectly).  
> I fully agree with fixing those.
> The cover-letter, however, gave the impression that that was not the
>  main purpose of this series; just, perhaps, a happy side-effect.

Sorry for the mess. The main reason why I wrote this series is because
there are lots of UTF-8 left-over chars from the ReST conversion.
See:
  - https://lore.kernel.org/linux-doc/20210507100435.3095f924@coco.lan/

A large set of the UTF-8 letf-over chars were due to my conversion work,
so I feel personally responsible to fix those ;-)

Yet, this series has two positive side effects:

 - it helps people needing to touch the documents using non-utf8 locales[1];
 - it makes easier to grep for a text;

[1] There are still some widely used distros nowadays (LTS ones?) that
    don't set UTF-8 as default. Last time I installed a Debian machine
    I had to explicitly set UTF-8 charset after install as the default
    were using ASCII encoding (can't remember if it was Debian 10 or an
    older version).

Unintentionally, I ended by giving emphasis to the non-utf8 instead of
giving emphasis to the conversion left-overs.

FYI, this patch series originated from a discussion at linux-doc,
reporting that Sphinx breaks when LANG is not set to utf-8[2]. That's
why I probably ended giving the wrong emphasis at the cover letter.

[2] See https://lore.kernel.org/linux-doc/20210506103913.GE6564@kitsune.suse.cz/
    for the original report. I strongly suspect that the VM set by Michal 
    to build the docs was using a distro that doesn't set UTF-8 as default.

    PS.: 
      I intend to prepare afterwards a separate fix to avoid Sphinx
      logger to crash during Kernel doc builds when the locale charset
      is not UTF-8, but I'm not too fluent in python. So, I need some
      time to check if are there a way to just avoid python log crashes
      without touching Sphinx code and without needing to trick it to 
      think that the machine's locale is UTF-8.

See: while there was just a single document originally stored at the
Kernel tree as a LaTeX document during the time we did the conversion
(cdrom-standard.tex), there are several other documents stored as 
text that seemed to be generated by some tool like LaTeX, whose the
original version were not preserved. 

Also, there were other documents using different markdown dialects 
that were converted via pandoc (and/or other similar tools). That's 
not to mention the ones that were converted from DocBook. Such
tools tend to use some logic to use "neat" versions of some ASCII
characters, like what this tool does:

	https://daringfireball.net/projects/smartypants/

(Sphinx itself seemed to use this tool on its early versions)

All tool-converted documents can carry UTF-8 on unexpected places. See,
on this series, a large amount of patches deal with U+A0 (NO-BREAK SPACE)
chars. I can't see why someone writing a plain text document (or a ReST
one) would type a NO-BREAK SPACE instead of a normal white space.

The same applies, up to some sort, to curly commas: usually people just 
write ASCII "commas" on their documents, and use some tool like LaTeX
or a text editor like libreoffice in order to convert them into
 “utf-8 curly commas”[3].

[3] Sphinx will do such things at the produced output, doing something 
    similar to what smartypants does, nowadays using this:

	https://docutils.sourceforge.io/docs/user/smartquotes.html

    E. g.:
      - Straight quotes (" and ') turned into "curly" quote characters;
      - dashes (-- and ---) turned into en- and em-dash entities;
      - three consecutive dots (... or . . .) turned into an ellipsis char.

> > You seem quite knowedgeable about the various differences.  Perhaps
> > you'd be willing to write a document for Documentation/doc-guide/
> > that provides guidance for when to use which kinds of horizontal
> > line?
> I have Opinions about the proper usage of punctuation, but I also know  
>  that other people have differing opinions.  For instance, I place
>  spaces around an em dash, which is nonstandard according to most
>  style guides.  Really this is an individual enough thing that I'm not
>  sure we could have a "kernel style guide" that would be more useful
>  than general-purpose guidance like the page you linked.

> Moreover, such a guide could make non-native speakers needlessly self-
>  conscious about their writing and discourage them from contributing
>  documentation at all.

I don't think so. In a matter of fact, as a non-native speaker, I guess
this can actually help people willing to write documents.

>  I'm not advocating here for trying to push
>  kernel developers towards an eats-shoots-and-leaves level of
>  linguistic pedantry; rather, I merely think that existing correct
>  usages should be left intact (and therefore, excising incorrect usage
>  should only be attempted by someone with both the expertise and time
>  to check each case).
> 
> But if you really want such a doc I wouldn't mind contributing to it.

IMO, a document like that can be helpful. I can help reviewing it.

Thanks,
Mauro

On Tue, 2021-05-11 at 11:00 +0200, Mauro Carvalho Chehab wrote:
> Yet, this series has two positive side effects:
> 
>  - it helps people needing to touch the documents using non-utf8 locales[1];
>  - it makes easier to grep for a text;
> 
> [1] There are still some widely used distros nowadays (LTS ones?) that
>     don't set UTF-8 as default. Last time I installed a Debian machine
>     I had to explicitly set UTF-8 charset after install as the default
>     were using ASCII encoding (can't remember if it was Debian 10 or an
>     older version).

This whole line of thinking is fundamentally wrong.

A given set of characters in a "text file" are encoded with a specific
character set / encoding. To interpret that file and convert the bytes
back to characters, we need to use the *same* charset.

That charset is a property of the text file, and each text file or
piece of text in a system (like this email, which will contain a
Content-Type: header indicating the charset) might be encoded with a
*different* character set.

In the days before you could connect computers together — or before you
could exchange data between computers in different countries, at least
— perhaps it made sense to store 'text' files without explicitly noting
their encoding. And to interpret them using some kind of "default"
character set.

Those days are long gone. You're trying to work around an egregiously
stupid bug, if you're trying to pander to "default" encodings. There
*is* no default encoding that even makes sense, except perhaps UTF-8.
To *speak* of them as you did shows a misunderstanding of how broken
they are. It's *precisely* that kind of half-baked thinking which
always used to lead to stupid assumptions and double conversions and
Mojibake. Before we just standardised on UTF-8 everywhere and it
stopped mattering so much.

Just don't.

Now, you *can* make this work if you really insist on it, even for
systems with EBCDIC as their default encoding. Just make git do the
"convert to local charset" on checkout, precisely the same way as it
does CRLF for Windows systems. But it's stupid and anachronistic, so I
don't really see the point.

Em Mon, 10 May 2021 14:49:44 +0100
David Woodhouse <dwmw2@infradead.org> escreveu:

> On Mon, 2021-05-10 at 13:55 +0200, Mauro Carvalho Chehab wrote:
> > This patch series is doing conversion only when using ASCII makes
> > more sense than using UTF-8. 
> > 
> > See, a number of converted documents ended with weird characters
> > like ZERO WIDTH NO-BREAK SPACE (U+FEFF) character. This specific
> > character doesn't do any good.
> > 
> > Others use NO-BREAK SPACE (U+A0) instead of 0x20. Harmless, until
> > someone tries to use grep[1].  
> 
> Replacing those makes sense. But replacing emdashes — which are a
> distinct character that has no direct replacement in ASCII and which
> people do *deliberately* use instead of hyphen-minus — does not.
> 
> Perhaps stick to those two, and any cases where an emdash or endash has
> been used where U+002D HYPHEN-MINUS *should* have been used.

Ok. I'll rework the series excluding EM/EN DASH chars from it.
I'll then apply manually the changes for EM/EN DASH chars 
(probably on a separate series) where it seems to fit. That should
make easier to discuss such replacements.

> And please fix your cover letter which made no reference to 'grep', and
> only presented a completely bogus argument for the change instead.

OK!

Regards,
Mauro

Em Mon, 10 May 2021 15:22:02 -0400
"Theodore Ts'o" <tytso@mit.edu> escreveu:

> On Mon, May 10, 2021 at 02:49:44PM +0100, David Woodhouse wrote:
> > On Mon, 2021-05-10 at 13:55 +0200, Mauro Carvalho Chehab wrote:  
> > > This patch series is doing conversion only when using ASCII makes
> > > more sense than using UTF-8. 
> > > 
> > > See, a number of converted documents ended with weird characters
> > > like ZERO WIDTH NO-BREAK SPACE (U+FEFF) character. This specific
> > > character doesn't do any good.
> > > 
> > > Others use NO-BREAK SPACE (U+A0) instead of 0x20. Harmless, until
> > > someone tries to use grep[1].  
> > 
> > Replacing those makes sense. But replacing emdashes — which are a
> > distinct character that has no direct replacement in ASCII and which
> > people do *deliberately* use instead of hyphen-minus — does not.  
> 
> I regularly use --- for em-dashes and -- for en-dashes.  Markdown will
> automatically translate 3 ASCII hypens to em-dashes, and 2 ASCII
> hyphens to en-dashes.  It's much, much easier for me to type 2 or 3
> hypens into my text editor of choice than trying to enter the UTF-8
> characters. 

Yeah, typing those UTF-8 chars are a lot harder than typing -- and ---
on several text editors ;-)

Here, I only type UTF-8 chars for accents (my US-layout keyboards are 
all set to US international, so typing those are easy).

> If we can make sphinx do this translation, maybe that's
> the best way of dealing with these two characters?

Sphinx already does that by default[1], using smartquotes:

	https://docutils.sourceforge.io/docs/user/smartquotes.html

Those are the conversions that are done there:

      - Straight quotes (" and ') turned into "curly" quote characters;
      - dashes (-- and ---) turned into en- and em-dash entities;
      - three consecutive dots (... or . . .) turned into an ellipsis char.

So, we can simply use single/double commas, hyphens and dots for
curly commas and ellipses.

[1] There's a way to disable it at conf.py, but at the Kernel this is
    kept on its default: to automatically do such conversions. 

Thanks,
Mauro