diff mbox series

[v8,3/6] iio: core: Add new DMABUF interface infrastructure

Message ID 20240308170046.92899-4-paul@crapouillou.net
State Superseded
Headers show
Series iio: new DMABUF based API | expand

Commit Message

Paul Cercueil March 8, 2024, 5 p.m. UTC 
Add the necessary infrastructure to the IIO core to support a new
optional DMABUF based interface.

With this new interface, DMABUF objects (externally created) can be
attached to a IIO buffer, and subsequently used for data transfer.

A userspace application can then use this interface to share DMABUF
objects between several interfaces, allowing it to transfer data in a
zero-copy fashion, for instance between IIO and the USB stack.

The userspace application can also memory-map the DMABUF objects, and
access the sample data directly. The advantage of doing this vs. the
read() interface is that it avoids an extra copy of the data between the
kernel and userspace. This is particularly userful for high-speed
devices which produce several megabytes or even gigabytes of data per
second.

As part of the interface, 3 new IOCTLs have been added:

IIO_BUFFER_DMABUF_ATTACH_IOCTL(int fd):
 Attach the DMABUF object identified by the given file descriptor to the
 buffer.

IIO_BUFFER_DMABUF_DETACH_IOCTL(int fd):
 Detach the DMABUF object identified by the given file descriptor from
 the buffer. Note that closing the IIO buffer's file descriptor will
 automatically detach all previously attached DMABUF objects.

IIO_BUFFER_DMABUF_ENQUEUE_IOCTL(struct iio_dmabuf *):
 Request a data transfer to/from the given DMABUF object. Its file
 descriptor, as well as the transfer size and flags are provided in the
 "iio_dmabuf" structure.

These three IOCTLs have to be performed on the IIO buffer's file
descriptor, obtained using the IIO_BUFFER_GET_FD_IOCTL() ioctl.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Nuno Sa <nuno.sa@analog.com>

---
v2: Only allow the new IOCTLs on the buffer FD created with
    IIO_BUFFER_GET_FD_IOCTL().

v3: - Get rid of the old IOCTLs. The IIO subsystem does not create or
    manage DMABUFs anymore, and only attaches/detaches externally
    created DMABUFs.
    - Add IIO_BUFFER_DMABUF_CYCLIC to the supported flags.

v5: - Use dev_err() instead of pr_err()
    - Inline to_iio_dma_fence()
    - Add comment to explain why we unref twice when detaching dmabuf
    - Remove TODO comment. It is actually safe to free the file's
      private data even when transfers are still pending because it
      won't be accessed.
    - Fix documentation of new fields in struct iio_buffer_access_funcs
    - iio_dma_resv_lock() does not need to be exported, make it static

v6: - Remove dead code in iio_dma_resv_lock()
    - Fix non-block actually blocking
    - Cache dma_buf_attachment instead of mapping/unmapping it for every
      transfer
    - Return -EINVAL instead of IIO_IOCTL_UNHANDLED for unknown ioctl
    - Make .block_enqueue() callback take a dma_fence pointer, which
      will be passed to iio_buffer_signal_dmabuf_done() instead of the
      dma_buf_attachment; and remove the backpointer from the priv
      structure to the dma_fence.
    - Use dma_fence_begin/end_signalling in the dma_fence critical
      sections
    - Unref dma_fence and dma_buf_attachment in worker, because they
      might try to lock the dma_resv, which would deadlock.
    - Add buffer ops to lock/unlock the queue. This is motivated by the
      fact that once the dma_fence has been installed, we cannot lock
      anything anymore - so the queue must be locked before the
      dma_fence is installed.
    - Use 'long retl' variable to handle the return value of
      dma_resv_wait_timeout()
    - Protect dmabufs list access with a mutex
    - Rework iio_buffer_find_attachment() to use the internal dmabufs
      list, instead of messing with dmabufs private data.
    - Add an atomically-increasing sequence number for fences

v8  - Fix swapped fence direction
    - Simplify fence wait mechanism
    - Remove "Buffer closed with active transfers" print, as it was dead
      code
    - Un-export iio_buffer_dmabuf_{get,put}. They are not used anywhere
      else so they can even be static.
    - Prevent attaching already-attached DMABUFs
---
 drivers/iio/industrialio-buffer.c | 462 ++++++++++++++++++++++++++++++
 include/linux/iio/buffer_impl.h   |  30 ++
 include/uapi/linux/iio/buffer.h   |  22 ++
 3 files changed, 514 insertions(+)

Comments

kernel test robot March 10, 2024, 12:55 a.m. UTC | #1 
Hi Paul,

kernel test robot noticed the following build errors:

[auto build test ERROR on jic23-iio/togreg]
[also build test ERROR on vkoul-dmaengine/next lwn/docs-next linus/master v6.8-rc7 next-20240308]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Paul-Cercueil/dmaengine-Add-API-function-dmaengine_prep_peripheral_dma_vec/20240309-010421
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
patch link:    https://lore.kernel.org/r/20240308170046.92899-4-paul%40crapouillou.net
patch subject: [PATCH v8 3/6] iio: core: Add new DMABUF interface infrastructure
config: nios2-randconfig-r071-20240309 (https://download.01.org/0day-ci/archive/20240310/202403100826.wjMQq4I6-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240310/202403100826.wjMQq4I6-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202403100826.wjMQq4I6-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

WARNING: modpost: missing MODULE_DESCRIPTION() in fs/nls/mac-celtic.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/nls/mac-greek.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/nls/mac-inuit.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/unicode/utf8data.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/bcachefs/mean_and_variance_test.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/jbd2/jbd2.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/fat/fat.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/fat/fat_test.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/sysv/sysv.o
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/pstore/pstore.o
WARNING: modpost: missing MODULE_DESCRIPTION() in security/keys/encrypted-keys/encrypted-keys.o
WARNING: modpost: missing MODULE_DESCRIPTION() in crypto/cast_common.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/test_ubsan.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/irqchip/irq-meson-gpio.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpio/gpio-gw-pld.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpio/gpio-pcf857x.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/pwm/pwm-visconti.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/video/fbdev/goldfishfb.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/video/fbdev/vfb.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt6765-vcodec.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt6779-mm.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt6779-cam.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-apmixedsys.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-bdp.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-img.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-jpgdec.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-mfg.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-vdec.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt2712-venc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt7622-eth.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt7622-aud.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt7986-apmixed.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt7986-topckgen.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt8167-mfgcfg.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/mediatek/clk-mt8195-mfg.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/qcom/lpass-gfm-sm8250.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/qcom/videocc-sdm845.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/suniv-f1c100s-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun20i-d1-r-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun50i-h6-r-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun6i-a31-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun9i-a80-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun9i-a80-de-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/sunxi-ng/sun9i-a80-usb-ccu.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/clk/clk-gate_test.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/regulator/da9121-regulator.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/regulator/max20411-regulator.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/tty/serial/esp32_uart.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/tty/serial/esp32_acm.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/tty/goldfish.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/char/lp.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/char/ppdev.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/base/regmap/regmap-slimbus.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/base/regmap/regmap-sccb.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/misc/fastrpc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/arizona.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dax/dax.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mtd/parsers/tplink_safeloader.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/spi/spi-altera-core.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/auxdisplay/line-display.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/host/ohci-exynos.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/class/usbtmc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/serial/mxuport.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/misc/isight_firmware.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/function/usb_f_acm.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/function/usb_f_ss_lb.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/function/u_serial.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/function/usb_f_serial.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/function/usb_f_obex.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/gadget/legacy/g_zero.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/usb/mon/usbmon.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/input/touchscreen/cyttsp_i2c_common.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/input/vivaldi-fmap.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/input/tests/input_test.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/media/rc/rc-core.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/media/dvb-frontends/mb86a16.o
WARNING: modpost: drivers/mmc/host/davinci_mmc: section mismatch in reference: davinci_mmcsd_driver+0x8 (section: .data) -> davinci_mmcsd_remove (section: .exit.text)
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/host/tmio_mmc_core.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/host/renesas_sdhi_core.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/core/mmc_core.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/core/pwrseq_simple.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/core/pwrseq_emmc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mmc/core/sdio_uart.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/leds/flash/leds-rt4505.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/crypto/xilinx/zynqmp-aes-gcm.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/staging/greybus/gb-light.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/staging/greybus/gb-log.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/staging/greybus/gb-power-supply.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/staging/greybus/gb-i2c.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/staging/greybus/gb-sdio.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/devfreq/governor_performance.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/devfreq/governor_userspace.o
WARNING: modpost: drivers/memory/emif: section mismatch in reference: emif_driver+0x8 (section: .data) -> emif_remove (section: .exit.text)
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/nvmem/nvmem_brcm_nvram.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/nvmem/nvmem_u-boot-env.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/parport/parport.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/pcmcia/pcmcia_rsrc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/adc/ingenic-adc.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/iio/buffer/kfifo_buf.o
>> ERROR: modpost: module industrialio uses symbol dma_buf_attach from namespace DMA_BUF, but does not import it.
>> ERROR: modpost: module industrialio uses symbol dma_buf_map_attachment from namespace DMA_BUF, but does not import it.
>> ERROR: modpost: module industrialio uses symbol dma_buf_unmap_attachment from namespace DMA_BUF, but does not import it.
>> ERROR: modpost: module industrialio uses symbol dma_buf_get from namespace DMA_BUF, but does not import it.
>> ERROR: modpost: module industrialio uses symbol dma_buf_put from namespace DMA_BUF, but does not import it.
>> ERROR: modpost: module industrialio uses symbol dma_buf_detach from namespace DMA_BUF, but does not import it.
kernel test robot March 10, 2024, 7:19 a.m. UTC | #2 
Hi Paul,

kernel test robot noticed the following build warnings:

[auto build test WARNING on jic23-iio/togreg]
[also build test WARNING on vkoul-dmaengine/next lwn/docs-next linus/master v6.8-rc7 next-20240308]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Paul-Cercueil/dmaengine-Add-API-function-dmaengine_prep_peripheral_dma_vec/20240309-010421
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
patch link:    https://lore.kernel.org/r/20240308170046.92899-4-paul%40crapouillou.net
patch subject: [PATCH v8 3/6] iio: core: Add new DMABUF interface infrastructure
config: i386-randconfig-062-20240309 (https://download.01.org/0day-ci/archive/20240310/202403101535.uRqo6AIt-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240310/202403101535.uRqo6AIt-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202403101535.uRqo6AIt-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/iio/industrialio-buffer.c:1765:40: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected void const [noderef] __user *from @@     got int *user_req @@
   drivers/iio/industrialio-buffer.c:1765:40: sparse:     expected void const [noderef] __user *from
   drivers/iio/industrialio-buffer.c:1765:40: sparse:     got int *user_req
>> drivers/iio/industrialio-buffer.c:1988:53: sparse: sparse: incorrect type in argument 2 (different address spaces) @@     expected int *user_req @@     got void [noderef] __user *_arg @@
   drivers/iio/industrialio-buffer.c:1988:53: sparse:     expected int *user_req
   drivers/iio/industrialio-buffer.c:1988:53: sparse:     got void [noderef] __user *_arg
   drivers/iio/industrialio-buffer.c: note: in included file (through include/linux/mmzone.h, include/linux/gfp.h, include/linux/xarray.h, ...):
   include/linux/page-flags.h:242:46: sparse: sparse: self-comparison always evaluates to false

vim +1765 drivers/iio/industrialio-buffer.c

  1755	
  1756	static int iio_buffer_detach_dmabuf(struct iio_dev_buffer_pair *ib,
  1757					    int *user_req, bool nonblock)
  1758	{
  1759		struct iio_buffer *buffer = ib->buffer;
  1760		struct iio_dev *indio_dev = ib->indio_dev;
  1761		struct iio_dmabuf_priv *priv;
  1762		struct dma_buf *dmabuf;
  1763		int dmabuf_fd, ret = -EPERM;
  1764	
> 1765		if (copy_from_user(&dmabuf_fd, user_req, sizeof(dmabuf_fd)))
  1766			return -EFAULT;
  1767	
  1768		dmabuf = dma_buf_get(dmabuf_fd);
  1769		if (IS_ERR(dmabuf))
  1770			return PTR_ERR(dmabuf);
  1771	
  1772		mutex_lock(&buffer->dmabufs_mutex);
  1773	
  1774		list_for_each_entry(priv, &buffer->dmabufs, entry) {
  1775			if (priv->attach->dev == indio_dev->dev.parent
  1776			    && priv->attach->dmabuf == dmabuf) {
  1777				list_del(&priv->entry);
  1778	
  1779				/* Unref the reference from iio_buffer_attach_dmabuf() */
  1780				iio_buffer_dmabuf_put(priv->attach);
  1781				ret = 0;
  1782				break;
  1783			}
  1784		}
  1785	
  1786		mutex_unlock(&buffer->dmabufs_mutex);
  1787		dma_buf_put(dmabuf);
  1788	
  1789		return ret;
  1790	}
  1791
kernel test robot March 10, 2024, 11:30 a.m. UTC | #3 
Hi Paul,

kernel test robot noticed the following build errors:

[auto build test ERROR on jic23-iio/togreg]
[also build test ERROR on vkoul-dmaengine/next lwn/docs-next linus/master v6.8-rc7 next-20240308]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Paul-Cercueil/dmaengine-Add-API-function-dmaengine_prep_peripheral_dma_vec/20240309-010421
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
patch link:    https://lore.kernel.org/r/20240308170046.92899-4-paul%40crapouillou.net
patch subject: [PATCH v8 3/6] iio: core: Add new DMABUF interface infrastructure
config: um-randconfig-002-20240310 (https://download.01.org/0day-ci/archive/20240310/202403101928.WWSQwfdG-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240310/202403101928.WWSQwfdG-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202403101928.WWSQwfdG-lkp@intel.com/

All errors (new ones prefixed by >>):

   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_dmabuf_release':
>> industrialio-buffer.c:(.text+0xec6): undefined reference to `dma_buf_unmap_attachment'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xf96): undefined reference to `dma_buf_detach'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xfa5): undefined reference to `dma_buf_put'
   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_signal_dmabuf_done':
>> industrialio-buffer.c:(.text+0x4a56): undefined reference to `dma_fence_signal'
   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_cleanup':
>> industrialio-buffer.c:(.text+0x64f2): undefined reference to `dma_fence_release'
   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_attach_dmabuf.isra.0':
>> industrialio-buffer.c:(.text+0x9dbf): undefined reference to `dma_fence_context_alloc'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0x9df7): undefined reference to `dma_buf_get'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0x9e38): undefined reference to `dma_buf_attach'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0x9efe): undefined reference to `dma_buf_map_attachment'
   /usr/bin/ld: industrialio-buffer.c:(.text+0xa2c1): undefined reference to `dma_buf_detach'
   /usr/bin/ld: industrialio-buffer.c:(.text+0xa2cd): undefined reference to `dma_buf_put'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xa34d): undefined reference to `dma_buf_unmap_attachment'
   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_enqueue_dmabuf':
>> industrialio-buffer.c:(.text+0xa949): undefined reference to `dma_buf_get'
   /usr/bin/ld: industrialio-buffer.c:(.text+0xa997): undefined reference to `dma_buf_put'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xac84): undefined reference to `dma_fence_init'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xad4b): undefined reference to `dma_resv_wait_timeout'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xadec): undefined reference to `dma_resv_reserve_fences'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xae2c): undefined reference to `dma_resv_add_fence'
>> /usr/bin/ld: industrialio-buffer.c:(.text+0xb0da): undefined reference to `dma_fence_release'
   /usr/bin/ld: drivers/iio/industrialio-buffer.o: in function `iio_buffer_chrdev_ioctl':
   industrialio-buffer.c:(.text+0xb833): undefined reference to `dma_buf_get'
   /usr/bin/ld: industrialio-buffer.c:(.text+0xbad0): undefined reference to `dma_buf_put'
   collect2: error: ld returned 1 exit status
diff mbox series

Patch

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index b581a7e80566..554f66619ff5 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -9,14 +9,19 @@ 
  * - Better memory allocation techniques?
  * - Alternative access techniques?
  */
+#include <linux/atomic.h>
 #include <linux/anon_inodes.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-fence.h>
+#include <linux/dma-resv.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/cdev.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 #include <linux/poll.h>
 #include <linux/sched/signal.h>
 
@@ -28,6 +33,32 @@ 
 #include <linux/iio/buffer.h>
 #include <linux/iio/buffer_impl.h>
 
+#define DMABUF_ENQUEUE_TIMEOUT_MS 5000
+
+struct iio_dma_fence;
+
+struct iio_dmabuf_priv {
+	struct list_head entry;
+	struct kref ref;
+
+	struct iio_buffer *buffer;
+	struct iio_dma_buffer_block *block;
+
+	u64 context;
+	spinlock_t lock;
+
+	struct dma_buf_attachment *attach;
+	struct sg_table *sgt;
+	enum dma_data_direction dir;
+	atomic_t seqno;
+};
+
+struct iio_dma_fence {
+	struct dma_fence base;
+	struct iio_dmabuf_priv *priv;
+	struct work_struct work;
+};
+
 static const char * const iio_endian_prefix[] = {
 	[IIO_BE] = "be",
 	[IIO_LE] = "le",
@@ -332,6 +363,8 @@  void iio_buffer_init(struct iio_buffer *buffer)
 {
 	INIT_LIST_HEAD(&buffer->demux_list);
 	INIT_LIST_HEAD(&buffer->buffer_list);
+	INIT_LIST_HEAD(&buffer->dmabufs);
+	mutex_init(&buffer->dmabufs_mutex);
 	init_waitqueue_head(&buffer->pollq);
 	kref_init(&buffer->ref);
 	if (!buffer->watermark)
@@ -1519,14 +1552,57 @@  static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
 	kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
 }
 
+static void iio_buffer_dmabuf_release(struct kref *ref)
+{
+	struct iio_dmabuf_priv *priv = container_of(ref, struct iio_dmabuf_priv, ref);
+	struct dma_buf_attachment *attach = priv->attach;
+	struct iio_buffer *buffer = priv->buffer;
+	struct dma_buf *dmabuf = attach->dmabuf;
+
+	dma_resv_lock(dmabuf->resv, NULL);
+	dma_buf_unmap_attachment(attach, priv->sgt, priv->dir);
+	dma_resv_unlock(dmabuf->resv);
+
+	buffer->access->detach_dmabuf(buffer, priv->block);
+
+	dma_buf_detach(attach->dmabuf, attach);
+	dma_buf_put(dmabuf);
+	kfree(priv);
+}
+
+static void iio_buffer_dmabuf_get(struct dma_buf_attachment *attach)
+{
+	struct iio_dmabuf_priv *priv = attach->importer_priv;
+
+	kref_get(&priv->ref);
+}
+
+static void iio_buffer_dmabuf_put(struct dma_buf_attachment *attach)
+{
+	struct iio_dmabuf_priv *priv = attach->importer_priv;
+
+	kref_put(&priv->ref, iio_buffer_dmabuf_release);
+}
+
 static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
 {
 	struct iio_dev_buffer_pair *ib = filep->private_data;
 	struct iio_dev *indio_dev = ib->indio_dev;
 	struct iio_buffer *buffer = ib->buffer;
+	struct iio_dmabuf_priv *priv, *tmp;
 
 	wake_up(&buffer->pollq);
 
+	mutex_lock(&buffer->dmabufs_mutex);
+
+	/* Close all attached DMABUFs */
+	list_for_each_entry_safe(priv, tmp, &buffer->dmabufs, entry) {
+		list_del_init(&priv->entry);
+		iio_buffer_dmabuf_put(priv->attach);
+	}
+
+	mutex_unlock(&buffer->dmabufs_mutex);
+
 	kfree(ib);
 	clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
 	iio_device_put(indio_dev);
@@ -1534,11 +1610,396 @@  static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
 	return 0;
 }
 
+static int iio_dma_resv_lock(struct dma_buf *dmabuf, bool nonblock)
+{
+	if (!nonblock)
+		return dma_resv_lock_interruptible(dmabuf->resv, NULL);
+
+	if (!dma_resv_trylock(dmabuf->resv))
+		return -EBUSY;
+
+	return 0;
+}
+
+static struct dma_buf_attachment *
+iio_buffer_find_attachment(struct iio_dev_buffer_pair *ib,
+			   struct dma_buf *dmabuf, bool nonblock)
+{
+	struct device *dev = ib->indio_dev->dev.parent;
+	struct iio_buffer *buffer = ib->buffer;
+	struct dma_buf_attachment *attach = NULL;
+	struct iio_dmabuf_priv *priv;
+
+	mutex_lock(&buffer->dmabufs_mutex);
+
+	list_for_each_entry(priv, &buffer->dmabufs, entry) {
+		if (priv->attach->dev == dev
+		    && priv->attach->dmabuf == dmabuf) {
+			attach = priv->attach;
+			break;
+		}
+	}
+
+	if (attach)
+		iio_buffer_dmabuf_get(attach);
+
+	mutex_unlock(&buffer->dmabufs_mutex);
+
+	return attach ?: ERR_PTR(-EPERM);
+}
+
+static int iio_buffer_attach_dmabuf(struct iio_dev_buffer_pair *ib,
+				    int __user *user_fd, bool nonblock)
+{
+	struct iio_dev *indio_dev = ib->indio_dev;
+	struct iio_buffer *buffer = ib->buffer;
+	struct dma_buf_attachment *attach;
+	struct iio_dmabuf_priv *priv, *each;
+	struct dma_buf *dmabuf;
+	int err, fd;
+
+	if (!buffer->access->attach_dmabuf
+	    || !buffer->access->detach_dmabuf
+	    || !buffer->access->enqueue_dmabuf)
+		return -EPERM;
+
+	if (copy_from_user(&fd, user_fd, sizeof(fd)))
+		return -EFAULT;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+	priv->context = dma_fence_context_alloc(1);
+
+	dmabuf = dma_buf_get(fd);
+	if (IS_ERR(dmabuf)) {
+		err = PTR_ERR(dmabuf);
+		goto err_free_priv;
+	}
+
+	attach = dma_buf_attach(dmabuf, indio_dev->dev.parent);
+	if (IS_ERR(attach)) {
+		err = PTR_ERR(attach);
+		goto err_dmabuf_put;
+	}
+
+	err = iio_dma_resv_lock(dmabuf, nonblock);
+	if (err)
+		goto err_dmabuf_detach;
+
+	priv->dir = buffer->direction == IIO_BUFFER_DIRECTION_IN
+		? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+	priv->sgt = dma_buf_map_attachment(attach, priv->dir);
+	if (IS_ERR(priv->sgt)) {
+		err = PTR_ERR(priv->sgt);
+		dev_err(&indio_dev->dev, "Unable to map attachment: %d\n", err);
+		goto err_resv_unlock;
+	}
+
+	kref_init(&priv->ref);
+	priv->buffer = buffer;
+	priv->attach = attach;
+	attach->importer_priv = priv;
+
+	priv->block = buffer->access->attach_dmabuf(buffer, attach);
+	if (IS_ERR(priv->block)) {
+		err = PTR_ERR(priv->block);
+		goto err_dmabuf_unmap_attachment;
+	}
+
+	dma_resv_unlock(dmabuf->resv);
+
+	mutex_lock(&buffer->dmabufs_mutex);
+
+	/*
+	 * Check whether we already have an attachment for this driver/DMABUF
+	 * combo. If we do, refuse to attach.
+	 */
+	list_for_each_entry(each, &buffer->dmabufs, entry) {
+		if (each->attach->dev == indio_dev->dev.parent
+		    && each->attach->dmabuf == dmabuf) {
+			/*
+			 * We unlocked the reservation object, so going through
+			 * the cleanup code would mean re-locking it first.
+			 * At this stage it is simpler to free the attachment
+			 * using iio_buffer_dma_put().
+			 */
+			mutex_unlock(&buffer->dmabufs_mutex);
+			iio_buffer_dmabuf_put(attach);
+			return -EBUSY;
+		}
+	}
+
+	/* Otherwise, add the new attachment to our dmabufs list. */
+	list_add(&priv->entry, &buffer->dmabufs);
+	mutex_unlock(&buffer->dmabufs_mutex);
+
+	return 0;
+
+err_dmabuf_unmap_attachment:
+	dma_buf_unmap_attachment(attach, priv->sgt, priv->dir);
+err_resv_unlock:
+	dma_resv_unlock(dmabuf->resv);
+err_dmabuf_detach:
+	dma_buf_detach(dmabuf, attach);
+err_dmabuf_put:
+	dma_buf_put(dmabuf);
+err_free_priv:
+	kfree(priv);
+
+	return err;
+}
+
+static int iio_buffer_detach_dmabuf(struct iio_dev_buffer_pair *ib,
+				    int *user_req, bool nonblock)
+{
+	struct iio_buffer *buffer = ib->buffer;
+	struct iio_dev *indio_dev = ib->indio_dev;
+	struct iio_dmabuf_priv *priv;
+	struct dma_buf *dmabuf;
+	int dmabuf_fd, ret = -EPERM;
+
+	if (copy_from_user(&dmabuf_fd, user_req, sizeof(dmabuf_fd)))
+		return -EFAULT;
+
+	dmabuf = dma_buf_get(dmabuf_fd);
+	if (IS_ERR(dmabuf))
+		return PTR_ERR(dmabuf);
+
+	mutex_lock(&buffer->dmabufs_mutex);
+
+	list_for_each_entry(priv, &buffer->dmabufs, entry) {
+		if (priv->attach->dev == indio_dev->dev.parent
+		    && priv->attach->dmabuf == dmabuf) {
+			list_del(&priv->entry);
+
+			/* Unref the reference from iio_buffer_attach_dmabuf() */
+			iio_buffer_dmabuf_put(priv->attach);
+			ret = 0;
+			break;
+		}
+	}
+
+	mutex_unlock(&buffer->dmabufs_mutex);
+	dma_buf_put(dmabuf);
+
+	return ret;
+}
+
+static const char *
+iio_buffer_dma_fence_get_driver_name(struct dma_fence *fence)
+{
+	return "iio";
+}
+
+static void iio_buffer_dma_fence_release(struct dma_fence *fence)
+{
+	struct iio_dma_fence *iio_fence =
+		container_of(fence, struct iio_dma_fence, base);
+
+	kfree(iio_fence);
+}
+
+static const struct dma_fence_ops iio_buffer_dma_fence_ops = {
+	.get_driver_name	= iio_buffer_dma_fence_get_driver_name,
+	.get_timeline_name	= iio_buffer_dma_fence_get_driver_name,
+	.release		= iio_buffer_dma_fence_release,
+};
+
+static int iio_buffer_enqueue_dmabuf(struct iio_dev_buffer_pair *ib,
+				     struct iio_dmabuf __user *iio_dmabuf_req,
+				     bool nonblock)
+{
+	struct iio_buffer *buffer = ib->buffer;
+	struct iio_dmabuf iio_dmabuf;
+	struct dma_buf_attachment *attach;
+	struct iio_dmabuf_priv *priv;
+	struct iio_dma_fence *fence;
+	struct dma_buf *dmabuf;
+	unsigned long timeout;
+	bool cookie, cyclic, dma_to_ram;
+	long retl;
+	u32 seqno;
+	int ret;
+
+	if (copy_from_user(&iio_dmabuf, iio_dmabuf_req, sizeof(iio_dmabuf)))
+		return -EFAULT;
+
+	if (iio_dmabuf.flags & ~IIO_BUFFER_DMABUF_SUPPORTED_FLAGS)
+		return -EINVAL;
+
+	cyclic = iio_dmabuf.flags & IIO_BUFFER_DMABUF_CYCLIC;
+
+	/* Cyclic flag is only supported on output buffers */
+	if (cyclic && buffer->direction != IIO_BUFFER_DIRECTION_OUT)
+		return -EINVAL;
+
+	dmabuf = dma_buf_get(iio_dmabuf.fd);
+	if (IS_ERR(dmabuf))
+		return PTR_ERR(dmabuf);
+
+	if (!iio_dmabuf.bytes_used || iio_dmabuf.bytes_used > dmabuf->size) {
+		ret = -EINVAL;
+		goto err_dmabuf_put;
+	}
+
+	attach = iio_buffer_find_attachment(ib, dmabuf, nonblock);
+	if (IS_ERR(attach)) {
+		ret = PTR_ERR(attach);
+		goto err_dmabuf_put;
+	}
+
+	priv = attach->importer_priv;
+
+	fence = kmalloc(sizeof(*fence), GFP_KERNEL);
+	if (!fence) {
+		ret = -ENOMEM;
+		goto err_attachment_put;
+	}
+
+	fence->priv = priv;
+
+	seqno = atomic_add_return(1, &priv->seqno);
+
+	/*
+	 * The transfers are guaranteed to be processed in the order they are
+	 * enqueued, so we can use a simple incrementing sequence number for
+	 * the dma_fence.
+	 */
+	dma_fence_init(&fence->base, &iio_buffer_dma_fence_ops,
+		       &priv->lock, priv->context, seqno);
+
+	ret = iio_dma_resv_lock(dmabuf, nonblock);
+	if (ret)
+		goto err_fence_put;
+
+	timeout = nonblock ? 0 : msecs_to_jiffies(DMABUF_ENQUEUE_TIMEOUT_MS);
+	dma_to_ram = buffer->direction == IIO_BUFFER_DIRECTION_IN;
+
+	/* Make sure we don't have writers */
+	retl = dma_resv_wait_timeout(dmabuf->resv,
+				     dma_resv_usage_rw(dma_to_ram),
+				     true, timeout);
+	if (retl == 0)
+		retl = -EBUSY;
+	if (retl < 0) {
+		ret = (int)retl;
+		goto err_resv_unlock;
+	}
+
+	if (buffer->access->lock_queue)
+		buffer->access->lock_queue(buffer);
+
+	ret = dma_resv_reserve_fences(dmabuf->resv, 1);
+	if (ret)
+		goto err_queue_unlock;
+
+	dma_resv_add_fence(dmabuf->resv, &fence->base,
+			   dma_to_ram ? DMA_RESV_USAGE_WRITE : DMA_RESV_USAGE_READ);
+	dma_resv_unlock(dmabuf->resv);
+
+	cookie = dma_fence_begin_signalling();
+
+	ret = buffer->access->enqueue_dmabuf(buffer, priv->block, &fence->base,
+					     priv->sgt, iio_dmabuf.bytes_used,
+					     cyclic);
+	if (ret) {
+		/*
+		 * DMABUF enqueue failed, but we already added the fence.
+		 * Signal the error through the fence completion mechanism.
+		 */
+		iio_buffer_signal_dmabuf_done(&fence->base, ret);
+	}
+
+	if (buffer->access->unlock_queue)
+		buffer->access->unlock_queue(buffer);
+
+	dma_fence_end_signalling(cookie);
+	dma_buf_put(dmabuf);
+
+	return ret;
+
+err_queue_unlock:
+	if (buffer->access->unlock_queue)
+		buffer->access->unlock_queue(buffer);
+err_resv_unlock:
+	dma_resv_unlock(dmabuf->resv);
+err_fence_put:
+	dma_fence_put(&fence->base);
+err_attachment_put:
+	iio_buffer_dmabuf_put(attach);
+err_dmabuf_put:
+	dma_buf_put(dmabuf);
+
+	return ret;
+}
+
+static void iio_buffer_cleanup(struct work_struct *work)
+{
+	struct iio_dma_fence *fence =
+		container_of(work, struct iio_dma_fence, work);
+	struct iio_dmabuf_priv *priv = fence->priv;
+	struct dma_buf_attachment *attach = priv->attach;
+
+	dma_fence_put(&fence->base);
+	iio_buffer_dmabuf_put(attach);
+}
+
+void iio_buffer_signal_dmabuf_done(struct dma_fence *fence, int ret)
+{
+	struct iio_dma_fence *iio_fence =
+		container_of(fence, struct iio_dma_fence, base);
+	bool cookie = dma_fence_begin_signalling();
+
+	/*
+	 * Get a reference to the fence, so that it's not freed as soon as
+	 * it's signaled.
+	 */
+	dma_fence_get(fence);
+
+	fence->error = ret;
+	dma_fence_signal(fence);
+	dma_fence_end_signalling(cookie);
+
+	/*
+	 * The fence will be unref'd in iio_buffer_cleanup.
+	 * It can't be done here, as the unref functions might try to lock the
+	 * resv object, which can deadlock.
+	 */
+	INIT_WORK(&iio_fence->work, iio_buffer_cleanup);
+	schedule_work(&iio_fence->work);
+}
+EXPORT_SYMBOL_GPL(iio_buffer_signal_dmabuf_done);
+
+static long iio_buffer_chrdev_ioctl(struct file *filp,
+				    unsigned int cmd, unsigned long arg)
+{
+	struct iio_dev_buffer_pair *ib = filp->private_data;
+	void __user *_arg = (void __user *)arg;
+	bool nonblock = filp->f_flags & O_NONBLOCK;
+
+	switch (cmd) {
+	case IIO_BUFFER_DMABUF_ATTACH_IOCTL:
+		return iio_buffer_attach_dmabuf(ib, _arg, nonblock);
+	case IIO_BUFFER_DMABUF_DETACH_IOCTL:
+		return iio_buffer_detach_dmabuf(ib, _arg, nonblock);
+	case IIO_BUFFER_DMABUF_ENQUEUE_IOCTL:
+		return iio_buffer_enqueue_dmabuf(ib, _arg, nonblock);
+	default:
+		return -EINVAL;
+	}
+}
+
 static const struct file_operations iio_buffer_chrdev_fileops = {
 	.owner = THIS_MODULE,
 	.llseek = noop_llseek,
 	.read = iio_buffer_read,
 	.write = iio_buffer_write,
+	.unlocked_ioctl = iio_buffer_chrdev_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
 	.poll = iio_buffer_poll,
 	.release = iio_buffer_chrdev_release,
 };
@@ -1953,6 +2414,7 @@  static void iio_buffer_release(struct kref *ref)
 {
 	struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
 
+	mutex_destroy(&buffer->dmabufs_mutex);
 	buffer->access->release(buffer);
 }
 
diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
index 89c3fd7c29ca..1a221c1d7736 100644
--- a/include/linux/iio/buffer_impl.h
+++ b/include/linux/iio/buffer_impl.h
@@ -9,8 +9,12 @@ 
 #include <uapi/linux/iio/buffer.h>
 #include <linux/iio/buffer.h>
 
+struct dma_buf_attachment;
+struct dma_fence;
 struct iio_dev;
+struct iio_dma_buffer_block;
 struct iio_buffer;
+struct sg_table;
 
 /**
  * INDIO_BUFFER_FLAG_FIXED_WATERMARK - Watermark level of the buffer can not be
@@ -39,6 +43,13 @@  struct iio_buffer;
  *                      device stops sampling. Calles are balanced with @enable.
  * @release:		called when the last reference to the buffer is dropped,
  *			should free all resources allocated by the buffer.
+ * @attach_dmabuf:	called from userspace via ioctl to attach one external
+ *			DMABUF.
+ * @detach_dmabuf:	called from userspace via ioctl to detach one previously
+ *			attached DMABUF.
+ * @enqueue_dmabuf:	called from userspace via ioctl to queue this DMABUF
+ *			object to this buffer. Requires a valid DMABUF fd, that
+ *			was previouly attached to this buffer.
  * @modes:		Supported operating modes by this buffer type
  * @flags:		A bitmask combination of INDIO_BUFFER_FLAG_*
  *
@@ -68,6 +79,17 @@  struct iio_buffer_access_funcs {
 
 	void (*release)(struct iio_buffer *buffer);
 
+	struct iio_dma_buffer_block * (*attach_dmabuf)(struct iio_buffer *buffer,
+						       struct dma_buf_attachment *attach);
+	void (*detach_dmabuf)(struct iio_buffer *buffer,
+			      struct iio_dma_buffer_block *block);
+	int (*enqueue_dmabuf)(struct iio_buffer *buffer,
+			      struct iio_dma_buffer_block *block,
+			      struct dma_fence *fence, struct sg_table *sgt,
+			      size_t size, bool cyclic);
+	void (*lock_queue)(struct iio_buffer *buffer);
+	void (*unlock_queue)(struct iio_buffer *buffer);
+
 	unsigned int modes;
 	unsigned int flags;
 };
@@ -136,6 +158,12 @@  struct iio_buffer {
 
 	/* @ref: Reference count of the buffer. */
 	struct kref ref;
+
+	/* @dmabufs: List of DMABUF attachments */
+	struct list_head dmabufs; /* P: dmabufs_mutex */
+
+	/* @dmabufs_mutex: Protects dmabufs */
+	struct mutex dmabufs_mutex;
 };
 
 /**
@@ -159,6 +187,8 @@  void iio_buffer_init(struct iio_buffer *buffer);
 struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer);
 void iio_buffer_put(struct iio_buffer *buffer);
 
+void iio_buffer_signal_dmabuf_done(struct dma_fence *fence, int ret);
+
 #else /* CONFIG_IIO_BUFFER */
 
 static inline void iio_buffer_get(struct iio_buffer *buffer) {}
diff --git a/include/uapi/linux/iio/buffer.h b/include/uapi/linux/iio/buffer.h
index 13939032b3f6..c666aa95e532 100644
--- a/include/uapi/linux/iio/buffer.h
+++ b/include/uapi/linux/iio/buffer.h
@@ -5,6 +5,28 @@ 
 #ifndef _UAPI_IIO_BUFFER_H_
 #define _UAPI_IIO_BUFFER_H_
 
+#include <linux/types.h>
+
+/* Flags for iio_dmabuf.flags */
+#define IIO_BUFFER_DMABUF_CYCLIC		(1 << 0)
+#define IIO_BUFFER_DMABUF_SUPPORTED_FLAGS	0x00000001
+
+/**
+ * struct iio_dmabuf - Descriptor for a single IIO DMABUF object
+ * @fd:		file descriptor of the DMABUF object
+ * @flags:	one or more IIO_BUFFER_DMABUF_* flags
+ * @bytes_used:	number of bytes used in this DMABUF for the data transfer.
+ *		Should generally be set to the DMABUF's size.
+ */
+struct iio_dmabuf {
+	__u32 fd;
+	__u32 flags;
+	__u64 bytes_used;
+};
+
 #define IIO_BUFFER_GET_FD_IOCTL			_IOWR('i', 0x91, int)
+#define IIO_BUFFER_DMABUF_ATTACH_IOCTL		_IOW('i', 0x92, int)
+#define IIO_BUFFER_DMABUF_DETACH_IOCTL		_IOW('i', 0x93, int)
+#define IIO_BUFFER_DMABUF_ENQUEUE_IOCTL		_IOW('i', 0x94, struct iio_dmabuf)
 
 #endif /* _UAPI_IIO_BUFFER_H_ */