Em Fri, 8 May 2020 15:24:33 +0200 Hans Verkuil <hverkuil-cisco@xxxxxxxxx> escreveu: > On 08/05/2020 15:10, Mauro Carvalho Chehab wrote: > > Right now, only kAPI documentation describes the device naming. > > However, such description is needed at the uAPI too. Add it, > > and describe how to get an unique identify for a given device. > > identifier > > > > > Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx> > > --- > > .../userspace-api/media/v4l/open.rst | 43 +++++++++++++++++-- > > 1 file changed, 40 insertions(+), 3 deletions(-) > > > > diff --git a/Documentation/userspace-api/media/v4l/open.rst b/Documentation/userspace-api/media/v4l/open.rst > > index 38046ef20141..86816b247a17 100644 > > --- a/Documentation/userspace-api/media/v4l/open.rst > > +++ b/Documentation/userspace-api/media/v4l/open.rst > > @@ -14,12 +14,14 @@ Opening and Closing Devices > > *************************** > > > > > > -Device Naming > > -============= > > +.. _v4l2_device_naming: > > + > > +V4L2 Device Node Naming > > +======================= > > > > V4L2 drivers are implemented as kernel modules, loaded manually by the > > system administrator or automatically when a device is first discovered. > > -The driver modules plug into the "videodev" kernel module. It provides > > +The driver modules plug into the ``videodev`` kernel module. It provides > > helper functions and a common application interface specified in this > > document. > > > > @@ -30,6 +32,41 @@ option CONFIG_VIDEO_FIXED_MINOR_RANGES. In that case minor numbers > > are allocated in ranges depending on the device node type (video, radio, > > etc.). > > > > +The device nodes supported by the Video4Linux subsystem are: > > + > > +======================== ====================================================== > > +Default device node name Usage > > +======================== ====================================================== > > +``/dev/videoX`` Video input/output devices > > Also metadata input/output devices. > > I would prefer capture/output given the traditional names that V4L2 uses. > > > +``/dev/vbiX`` Vertical blank data (i.e. closed captions, teletext) > > +``/dev/radioX`` Radio tuners and modulators > > +``/dev/swradioX`` Software Defined Radio tuners and modulators > > +``/dev/v4l-touchX`` Touch sensors > > +``/dev/v4l-sudevX`` Video sub-devices (used by sensors and other I2C > > sudevX -> subdevX > > You made this typo in more places, it's best to search and replace. > > > + devices)\ [#]_ > > That suggests that subdevs are i2c devices, they can be any processing block on > any bus. For all the above: Ok. Will address at the next version. > > > +======================== ====================================================== > > + > > +Where ``X`` is a non-negative number. > > + > > +.. note:: > > + > > + 1. The actual device node name is system-dependent, as udev rules may apply. > > + 2. There is no guarantee that ``X`` will remain the same for the same > > + device, as the number depends on the device driver's probe order. > > + If you need an unique name, udev default rules produce > > + ``/dev/v4l/by-id/`` and ``/dev/v4l/by-path/`` directories containing > > + links that can be used uniquely to identify a V4L2 device node:: > > + > > + $ tree /dev/v4l > > + /dev/v4l > > + ├── by-id > > + │ └── usb-OmniVision._USB_Camera-B4.04.27.1-video-index0 -> ../../video0 > > + └── by-path > > + └── pci-0000:00:14.0-usb-0:2:1.0-video-index0 -> ../../video0 > > + > > +.. [#] **V4L2 sub-device nodes** (e. g. ``/dev/v4l-sudevX``) use a different > > + set of system calls, as covered at :ref:`subdev`. > > + > > Many drivers support "video_nr", "radio_nr" or "vbi_nr" module > > options to select specific video/radio/vbi node numbers. This allows the > > user to request that the device node is named e.g. /dev/video5 instead > > It looks like there is a missing period at the end of the sentence. The full sentence here is: Many drivers support "video_nr", "radio_nr" or "vbi_nr" module options to select specific video/radio/vbi node numbers. This allows the user to request that the device node is named e.g. /dev/video5 instead of leaving it to chance. When the driver supports multiple devices of the same type more than one device node number can be assigned, separated by commas: This paragraph (untouched by this patch) sounds ok to me ;-) Thanks, Mauro
