Hi Sakari, Em Tue, 29 Aug 2017 11:34:06 +0300 Sakari Ailus <sakari.ailus@xxxxxx> escreveu: > Hi Mauro, > > On Mon, Aug 28, 2017 at 09:53:56AM -0300, 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. > > > > Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx> > > --- > > Documentation/media/uapi/v4l/open.rst | 39 ++++++++++++++++++++++++++++++++--- > > 1 file changed, 36 insertions(+), 3 deletions(-) > > > > diff --git a/Documentation/media/uapi/v4l/open.rst b/Documentation/media/uapi/v4l/open.rst > > index afd116edb40d..fc0037091814 100644 > > --- a/Documentation/media/uapi/v4l/open.rst > > +++ b/Documentation/media/uapi/v4l/open.rst > > @@ -7,12 +7,14 @@ 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. > > > > @@ -23,6 +25,37 @@ 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 existing V4L2 device node types are: > > + > > +======================== ====================================================== > > +Default device node name Usage > > +======================== ====================================================== > > +``/dev/videoX`` Video input/output devices > > +``/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 > > Should we document V4L2 sub-device nodes here as well? They are implemented > by the V4L2 core as well as the other device node types. > > Their purpose is somewhat different, though, and I think we'll need to make > that explicit somehow. Actually, what we're calling as "V4L2 Device node" are the vdev-centric device nodes. That should not include /dev/v4l-subdevX. What we can do here is to explicitly rule out the subdev interfaces, with something like: .. note:: 3. **V4L2 sub-device nodes** (e. g. ``/dev/v4l-sudevX``) provide a different API and aren't considered as V4L2 device nodes. They are covered at :ref:`subdev`. > > > +======================== ====================================================== > > + > > +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 warranty that ``X`` will remain the same for the same > > s/warranty/guarantee/ OK. > > > + 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/`` directoiries containing > > "directories" OK. > > > + 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 > > + > > + > > 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 > Thanks, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
