On Saturday, September 11, 2010 16:10:52 Andy Walls wrote:
> On Sat, 2010-09-11 at 15:49 +0200, Hans Verkuil wrote:
> > I'm working on the V4L2 DocBook spec and when reading through the "Device
> > Naming"
> > subsection of the "Opening and Closing Devices" section in the first
> > chapter I
> > realized that it is really out of date. The text is in this file:
> >
> > Documentation/DocBook/v4l/common.xml
> >
> > With udev pretty much everything in that section is useless (and probably
> > confusing
> > for first-time readers).
> >
> > I propose that we replace it with something short like this:
> >
> > -----------------------------------------------------
> > Device Naming
> >
> > V4L2 drivers create one or more device nodes with major number 81 and a
> > minor number
> > between 0 and 255. Three types of devices can be created:
> >
> > /dev/videoX Used for video capture/output/overlay.
>
> PCM audio capture
I don't really dare mention this :-) This really should have been an alsa
device.
PCM audio capture is really a big hack. This is a topic for a v4l summit to
decide what to do with this. And I guess it depends on whether alsa can be
extended with proper time stamping.
> MPEG index (metadata)
I think is a bit too detailed for an overview section.
>
> > /dev/radioX Used for radio and RDS tuning/modulating.
> > /dev/vbiX Used for VBI capture and output.
> > -----------------------------------------------------
> >
> > Is there anything else that should be in here?
>
> You may want to mention, without fully specifying, that V4L2 drivers can
> present ALSA device nodes as well.
This is covered in the 'Related Devices' section.
> I don't think the V4L2 drivers have a really uniform convention for
> their "card" name exported to ALSA nor the ALSA mixer control names.
>
> To document the Media Controller, the document will eventually have to
> mention ALSA, framebuffer, LED, etc. APIs anyway.
Of course.
Regards,
Hans
>
>
> > BTW, I'm working on editing the 'Related Devices', 'Multiple Opens' and
> > 'Shared Data Streams' as well.
> >
> > Regards,
> >
> > Hans
>
> Regards,
> Andy
>
>
>
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG, part of Cisco
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