> On Mon, 8 Feb 2010, Mauro Carvalho Chehab wrote:
>
>> In fact, on all drivers, there are devices that needs to be turn on only
>> when
>> streaming is happening: sensors, analog TV/audio demods, digital demods.
>> Also,
>> a few devices (for example: TV tuners) could eventually be on power off
>> when
>> no device is opened.
>>
>> As the V4L core knows when this is happening (due to
>> open/close/poll/streamon/reqbuf/qbuf/dqbuf hooks, I think the runtime
>> management
>> can happen at V4L core level.
>
> Well, we can move it up to v4l core. Should it get any more complicated
> than adding
>
> ret = pm_runtime_resume(&vdev->dev);
> if (ret < 0 && ret != -ENOSYS)
> return ret;
>
> to v4l2_open() and
>
> pm_runtime_suspend(&vdev->dev);
>
> to v4l2_release()?
My apologies if I say something stupid as I know little about pm: are you
assuming here that streaming only happens on one device node? That may be
true for soc-camera, but other devices can have multiple streaming nodes
(video, vbi, mpeg, etc). So the call to v4l2_release does not necessarily
mean that streaming has stopped.
Regards,
Hans
> And to agree, that video drivers may set a device type
> to implement runtime PM, and that the v4l core shouldn't touch it? Then,
> for example, a bridge driver could implement such a device type instance
> and suspend or resume all related components?
>
> Thanks
> Guennadi
> ---
> Guennadi Liakhovetski, Ph.D.
> Freelance Open-Source Software Developer
> http://www.open-technology.de/
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--
Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom
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