Re: [PATCH] Fix suspend/resume of pxa_camera driver

Guennadi Liakhovetski
2008-07-29T17:16:24Z

On Mon, 28 Jul 2008, Robert Jarzmik wrote:

> Guennadi Liakhovetski <g.liakhovetski@gmx.de> writes:
>
> > On Sun, 27 Jul 2008, Robert Jarzmik wrote:
> >
> > Yes, this is the difference. The sensor is attached to the camera host
> > only on open. In fact, I am not sure, how video applications should behave
> > during a suspend / resume cycle. If you suspend, while, say, recording
> > from your camera, should you directly continue recording after a wake up?
> > How do currect drivers implement this? Or, in general, for example with
> > audio - if you suspend while listening to a stream over the net, or to a
> > CD, or to a mp3-file on your local disk, should the sound resume after a
> > wake up? I added linux-pm for some authoritative answers:-)
> AFAIK, on resume, sound streams continues. So the normal behaviour would be to
> continue video stream too (as done in ALSA). This supposes the whole video chip
> state is saved on suspend and restored on resume, of course.

Ok, that's what I also thought.

> > If you know how a v4l2 device should handle suspend/resume, or when we get
> > some answers, let's try to do it completely-
> Of course. In a week or two, my mt9m111 driver will be ready for submission, and
> in the review process I'll post a submission for complete suspend/resume.
>
> >> For the camera part, by now, I'm using standard suspend/resume functions of the
> >> platform driver (mt9m111.c). It does work, but it's not clean ATM. The chaining
> >> between the driver resume function and the availability of the I2C bus are not
> >> properly chained. I'm still working on it.
> >
> > Yes, we have to clarify this too.
> Yes.
>
> So, to sum up :
> - I finish the mt9m111 driver
> - I submit it
> - I cook up a clean suspend/resume (unless you did it first of course :)

Good plan! You don't have to worry - I will not do this before you:-)

And, I am still waiting for the patch to move .power and .reset to
camera-link (see my another post on the V4L ML today). With that patch in
place your power-management would also become easier and more logical.

Thanks
Guennadi
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Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer