Re: [PATCH 1/2] media: V4L2: add temporary clock helpers

Laurent Pinchart
2012-10-26T02:05:00Z

Hello,

On Sunday 21 October 2012 20:52:21 Sylwester Nawrocki wrote:
> On 10/20/2012 12:20 AM, Guennadi Liakhovetski wrote:
> > Typical video devices like camera sensors require an external clock
> > source. Many such devices cannot even access their hardware registers
> > without a running clock. These clock sources should be controlled by their
> > consumers. This should be performed, using the generic clock framework.
> > Unfortunately so far only very few systems have been ported to that
> > framework. This patch adds a set of temporary helpers, mimicking the
> > generic clock API, to V4L2. Platforms, adopting the clock API, should
> > switch to using it. Eventually this temporary API should be removed.
>
> So I gave this patch a try this weekend. I would have a few comments/
> questions. Thank you for sharing this!

I've finally found time to give it a try, and I can report successful results.

My development target here is a Beagleboard-xM with an MT9P031 sensor. With
this patch and Sylwester's additional patches [1], I've been able to remove
the board code callback from the mt9p031 driver platform data, as well as the
last omap3-isp platform callback.

The result is available in the devel/v4l2-clock branch of
http://git.linuxtv.org/pinchartl/media.git. Sylwester, that branch includes a
minor fix titled "v4l2-clk: Fix clock id matching" for your "v4l2-clk: Rework
to accept more than one clock with null clock id" patch. Could you please have
a look at it ?

On the downside, there's now a circular dependency between the mt9p031 and
omap3-isp drivers, so neither of them can be removed. That will need to be
fixed.

[1] http://git.linuxtv.org/snawrocki/media.git/shortlog/refs/heads/s3c-camif-
devel

--
Regards,

Laurent Pinchart