Re: em28xx + ov2640 and v4l2-clk

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Mauro,

On Sunday 18 August 2013 12:20:08 Mauro Carvalho Chehab wrote:
> Em Sun, 18 Aug 2013 13:40:25 +0200 Frank Schäfer escreveu:
> > Am 17.08.2013 12:51, schrieb Guennadi Liakhovetski:
> > > Hi Frank,
> > > As I mentioned on the list, I'm currently on a holiday, so, replying
> > > briefly.
> >
> > Sorry, I missed that (can't read all mails on the list).
> > 
> > > Since em28xx is a USB device, I conclude, that it's supplying clock to
> > > its components including the ov2640 sensor. So, yes, I think the driver
> > > should export a V4L2 clock.
> >
> > Ok, so it's mandatory on purpose ?
> > I'll take a deeper into the v4l2-clk code and the
> > em28xx/ov2640/soc-camera interaction this week.
> > Have a nice holiday !
> 
> commit 9aea470b399d797e88be08985c489855759c6c60
> Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Date:   Fri Dec 21 13:01:55 2012 -0300
> 
>     [media] soc-camera: switch I2C subdevice drivers to use v4l2-clk
> 
>     Instead of centrally enabling and disabling subdevice master clocks in
>     soc-camera core, let subdevice drivers do that themselves, using the
>     V4L2 clock API and soc-camera convenience wrappers.
> 
>     Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
>     Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
>     Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>     Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
> 
> (c/c the ones that acked with this broken changeset)
> 
> We need to fix it ASAP or to revert the ov2640 changes, as some em28xx
> cameras are currently broken on 3.10.
> 
> I'll also reject other ports to the async API if the drivers are
> used outside an embedded driver, as no PC driver currently defines
> any clock source. The same applies to regulators.
> 
> Guennadi,
> 
> Next time, please check if the i2c drivers are used outside soc_camera
> and apply the fixes where needed, as no regressions are allowed.

We definitely need to check all users of our sensor drivers when making such a 
change. Mistakes happen, so let's fix them.

Guennadi is on holidays until the end of this week. Would that be too late to 
fix the issue (given that 3.10 is already broken) ? The fix shouldn't be too 
complex, registering a dummy V4L2 clock in the em28xx driver should be enough. 
v4l2-clk.c should provide a helper function to do so as that will be a pretty 
common operation.

-- 
Regards,

Laurent Pinchart