Re: em28xx + ov2640 and v4l2-clk

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Em Tue, 20 Aug 2013 15:38:57 +0200
Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> escreveu:

> 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@xxxxxx>
> > 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@xxxxxx>
> >     Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> >     Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >     Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> > 
> > (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) ?

Well, it is simple: we should either revert the patch(es) that broke it or
someone should fix it at em28xx. If nobody could fix it, I'll just revert
the patches that broke it and ask -stable to do the same.

Btw, 3.10 is a long term stable, so, it is not too late for fixes there.

> 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.

Ok, but this doesn't solve one issue: who would do it and when.

Cheers,
Mauro
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