[PATCH v4 2/5] media: ov2640: add async probe function

[g.liakhovetski@gmx.de (Guennadi Liakhovetski)]

Hi Laurent,

First of all, sorry, I am currently on a holiday, so, replies are delayed, 
real work (reviewing or anything else) is impossible.

On Tue, 30 Dec 2014, Laurent Pinchart wrote:

> Hi Guennadi,
> 
> On Friday 26 December 2014 11:38:11 Guennadi Liakhovetski wrote:
> > On Fri, 26 Dec 2014, Laurent Pinchart wrote:
> > > On Friday 26 December 2014 10:14:26 Guennadi Liakhovetski wrote:
> > >> On Fri, 26 Dec 2014, Laurent Pinchart wrote:
> > >>> On Friday 26 December 2014 14:37:14 Josh Wu wrote:
> 
> [snip]
> 
> > >>> Talking about mclk and xvclk is quite confusing. There's no mclk from
> > >>> an ov2640 point of view. The ov2640 driver should call
> > >>> v4l2_clk_get("xvclk").
> > >> 
> > >> Yes, I also was thinking about this, and yes, requesting a "xvclk" clock
> > >> would be more logical. But then, as you write below, if we let the
> > >> v4l2_clk wrapper first check for a CCF "xvclk" clock, say, none is
> > >> found. How do we then find the exported "mclk" V4L2 clock? Maybe
> > >> v4l2_clk_get() should use two names?..
> > > 
> > > Given that v4l2_clk_get() is only used by soc-camera drivers and that they
> > > all call it with the clock name set to "mclk", I wonder whether we
> > > couldn't just get rid of struct v4l2_clk.id and ignore the id argument to
> > > v4l2_clk_get() when CCF isn't available. Maybe we've overdesigned
> > > v4l2_clk :-)
> > 
> > Sure, that'd be fine with me, if everyone else agrees.
> 
> Can you submit a patch ? That's the best way to find out if anyone objects.

Can do, sure, once I am back home and find time for this.

> [snip]
> 
> > >>> v4l2_clk_get() should try to get the clock from CCF with a call to
> > >>> clk_get() first, and then look at the list of v4l2-specific clocks.
> > >> 
> > >> Yes, how will it find the "mclk" when "xvclk" (or any other name) is
> > >> requested? We did discuss this in the beginning and agreed to use a
> > >> fixed clock name for the time being...
> > > 
> > > Please see above.
> > > 
> > >>> That's at least how I had envisioned it when v4l2_clk_get() was
> > >>> introduced. Let's remember that v4l2_clk was designed as a temporary
> > >>> workaround for platforms not implementing CCF yet. Is that still
> > >>> needed,
> > >>> or could be instead just get rid of it now ?
> > >> 
> > >> I didn't check, but I don't think all platforms, handled by soc-camera,
> > >> support CCF yet.
> > > 
> > > After a quick check it looks like only OMAP1 and SH Mobile are missing.
> > > Atmel, MX2, MX3 and R-Car all support CCF. PXA27x has CCF support but
> > > doesn't enable it yet for an unknown (to me) reason.
> > > 
> > > The CEU driver is used on both arch/sh and arch/arm/mach-shmobile. The
> > > former will most likely never receive CCF support, and the latter is
> > > getting fixed. As arch/sh isn't maintained anymore I would be fine with
> > > dropping CEU support for it.
> > > 
> > > OMAP1 is thus the only long-term show-stopper. What should we do with it ?
> > 
> > Indeed, what should we? :)
> 
> You're listed as the soc-camera maintainer, so you should provide an answer to 
> that question :-)

Thanks for ar reminder;)

> I'll propose one, let's drop the omap1-camera driver (I've 
> CC'ed the original author of the driver to this e-mail).

Let's see what they reply, but I don't tgink Josh will want to wait that 
long. And until omap1 is in the mainline we cannot drop v4l2_clk.

Thanks
Guennadi

> 
> -- 
> Regards,
> 
> Laurent Pinchart
>