Re: [PATCH v8 1/7] media: V4L2: add temporary clock helpers

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

Hi Mike,

On Thursday 11 April 2013 16:19:23 Mike Turquette wrote:
> Quoting Laurent Pinchart (2013-04-11 15:35:38)
> > On Thursday 11 April 2013 11:52:58 Mike Turquette wrote:

[snip]

> > > I came into this thread late and don't have the actual patches in my
> > > inbox for review.  That said, I don't understand why V4L2 cares about
> > > the clk framework *implementation*?  The clk.h api is the same for
> > > platforms using the common struct clk and those still using the legacy
> > > method of defining their own struct clk.  If drivers are only consumers
> > > of the clk.h api then the implementation underneath should not matter.
> > 
> > The issue on non-CCF systems is that devices usually can't register clocks
> > dynamically. (Most of) those systems provide system clocks only through
> > their clock API, without a way for the camera IP core to hook up the
> > clock(s) it can provide to the camera sensor. On the consumer side we
> > don't care much about the clock framework implementation, but on the
> > provider side we need a framework that allows registering non-system
> > clocks at runtime.
> 
> Yes, you do care about the clock framework implementation if you are a clock
> provider.  I still haven't gone through the archives to find these patches
> but I hope that any dependency on CONFIG_COMMON_CLK is conditionalized to
> have the smallest impact possible. Making v4l2 as a whole depend on
> COMMON_CLK might be a bit overkill compared to just making individual camera
> drivers depend on it.

The basic idea is to push the dependency on CONFIG_COMMON_CLK to individual 
drivers, and provide a V4L2-specific clock framework (that looks like a 
stripped-down version of CCF) for platforms that don't implement CCF yet.

-- 
Regards,

Laurent Pinchart