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

[Guennadi Liakhovetski]

On Thu, 11 Apr 2013, Barry Song wrote:

> 2013/4/11 Guennadi Liakhovetski <g.liakhovetski at gmx.de>:
> > Hi Barry
> >
> > On Thu, 11 Apr 2013, Barry Song wrote:
> >
> >> Hi Guennadi,
> >>
> >> > 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.
> >>
> >> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski at xxxxxx>
> >> > ---
> >>
> >> for your patch 1/8 and 3/8, i think it makes a lot of senses to let
> >> the object manages its own clock by itself.
> >> is it possible for us to implement v4l2-clk.c directly as an instance
> >> of standard clk driver for those systems which don't have generic
> >> clock,  and remove the V4L2 clock APIs like v4l2_clk_get,
> >> v4l2_clk_enable from the first day? i mean v4l2-clk.c becomes a temp
> >> and fake clock controller driver. finally, after people have
> >> generically clk, remove it.
> >
> > I don't think you can force-enable the CFF on systems, that don't support
> > it, e.g. PXA.
> 
> yes. we can. clock is only a framework, has it any limitation to
> implement a driver instance on any platform?

So, you enable CFF, it provides its own clk_* implementation like 
clk_get_rate() etc. Now, PXA already has it defined in 
arch/arm/mach-pxa/clock.c. Don't think this is going to fly.

Thanks
Guennadi

> people have tried to move to common clk and generic framework for a
> long time, now you still try to provide a v4l2 specific clock APIs, it
> just makes v4l2 unacceptable and much complex.
> 
> >
> > Thanks
> > Guennadi
> >
> >> > v8: Updated both (C) dates
> >>
> >> >  drivers/media/v4l2-core/Makefile   |    2 +-
> >> >  drivers/media/v4l2-core/v4l2-clk.c |  177 ++++++++++++++++++++++++++++++++++++
> >> >  include/media/v4l2-clk.h           |   54 +++++++++++
> >> >  3 files changed, 232 insertions(+), 1 deletions(-)
> >> >  create mode 100644 drivers/media/v4l2-core/v4l2-clk.c
> >> >  create mode 100644 include/media/v4l2-clk.h
> >>
> >> > diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> >> > index aa50c46..628c630 100644
> >> > --- a/drivers/media/v4l2-core/Makefile
> >> > +++ b/drivers/media/v4l2-core/Makefile
> >> > @@ -5,7 +5,7 @@
> >> >  tuner-objs :=      tuner-core.o
> >>
> >> >  videodev-objs      :=      v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o \
> >> > -                   v4l2-event.o v4l2-ctrls.o v4l2-subdev.o
> >> > +                   v4l2-event.o v4l2-ctrls.o v4l2-subdev.o v4l2-clk.o
> >> > ifeq ($(CONFIG_COMPAT),y)
> >> >    videodev-objs += v4l2-compat-ioctl32.o
> >> >  endif
> >> > diff --git a/drivers/media/v4l2-core/v4l2-clk.c b/drivers/media/v4l2-core/v4l2-clk.c
> >> > new file mode 100644
> >> > index 0000000..d7cc13e
> >> > --- /dev/null
> >> > +++ b/drivers/media/v4l2-core/v4l2-clk.c
> >> > @@ -0,0 +1,177 @@
> >>
> >> -barry
> 
> -barry
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/