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

[Barry Song]

2013/4/11 Guennadi Liakhovetski <g.liakhovetski at gmx.de>:
> 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.

agree.

>
> 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