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

[Barry Song]

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?
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