On Monday 22 February 2010 17:01:39 Rodolfo Giometti wrote:
> On Fri, Feb 19, 2010 at 08:36:38PM +0100, Guennadi Liakhovetski wrote:
> > On Fri, 19 Feb 2010, Rodolfo Giometti wrote:
> >
> > > Hello,
> > >
> > > on my pxa27x based board I have a adv7180 connected with the CIF
> > > interface. Due this fact I'm going to use the pxa_camera.c driver
> > > which in turn registers a soc_camera_host.
> > >
> > > In the latest kernel I found your driver for the ADV7180, but it
> > > registers the chip as a v4l sub device.
> > >
> > > I suppose these two interfaces are not compatible, aren't they?
> >
> > Congratulations! Thereby you're in a position to develop the first
> > v4l2-subdev / soc-camera universal driver;) The answer to this your
> > question is - they are... kinda. This means - yes, soc-camera is also
> > using the v4l2-subdev API, but - with a couple of additions. Basically,
> > there are two things you have to change in the adv7180 driver to make it
> > compatible with soc-camera - (1) add bus-configuration methods, even if
> > they don't do much (see .query_bus_param() and .set_bus_param() methods
> > from struct soc_camera_ops), and (2) migrate the driver to the mediabus
> > API. The latter one requires some care - in principle, mediabus should be
> > the future API to negotiate parameters on the video bus between bridges
> > (in your case PXA CIF) and clients, but for you this means you also have
> > to migrate any other bridge drivers in the mainline to that API, and, if
> > they also interface to some other subdevices - those too, and if those can
> > also work with other bridges - those too...;) But, I think, that chain
> > will terminate quite soon, in fact, I cannot find any users of that driver
> > currently in the mainline, Richard?
> >
> > > In this situation, should I write a new driver for the
> > > soc_camera_device? Which is The-Right-Thing(TM) to do? :)
> >
> > Please, have a look and try to convert the driver as described above. All
> > the APIs and a few examples are in the mainline, so, you should have
> > enough copy-paste sources;) Ask on the list (with me on cc) if anything is
> > still unclear.
>
> Thanks for your quick answer! :)
>
> What I still don't understand is if should I move the driver form
> v4l2-subdev to a soc_camera device or trying to support both API...
>
> It seems to me that the driver is not used by any machines into
> mainline so if soc-camera is also using the v4l2-subdev API but with a
> couple of additions I suppose I can move it to soc_camera API...
The long-term goal is to remove the last soc-camera API dependencies from
the sensor subdev drivers. Subdevice (usually i2c) drivers should be fully
reusable and a dependency on soc-camera defeats that goal.
I think the only missing piece is low-level bus setup (i.e. sync polarities,
rising/falling edge sampling, etc.). Some proposals were made, but basically
nobody has had the time to actually implement this.
Right now, if you want to use your sensor with soc-camera, then you need to
support the soc-camera API (or what is left of it) in your subdev driver as
well.
Regards,
Hans
>
> Is that right?
>
> Ciao,
>
> Rodolfo
>
>
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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