[RFC] Move some soc-camera drivers to staging in preparation for removal

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi all,

The soc-camera framework is a problem for reusability of sub-device drivers since
those need access to the soc-camera framework. Which defeats the purpose of the
sub-device framework. It is the reason why we still have a media/i2c/soc-camera
directory for subdevs that can only work with soc-camera.

Ideally I would like to drop soc-camera completely, but it is still in use.

One of the largest users is Renesas with their r-car SoC, but Niklas Söderlund
made a replacement driver that should make it possible to remove the soc-camera
r-car driver, hopefully this year.

What I would like to do is to move soc-camera drivers that we consider obsolete
to staging, and remove them in 1-2 kernel cycles if nobody steps up.

See also this past thread from Guennadi:

http://www.spinics.net/lists/linux-media/msg89253.html

And yes, I said in that thread that I was OK with keeping soc-camera as-is. But
it still happens that companies pick this framework for new devices (the driver
for the Tegra K1 for example). It is another reason besides the reusability issue
for remove this framework more aggressively then I intended originally.


We have the following drivers:

- pxa_camera for the PXA27x Quick Capture Interface

  Apparently this architecture still gets attention (see the link to the thread
  above). But it does use vb1 which we really want to phase out soon. Does anyone
  know if this driver still works with the latest kernel? Because it is using vb1
  it is a strong candidate for removing it (or replacing it with something better
  if someone steps up).

- mx2_camera: i.MX27 Camera Sensor Interface

  Have not seen any development since April 2013 (mx2-camera: move interface
  activation and deactivation to clock callbacks by Guennadi). No idea if it still
  works or if it is still in use. Does anyone know?

- mx3_camera: i.MX3x Camera Sensor Interface

  Have not seen any development since July 2013 (add support for asynchronous
  subdevice registration by Guennadi). Same as for mx2_camera: does it still work?
  Is it still in use?

- omap1_camera: OMAP1 Camera Interface

  It uses vb1, so that's one very good reason for removing it. And as far as I
  know it is unused and likely won't work.

- sh_mobile_ceu_camera: SuperH Mobile CEU Interface

  I worked on this, but I know it does function anymore. I'd say that this can
  be removed.

- sh_mobile_csi2: SuperH Mobile MIPI CSI-2 Interface

  I don't have hardware to test, but I'd be surprised if it still works. Can
  someone test? If it is broken, then it can be moved to staging.

- rcar_vin: R-Car Video Input (VIN)
  Will be replaced with a regular driver as mentioned above.

- atmel-isi: ATMEL Image Sensor Interface (ISI)

  I believe this is still actively maintained. Would someone be willing to
  convert this? It doesn't look like a complex driver.

Now I am not planning to remove soc-camera (yet), but at least we should get
rid of unmaintained drivers, especially if they don't work anymore or if they
use the old vb1 mess.

And we can then take a good look at what remains.

Regards,

	Hans