[PATCH v8 0/10] Output raw touch data via V4L2

[Nick Dyer <nick@shmanahar.org>]

This is a series of patches to add output of raw touch diagnostic data via V4L2
to the Atmel maXTouch and Synaptics RMI4 drivers.

It's a rewrite of the previous implementation which output via debugfs: it now
uses a V4L2 device in a similar way to the sur40 driver.

We have a utility which can read the data and display it in a useful format:
    https://github.com/ndyer/heatmap/commits/heatmap-v4l

Changes in v8:
- Split out docs changes, rework in RST/Sphinx, and rebase against docs-next
- Update for changes to vb2_queue alloc_ctxs
- Rebase against git://linuxtv.org/media_tree.git and re-test

Changes in v7:
- Tested by Andrew Duggan and Chris Healy.
- Update bus_info to add "rmi4:" bus.
- Fix code style issues in sur40 changes.

Changes in v6:
- Remove BUF_TYPE_TOUCH_CAPTURE, as discussed with Hans V touch devices will
  use BUF_TYPE_VIDEO_CAPTURE.
- Touch devices should now register CAP_VIDEO_CAPTURE: CAP_TOUCH just says that
  this is a touch device, not a video device, but otherwise it acts the same.
- Add some code to v4l_s_fmt() to set sensible default values for fields not
  used by touch.
- Improve naming/doc of RMI4 F54 report types.
- Various minor DocBook fixes, and split to separate patch.
- Update my email address.
- Rework sur40 changes so that PIX_FMT_GREY is supported for backward
  compatibility. Florian is it possible for you to test?

Changes in v5 (Hans Verkuil review):
- Update v4l2-core:
  - Add VFL_TYPE_TOUCH, V4L2_BUF_TYPE_TOUCH_CAPTURE and V4L2_CAP_TOUCH
  - Change V4L2_INPUT_TYPE_TOUCH_SENSOR to V4L2_INPUT_TYPE_TOUCH
  - Improve DocBook documentation
  - Add FMT definitions for touch data
  - Note this will need the latest version of the heatmap util
- Synaptics RMI4 driver:
  - Remove some less important non full frame report types
  - Switch report type names to const char * array
  - Move a static array to inside context struct
- Split sur40 changes to a separate commit

Changes in v4:
- Address nits from the input side in atmel_mxt_ts patches (Dmitry Torokhov)
- Add Synaptics RMI4 F54 support patch

Changes in v3:
- Address V4L2 review comments from Hans Verkuil
- Run v4l-compliance and fix all issues - needs minor patch here:
  https://github.com/ndyer/v4l-utils/commit/cf50469773f

Changes in v2:
- Split pixfmt changes into separate commit and add DocBook
- Introduce VFL_TYPE_TOUCH_SENSOR and /dev/v4l-touch
- Remove "single node" support for now, it may be better to treat it as
  metadata later
- Explicitly set VFL_DIR_RX
- Fix Kconfig