[PATCH v3 0/8] Input: atmel_mxt_ts - output raw touch diagnostic data via V4L

This is a series of patches to add diagnostic data support to the Atmel
maXTouch driver. 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.

There are significant performance advantages to putting this code into the
driver.  The algorithm for retrieving the data has been fairly consistent
across a range of chips, with the exception of the mXT1386 series (see patch).

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

These patches are also available from
    https://github.com/ndyer/linux/commits/diagnostic-v4l

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