[PATCH 0/3] RFC: Add a drm_aux-dev module.

[Rafael Antognolli]

This is a tentative implementation of a module that allows reading/writing
arbitrary dpcd registers, following the suggestion from Daniel Vetter. It
assumes the drm aux helpers were used by the driver.

I tried to follow the i2c-dev implementation as close as possible, but the only
operations that are provided on the dev node are two different ioctl's, one for
reading a register and another one for writing it.

I have at least 2 open questions:

 * Right now the AUX channels are stored in a global list inside the
   drm_dp_helper implementation, and I assume that's not ideal. A different
   approach would be to iterate over the list of connectors, instead of the
   list of AUX channels, but that would require the struct drm_connector or
   similar to know about the respective aux helper. It could be added as a
   function to register that, or as a new method on the drm_connector_funcs to
   retrieve the aux channel helper.

 * From the created sysfs drm_aux-dev device it's possible to know what is the
   respective connector, but not the other way around. Is this good enough?

Please provide any feedback you have and tell me if this is the idea you had
initially for this kind of implementation. Or, if it's nothing like this, let
me know what else you had in mind.

If I'm going in the right direction, I'll refine the patch to provide full
documentation and tests if needed.

Rafael Antognolli (3):
  drm/dp: Keep a list of drm_dp_aux helper.
  drm/dp: Store the drm_connector device pointer on the helper.
  drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

 Documentation/ioctl/ioctl-number.txt |   1 +
 drivers/gpu/drm/Kconfig              |   4 +
 drivers/gpu/drm/Makefile             |   1 +
 drivers/gpu/drm/drm_aux-dev.c        | 390 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_dp_helper.c      |  71 +++++++
 drivers/gpu/drm/i915/intel_dp.c      |   1 +
 include/drm/drm_dp_helper.h          |   7 +
 include/uapi/linux/Kbuild            |   1 +
 include/uapi/linux/drm_aux-dev.h     |  45 ++++
 9 files changed, 521 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_aux-dev.c
 create mode 100644 include/uapi/linux/drm_aux-dev.h

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2.4.0