[PATCH 0/3] RFC: Add a drm_aux-dev module.
Ville Syrjälä
ville.syrjala at linux.intel.com
Tue Sep 15 00:35:19 PDT 2015
On Mon, Sep 14, 2015 at 04:12:29PM -0700, Rafael Antognolli wrote:
> 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.
Why would you use ioctls instead of normal read/write syscalls?
>
> 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
>
> --
> 2.4.0
>
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--
Ville Syrjälä
Intel OTC
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