[PATCH 06/11] drm/i915: Add supporting structure for Displayport Link CTS test 4.2.2.6

[Todd Previte]

Easy enough to do. Tag removed and updated patch posted. Thanks Emil!

On 4/10/2015 10:45 AM, Emil Velikov wrote:
> Hi Todd
>
> On 10/04/15 16:12, Todd Previte wrote:
>> Displayport compliance test 4.2.2.6 requires that a source device be capable of
>> detecting a corrupt EDID. The test specification states that the sink device
>> sets up the EDID with an invalid checksum. To do this, the sink sets up an
>> invalid EDID header, expecting the source device to generate the checksum and
>> compare it to the value stored in the last byte of the block data.
>>
>> Unfortunately, the DRM EDID reading and parsing functions are actually too good
>> in this case; the header is fixed before the checksum is computed and thus the
>> code never sees the invalid checksum. This results in a failure to pass the
>> compliance test.
>>
>> To correct this issue, a checksum is generated when the EDID header is detected
>> as corrupted. If the checksum is invalid, it sets the header_corrupt flag and
>> logs the errors. In the case of a more seriously damaged header (fixup score
>> less than the threshold) the code does not generate the checksum but does set
>> the header_corrupt flag.
>>
>> V2:
>> - Removed the static bool global
>> - Added a bool to the drm_connector struct to reaplce the static one for
>>    holding the status of raw edid header corruption detection
>> - Modified the function signature of the is_valid function to take an
>>    additional parameter to store the corruption detected value
>> - Fixed the other callers of the above is_valid function
>> V3:
>> - Updated the commit message to be more clear about what and why this
>>    patch does what it does.
>> - Added comment in code to clarify the operations there
>> - Removed compliance variable and check_link_status update; those
>>    have been moved to a later patch
>> - Removed variable assignment from the bottom of the test handler
>>
>> Signed-off-by: Todd Previte <tprevite at gmail.com>
>> Cc: dri-devel at lists.freedesktop.org
>> ---
>>   drivers/gpu/drm/drm_edid.c        | 31 ++++++++++++++++++++++++++-----
>>   drivers/gpu/drm/drm_edid_load.c   |  7 +++++--
>>   drivers/gpu/drm/i2c/tda998x_drv.c |  4 ++--
>>   include/drm/drm_crtc.h            |  8 +++++++-
>>   4 files changed, 40 insertions(+), 10 deletions(-)
>>
> Neither this nor patch 09/11 seems to be i915 specific. If you're doing
> another revision you might want to use just "drm:".
>
> Cheers,
> Emil