drm: Add edid_corrupt flag for Displayport Link CTS 4.2.2.6
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 test never sees the invalid checksum. This results in a failure to pass the compliance test. To correct this issue, when the EDID code detects that the header is invalid, a flag is set to indicate that the EDID is corrupted. In this case, it sets edid_corrupt flag and continues with its fix-up code. This flag is also set in the case of a more seriously damaged header (fixup score less than the threshold). For consistency, the edid_corrupt flag is also set when the checksum is invalid as well. 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 V4: - Removed i915 tag from subject line as the patch is not i915-specific V5: - Moved code causing a compilation error to this patch where the variable is actually declared - Maintained blank lines / spacing so as to not contaminate the patch V6: - Removed extra debug messages - Added documentation to for the added parameter on drm_edid_block_valid - Fixed more whitespace issues in check_link_status - Added a clear of the header_corrupt flag to the end of the test handler in intel_dp.c - Changed the usage of the new function prototype in several places to use NULL where it is not needed by compliance testing V7: - Updated to account for long_pulse flag propagation V8: - Removed clearing of header_corrupt flag from the test handler in intel_dp.c - Added clearing of header_corrupt flag in the drm_edid_block_valid function V9: - Renamed header_corrupt flag to edid_corrupt to more accurately reflect its value and purpose - Updated commit message V10: - Updated for versioning and patch swizzle - Revised the title to more accurately reflect the nature and contents of the patch - Fixed formatting/whitespace problems - Added set flag when computed checksum is invalid Signed-off-by: NTodd Previte <tprevite@gmail.com> Cc: dri-devel@lists.freedesktop.org Acked-by: NDave Airlie <airlied@redhat.com> Reviewed-by: NAlex Deucher <alexander.deucher@amd.com> Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
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