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Commit 3c8861d8 authored by Matt Roper's avatar Matt Roper
Browse files

drm: Add color management LUT validation helper (v4) 



Some hardware may place additional restrictions on the gamma/degamma
curves described by our LUT properties.  E.g., that a gamma curve never
decreases or that the red/green/blue channels of a LUT's entries must be
equal.  Let's add a helper function that drivers can use to test that a
userspace-provided LUT is valid and doesn't violate hardware
requirements.

v2:
 - Combine into a single helper that just takes a bitmask of the tests
   to apply.  (Brian Starkey)
 - Add additional check (always performed) that LUT property blob size
   is always a multiple of the LUT entry size.  (stolen from ARM driver)

v3:
 - Drop the LUT size check again since
   drm_atomic_replace_property_blob_from_id() already covers this for
   us.  (Alexandru Gheorghe)

v4:
 - Use an enum to describe possible test values rather than #define's;
   this is cleaner to provide kerneldoc for.  (Daniel Vetter)
 - s/DRM_COLOR_LUT_INCREASING/DRM_COLOR_LUT_NON_DECREASING/.  (Ville)

Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Swati Sharma <swati2.sharma@intel.com>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: default avatarBrian Starkey <brian.starkey@arm.com>
Reviewed-by: default avatarAlexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Reviewed-by: default avatarUma Shankar <uma.shankar@intel.com>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181217224415.12848-1-matthew.d.roper@intel.com
parent 6e062b60

drivers/gpu/drm/drm_color_mgmt.c

+44 −0
Original line number Diff line number Diff line
@@ -462,3 +462,47 @@ int drm_plane_create_color_properties(struct drm_plane *plane, 
	return 0;

}

EXPORT_SYMBOL(drm_plane_create_color_properties);



/**

 * drm_color_lut_check - check validity of lookup table

 * @lut: property blob containing LUT to check

 * @tests: bitmask of tests to run

 *

 * Helper to check whether a userspace-provided lookup table is valid and

 * satisfies hardware requirements.  Drivers pass a bitmask indicating which of

 * the tests in &drm_color_lut_tests should be performed.

 *

 * Returns 0 on success, -EINVAL on failure.

 */

int drm_color_lut_check(struct drm_property_blob *lut,

			uint32_t tests)

{

	struct drm_color_lut *entry;

	int i;



	if (!lut || !tests)

		return 0;



	entry = lut->data;

	for (i = 0; i < drm_color_lut_size(lut); i++) {

		if (tests & DRM_COLOR_LUT_EQUAL_CHANNELS) {

			if (entry[i].red != entry[i].blue ||

			    entry[i].red != entry[i].green) {

				DRM_DEBUG_KMS("All LUT entries must have equal r/g/b\n");

				return -EINVAL;

			}

		}



		if (i > 0 && tests & DRM_COLOR_LUT_NON_DECREASING) {

			if (entry[i].red < entry[i - 1].red ||

			    entry[i].green < entry[i - 1].green ||

			    entry[i].blue < entry[i - 1].blue) {

				DRM_DEBUG_KMS("LUT entries must never decrease.\n");

				return -EINVAL;

			}

		}

	}



	return 0;

}

EXPORT_SYMBOL(drm_color_lut_check);

include/drm/drm_color_mgmt.h

+29 −0
Original line number Diff line number Diff line
@@ -69,4 +69,33 @@ int drm_plane_create_color_properties(struct drm_plane *plane, 
				      u32 supported_ranges,

				      enum drm_color_encoding default_encoding,

				      enum drm_color_range default_range);



/**

 * enum drm_color_lut_tests - hw-specific LUT tests to perform

 *

 * The drm_color_lut_check() function takes a bitmask of the values here to

 * determine which tests to apply to a userspace-provided LUT.

 */

enum drm_color_lut_tests {

	/**

	 * @DRM_COLOR_LUT_EQUAL_CHANNELS:

	 *

	 * Checks whether the entries of a LUT all have equal values for the

	 * red, green, and blue channels.  Intended for hardware that only

	 * accepts a single value per LUT entry and assumes that value applies

	 * to all three color components.

	 */

	DRM_COLOR_LUT_EQUAL_CHANNELS = BIT(0),



	/**

	 * @DRM_COLOR_LUT_NON_DECREASING:

	 *

	 * Checks whether the entries of a LUT are always flat or increasing

	 * (never decreasing).

	 */

	DRM_COLOR_LUT_NON_DECREASING = BIT(1),

};



int drm_color_lut_check(struct drm_property_blob *lut,

			uint32_t tests);

#endif