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

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
......@@ -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);
......@@ -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
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