Re: [PATCH v4 1/2] drm: Add color management LUT validation helper (v4)

[Matt Roper <matthew.d.roper@intel.com>]

Dave, Daniel - any concerns if we merge this drm core patch through the
Intel tree?  The second patch in the series doesn't apply cleanly in
drm-misc-next.


Matt


On Mon, Dec 17, 2018 at 02:44:14PM -0800, Matt Roper wrote:
> 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: Matt Roper <matthew.d.roper@intel.com>
> Reviewed-by(v1): Brian Starkey <brian.starkey@arm.com>
> Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
> Reviewed-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/drm_color_mgmt.c | 44 ++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_color_mgmt.h     | 29 ++++++++++++++++++++++++++
>  2 files changed, 73 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
> index 07dcf47daafe..968ca7c91ad8 100644
> --- a/drivers/gpu/drm/drm_color_mgmt.c
> +++ b/drivers/gpu/drm/drm_color_mgmt.c
> @@ -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);
> diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h
> index 90ef9996d9a4..6affbda6d9cb 100644
> --- a/include/drm/drm_color_mgmt.h
> +++ b/include/drm/drm_color_mgmt.h
> @@ -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
> -- 
> 2.14.4
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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