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

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jan 11, 2019 at 02:27:00PM -0800, Matt Roper wrote:
> 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.

Hm, need to discuss with Dave how good my ack powers are now. In the past
we had the rule that I asked him for an explicit ack, but back then I was
still maintainer of i915, so a bit a too obvious conflict there. I think
with the separate roles me acking should be good enough.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Dave, sounds reasonable?
-Daniel

> 
> 
> 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

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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