>-----Original Message-----
>From: Roper, Matthew D
>Sent: Friday, December 14, 2018 3:25 AM
>To: dri-devel@xxxxxxxxxxxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
>Cc: Roper, Matthew D <matthew.d.roper@xxxxxxxxx>; Shankar, Uma
><uma.shankar@xxxxxxxxx>; Sharma, Swati2 <swati2.sharma@xxxxxxxxx>; Brian
>Starkey <Brian.Starkey@xxxxxxx>
>Subject: [PATCH v2 1/2] drm: Add color management LUT validation helper (v2)
>
>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)
Looks ok to me.
Reviewed-By: Uma Shankar <uma.shankar@xxxxxxxxx>
>Cc: Uma Shankar <uma.shankar@xxxxxxxxx>
>Cc: Swati Sharma <swati2.sharma@xxxxxxxxx>
>Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
>Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
>Reviewed-by(v1): Brian Starkey <brian.starkey@xxxxxxx>
>---
> drivers/gpu/drm/drm_color_mgmt.c | 64
>++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_color_mgmt.h | 5 ++++
> 2 files changed, 69 insertions(+)
>
>diff --git a/drivers/gpu/drm/drm_color_mgmt.c
>b/drivers/gpu/drm/drm_color_mgmt.c
>index 07dcf47daafe..5c2a2d228412 100644
>--- a/drivers/gpu/drm/drm_color_mgmt.c
>+++ b/drivers/gpu/drm/drm_color_mgmt.c
>@@ -462,3 +462,67 @@ 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 additional hardware requirements. All table sizes should
>+be a
>+ * multiple of sizeof(struct drm_color_lut). Drivers pass a bitmask
>+indicating
>+ * which of the following additional tests should also be performed:
>+ *
>+ * "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_INCREASING":
>+ * Checks whether the entries of a LUT are always flat or increasing
>+ * (never decreasing).
>+ *
>+ * 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)
>+ return 0;
>+
>+ if (lut->length % sizeof(struct drm_color_lut)) {
>+ DRM_DEBUG_KMS("LUT size (%lu) is not a multiple of LUT entry
>size (%lu)\n",
>+ lut->length, sizeof(struct drm_color_lut));
>+ return -EINVAL;
>+ }
>+
>+ if (!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_INCREASING) {
>+ 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..7de16f70bcc3 100644
>--- a/include/drm/drm_color_mgmt.h
>+++ b/include/drm/drm_color_mgmt.h
>@@ -69,4 +69,9 @@ 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);
>+
>+#define DRM_COLOR_LUT_EQUAL_CHANNELS BIT(0)
>+#define DRM_COLOR_LUT_INCREASING BIT(1)
>+int drm_color_lut_check(struct drm_property_blob *lut,
>+ uint32_t tests);
> #endif
>--
>2.14.4
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