[v2,1/2] drm: Add color management LUT validation helper (v2)

Commit Message

Matt Roper Dec. 13, 2018, 9:55 p.m. UTC

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)

Cc: Uma Shankar <[e-mail]>
Cc: Swati Sharma <[e-mail]>
Cc: Brian Starkey <[e-mail]>
Signed-off-by: Matt Roper <[e-mail]>
Reviewed-by(v1): Brian Starkey <[e-mail]>
---
 drivers/gpu/drm/drm_color_mgmt.c | 64 ++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_color_mgmt.h     |  5 ++++
 2 files changed, 69 insertions(+)

Comments

Alexandru-Cosmin Gheorghe Dec. 14, 2018, 9:43 a.m. UTC | #1

Hi,

On Thu, Dec 13, 2018 at 01:55:25PM -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)
> 
> Cc: Uma Shankar <[e-mail]>
> Cc: Swati Sharma <[e-mail]>
> Cc: Brian Starkey <[e-mail]>
> Signed-off-by: Matt Roper <[e-mail]>
> Reviewed-by(v1): Brian Starkey <[e-mail]>
> ---
>  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;
> +	}
> +

Isn't this already covered by drm_atomic_replace_property_blob_from_id ?
Other than that feel free to add:

Reviewed-by: Alexandru Gheorghe <[e-mail]>

> +	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
> 
> _______________________________________________
> dri-devel mailing list
> [e-mail]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Shankar, Uma Dec. 14, 2018, 2:26 p.m. UTC | #2

>-----Original Message-----
>From: Roper, Matthew D
>Sent: Friday, December 14, 2018 3:25 AM
>To: [e-mail]; [e-mail]
>Cc: Roper, Matthew D <[e-mail]>; Shankar, Uma
><[e-mail]>; Sharma, Swati2 <[e-mail]>; Brian
>Starkey <[e-mail]>
>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 <[e-mail]>

>Cc: Uma Shankar <[e-mail]>
>Cc: Swati Sharma <[e-mail]>
>Cc: Brian Starkey <[e-mail]>
>Signed-off-by: Matt Roper <[e-mail]>
>Reviewed-by(v1): Brian Starkey <[e-mail]>
>---
> 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

Matt Roper Dec. 14, 2018, 6:24 p.m. UTC | #3

On Fri, Dec 14, 2018 at 09:43:08AM +0000, Alexandru-Cosmin Gheorghe wrote:
...
> > +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;
> > +	}
> > +
> 
> Isn't this already covered by drm_atomic_replace_property_blob_from_id ?
> Other than that feel free to add:
> 
> Reviewed-by: Alexandru Gheorghe <[e-mail]>

Ah, you're right.  I thought there was a test somewhere but couldn't
find where we did it when I looked earlier.  I'll drop this extra test;
thanks for pointing that out.


Matt

> 
> > +	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
> > 
> > _______________________________________________
> > dri-devel mailing list
> > [e-mail]
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Cheers,
> Alex G

Daniel Vetter Dec. 17, 2018, 9:49 a.m. UTC | #4

On Thu, Dec 13, 2018 at 01:55:25PM -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)
> 
> Cc: Uma Shankar <[e-mail]>
> Cc: Swati Sharma <[e-mail]>
> Cc: Brian Starkey <[e-mail]>
> Signed-off-by: Matt Roper <[e-mail]>
> Reviewed-by(v1): Brian Starkey <[e-mail]>
> ---
>  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).

For internal stuff an enum would be much better (you can still do
bitmasks), that also gives you a nice way to document the enum values
using kerneldoc. With enums you can then document them like a struct,
using inline comments.

This style here we only use for properties, which are real strings (hence
the "", for C constants/defines that looks funny).

Cheers, Daniel

> + *
> + * 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
> 
> _______________________________________________
> Intel-gfx mailing list
> [e-mail]
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Ville Syrjälä Dec. 17, 2018, 1:55 p.m. UTC | #5

On Thu, Dec 13, 2018 at 01:55:25PM -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)
> 
> Cc: Uma Shankar <[e-mail]>
> Cc: Swati Sharma <[e-mail]>
> Cc: Brian Starkey <[e-mail]>
> Signed-off-by: Matt Roper <[e-mail]>
> Reviewed-by(v1): Brian Starkey <[e-mail]>
> ---
>  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).

DRM_COLOR_LUT_NON_DECREASING?

Or DRM_COLOR_LUT_MONOTONICALLY_INCREASING, but that's getting
a bit long :)

> + *
> + * 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
> 
> _______________________________________________
> dri-devel mailing list
> [e-mail]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Brian Starkey Dec. 21, 2018, 12:50 p.m. UTC | #6

Hi Matt,

On Thu, Dec 13, 2018 at 01:55:25PM -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)

nit: Technically we're 'Arm' now

> 
> Cc: Uma Shankar <[e-mail]>
> Cc: Swati Sharma <[e-mail]>
> Cc: Brian Starkey <[e-mail]>
> Signed-off-by: Matt Roper <[e-mail]>
> Reviewed-by(v1): Brian Starkey <[e-mail]>

Looks good to me, feel free to drop the (v1) qualifier. Thanks again!

-Brian

> ---
>  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
>

Patch

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