Re: [PATCH 1/2] drm: Add Gamma and Degamma LUT sizes props to drm_crtc to validate.

[Sean Paul <sean@poorly.run>]

On Wed, Sep 29, 2021 at 03:39:25PM -0400, Mark Yacoub wrote:
> From: Mark Yacoub <markyacoub@google.com>
> 
> [Why]
> 1. drm_atomic_helper_check doesn't check for the LUT sizes of either Gamma
> or Degamma props in the new CRTC state, allowing any invalid size to
> be passed on.
> 2. Each driver has its own LUT size, which could also be different for
> legacy users.
> 
> [How]
> 1. Create |degamma_lut_size| and |gamma_lut_size| to save the LUT sizes
> assigned by the driver when it's initializing its color and CTM
> management.
> 2. Create drm_atomic_helper_check_crtc which is called by
> drm_atomic_helper_check to check the LUT sizes saved in drm_crtc that
> they match the sizes in the new CRTC state.
> 

Did you consider extending drm_color_lut_check() with the size checks?

> Fixes: igt@kms_color@pipe-A-invalid-gamma-lut-sizes on MTK
> Tested on Zork(amdgpu) and Jacuzzi(mediatek)
> 
> Signed-off-by: Mark Yacoub<markyacoub@chromium.org>

nit: missing a space between name and email


> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 56 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_color_mgmt.c    |  2 ++
>  include/drm/drm_atomic_helper.h     |  1 +
>  include/drm/drm_crtc.h              | 11 ++++++
>  4 files changed, 70 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 2c0c6ec928200..265b9747250d1 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -930,6 +930,58 @@ drm_atomic_helper_check_planes(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_check_planes);
>  
> +/**
> + * drm_atomic_helper_check_planes - validate state object for CRTC changes

Ctrl+c/Ctrl+v error here

> + * @state: the driver state object
> + *
> + * Check the CRTC state object such as the Gamma/Degamma LUT sizes if the new

Are there missing words between "object" and "such"?

> + * state holds them.
> + *
> + * RETURNS:
> + * Zero for success or -errno
> + */
> +int drm_atomic_helper_check_crtc(struct drm_atomic_state *state)

drm_atomic_helper_check_crtcs to be consistent with
drm_atomic_helper_check_planes

> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *new_crtc_state;
> +	int i;
> +
> +	for_each_new_crtc_in_state (state, crtc, new_crtc_state, i) {

no space before (

> +		if (new_crtc_state->gamma_lut) {

Perhaps gate these with a check of state->color_mgmt_changed first?

> +			uint64_t supported_lut_size = crtc->gamma_lut_size;
> +			uint32_t supported_legacy_lut_size = crtc->gamma_size;
> +			uint32_t new_state_lut_size =
> +				drm_color_lut_size(new_crtc_state->gamma_lut);

nit: new_state_lut_size and supported_lut_size can be pulled out to top level scope
to avoid re-instantiation on each iteration

> +
> +			if (new_state_lut_size != supported_lut_size &&
> +			    new_state_lut_size != supported_legacy_lut_size) {

According to the docbook, "If drivers support multiple LUT sizes then they
should publish the largest size, and sub-sample smaller sized LUTs". So
should this check be > instead of != ?

> +				DRM_DEBUG_DRIVER(

drm_dbg_state() is probably more appropriate

> +					"Invalid Gamma LUT size. Should be %u (or %u for legacy) but got %u.\n",
> +					supported_lut_size,
> +					supported_legacy_lut_size,
> +					new_state_lut_size);
> +				return -EINVAL;
> +			}
> +		}
> +
> +		if (new_crtc_state->degamma_lut) {
> +			uint32_t new_state_lut_size =
> +				drm_color_lut_size(new_crtc_state->degamma_lut);
> +			uint64_t supported_lut_size = crtc->degamma_lut_size;
> +
> +			if (new_state_lut_size != supported_lut_size) {
> +				DRM_DEBUG_DRIVER(

drm_dbg_state()

> +					"Invalid Degamma LUT size. Should be %u but got %u.\n",
> +					supported_lut_size, new_state_lut_size);
> +				return -EINVAL;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_check_crtc);
> +
>  /**
>   * drm_atomic_helper_check - validate state object
>   * @dev: DRM device
> @@ -975,6 +1027,10 @@ int drm_atomic_helper_check(struct drm_device *dev,
>  	if (ret)
>  		return ret;
>  
> +	ret = drm_atomic_helper_check_crtc(state);
> +	if (ret)
> +		return ret;
> +
>  	if (state->legacy_cursor_update)
>  		state->async_update = !drm_atomic_helper_async_check(dev, state);
>  
> diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
> index bb14f488c8f6c..72a1b628e7cdd 100644
> --- a/drivers/gpu/drm/drm_color_mgmt.c
> +++ b/drivers/gpu/drm/drm_color_mgmt.c
> @@ -166,6 +166,7 @@ void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
>  	struct drm_mode_config *config = &dev->mode_config;
>  
>  	if (degamma_lut_size) {
> +		crtc->degamma_lut_size = degamma_lut_size;
>  		drm_object_attach_property(&crtc->base,
>  					   config->degamma_lut_property, 0);
>  		drm_object_attach_property(&crtc->base,
> @@ -178,6 +179,7 @@ void drm_crtc_enable_color_mgmt(struct drm_crtc *crtc,
>  					   config->ctm_property, 0);
>  
>  	if (gamma_lut_size) {
> +		crtc->gamma_lut_size = gamma_lut_size;
>  		drm_object_attach_property(&crtc->base,
>  					   config->gamma_lut_property, 0);
>  		drm_object_attach_property(&crtc->base,
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index 4045e2507e11c..3eda13622ca1e 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -38,6 +38,7 @@ struct drm_atomic_state;
>  struct drm_private_obj;
>  struct drm_private_state;
>  
> +int drm_atomic_helper_check_crtc(struct drm_atomic_state *state);
>  int drm_atomic_helper_check_modeset(struct drm_device *dev,
>  				struct drm_atomic_state *state);
>  int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 13eeba2a750af..c602be2cafca9 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1072,6 +1072,17 @@ struct drm_crtc {
>  	/** @funcs: CRTC control functions */
>  	const struct drm_crtc_funcs *funcs;
>  
> +	/**
> +	 * @degamma_lut_size: Size of degamma LUT.
> +	 */
> +	uint32_t degamma_lut_size;
> +
> +	/**
> +	 * @gamma_lut_size: Size of Gamma LUT. Not used by legacy userspace such as
> +	 * X, which doesn't support large lut sizes.
> +	 */
> +	uint32_t gamma_lut_size;
> +

Above, you're checking 

if (new_state_lut_size != gamma_size && new_state_lut_size != gamma_lut_size)
        fail;

doesn't that imply that gamma_size and gamma_lut_size must always be equal? If
so, perhaps turf this new state and rename degamma_lut_size to degamma_size to
be consistent.

De-duping this and initializing crtc->gamma_size in the initialization would
mean the if (crtc->gamma_size) check in drm_crtc_supports_legacy_check() is no
longer useful (and possibly other similar checks), so some care will need to be
taken to avoid regression. I think the effort is worthwhile to avoid introducing
new state.



>  	/**
>  	 * @gamma_size: Size of legacy gamma ramp reported to userspace. Set up
>  	 * by calling drm_mode_crtc_set_gamma_size().
> -- 
> 2.33.0.685.g46640cef36-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS

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