Re: [PATCH v3 1/4] drm: Add drm_any_plane_has_format()

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Fri, 2018-03-09 at 17:14 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Add a function to check whether there is at least one plane that
> supports a specific format and modifier combination. Drivers can
> use this to reject unsupported formats/modifiers in .fb_create().
> 
> v2: Accept anyformat if the driver doesn't do planes (Eric)
>     s/planes_have_format/any_plane_has_format/ (Eric)
>     Check the modifier as well since we already have a function
>     that does both
> v3: Don't do the check in the core since we may not know the
>     modifier yet, instead export the function and let drivers
>     call it themselves
> 
> Cc: Eric Anholt <eric@anholt.net>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

I ended up writing a similar patch for i915. Having this in the core
seems better and patch still applies cleanly.

Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>

> ---
>  drivers/gpu/drm/drm_plane.c   | 23 +++++++++++++++++++++++
>  include/drm/drm_mode_config.h |  6 ++++++
>  include/drm/drm_plane.h       |  2 ++
>  3 files changed, 31 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c
> b/drivers/gpu/drm/drm_plane.c
> index a5d1fc7e8a37..3b2d6f8d889d 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -578,6 +578,29 @@ int drm_plane_check_pixel_format(struct
> drm_plane *plane,
>  	return 0;
>  }
>  
> +/**
> + * drm_any_plane_has_format - Check whether any plane supports this
> format and modifier combination
> + * @dev: DRM device
> + * @format: pixel format (DRM_FORMAT_*)
> + * @modifier: data layout modifier
> + *
> + * Returns:
> + * Whether at least one plane supports the specified format and
> modifier combination.
> + */
> +bool drm_any_plane_has_format(struct drm_device *dev,
> +			      u32 format, u64 modifier)
> +{
> +	struct drm_plane *plane;
> +
> +	drm_for_each_plane(plane, dev) {
> +		if (drm_plane_check_pixel_format(plane, format,
> modifier) == 0)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(drm_any_plane_has_format);
> +
>  /*
>   * __setplane_internal - setplane handler for internal callers
>   *
> diff --git a/include/drm/drm_mode_config.h
> b/include/drm/drm_mode_config.h
> index 7569f22ffef6..9b894de9a75d 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -52,6 +52,12 @@ struct drm_mode_config_funcs {
>  	 * requested metadata, but most of that is left to the driver.
> See
>  	 * &struct drm_mode_fb_cmd2 for details.
>  	 *
> +	 * To validate the pixel format and modifier drivers can use
> +	 * drm_any_plane_has_format() to make sure at least one plane
> supports
> +	 * the requested values. Note that the driver must first
> determine the
> +	 * actual modifier used if the request doesn't have it
> specified,
> +	 * ie. when (@mode_cmd->flags & DRM_MODE_FB_MODIFIERS) == 0.
> +	 *
>  	 * If the parameters are deemed valid and the backing storage
> objects in
>  	 * the underlying memory manager all exist, then the driver
> allocates
>  	 * a new &drm_framebuffer structure, subclassed to contain
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index f7bf4a48b1c3..930e8fdd90f8 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -683,5 +683,7 @@ static inline struct drm_plane
> *drm_plane_find(struct drm_device *dev,
>  #define drm_for_each_plane(plane, dev) \
>  	list_for_each_entry(plane, &(dev)->mode_config.plane_list,
> head)
>  
> +bool drm_any_plane_has_format(struct drm_device *dev,
> +			      u32 format, u64 modifier);
>  
>  #endif

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