Re: [PATCH 2/4] drm: Create a format/modifier blob

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Jun 23, 2017 at 09:45:42AM -0700, Ben Widawsky wrote:
> Updated blob layout (Rob, Daniel, Kristian, xerpi)
> 
> v2:
> * Removed __packed, and alignment (.+)
> * Fix indent in drm_format_modifier fields (Liviu)
> * Remove duplicated modifier > 64 check (Liviu)
> * Change comment about modifier (Liviu)
> * Remove arguments to blob creation, use plane instead (Liviu)
> * Fix data types (Ben)
> * Make the blob part of uapi (Daniel)
> 
> v3:
> Remove unused ret field.
> Change i, and j to unsigned int (Emil)
> 
> v4:
> Use plane->modifier_count instead of recounting (Daniel)
> 
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Kristian H. Kristensen <hoegsberg@gmail.com>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> Reviewed-by: Daniel Stone <daniels@collabora.com> (v2)
> Reviewed-by: Liviu Dudau <liviu@dudau.co.uk> (v2)
> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> (v3)
> ---
>  drivers/gpu/drm/drm_mode_config.c |  7 ++++
>  drivers/gpu/drm/drm_plane.c       | 83 +++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_mode_config.h     |  6 +++
>  include/uapi/drm/drm_mode.h       | 50 +++++++++++++++++++++++
>  4 files changed, 146 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index d9862259a2a7..6bfbc3839df5 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -337,6 +337,13 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.gamma_lut_size_property = prop;
>  
> +	prop = drm_property_create(dev,
> +				   DRM_MODE_PROP_IMMUTABLE | DRM_MODE_PROP_BLOB,
> +				   "IN_FORMATS", 0);
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.modifiers = prop;
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index d3fc561d7b48..8a2d5765837a 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -62,6 +62,86 @@ static unsigned int drm_num_planes(struct drm_device *dev)
>  	return num;
>  }
>  
> +static inline u32 *
> +formats_ptr(struct drm_format_modifier_blob *blob)
> +{
> +	return (u32 *)(((char *)blob) + blob->formats_offset);
> +}
> +
> +static inline struct drm_format_modifier *
> +modifiers_ptr(struct drm_format_modifier_blob *blob)
> +{
> +	return (struct drm_format_modifier *)(((char *)blob) + blob->modifiers_offset);
> +}
> +
> +static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane)
> +{
> +	const struct drm_mode_config *config = &dev->mode_config;
> +	struct drm_property_blob *blob;
> +	struct drm_format_modifier *mod;
> +	size_t blob_size, formats_size, modifiers_size;
> +	struct drm_format_modifier_blob *blob_data;
> +	unsigned int i, j;
> +
> +	formats_size = sizeof(*plane->format_types) * plane->format_count;

sizeof(__u32) perhaps here since this is about the uabi, not about how
we store the formats internally.

> +	if (WARN_ON(!formats_size)) {
> +		/* 0 formats are never expected */
> +		return 0;
> +	}
> +
> +	modifiers_size =
> +		sizeof(struct drm_format_modifier) * plane->modifier_count;
> +
> +	blob_size = sizeof(struct drm_format_modifier_blob);
> +	/* Modifiers offset is a pointer to a struct with a 64 bit field so it
> +	 * should be naturally aligned to 8B.
> +	 */
> +	blob_size += ALIGN(formats_size, 8);

Here it's ALIGN(format_size) ...

> +	blob_size += modifiers_size;
> +
> +	blob = drm_property_create_blob(dev, blob_size, NULL);
> +	if (IS_ERR(blob))
> +		return -1;
> +
> +	blob_data = (struct drm_format_modifier_blob *)blob->data;
> +	blob_data->version = FORMAT_BLOB_CURRENT;
> +	blob_data->count_formats = plane->format_count;
> +	blob_data->formats_offset = sizeof(struct drm_format_modifier_blob);
> +	blob_data->count_modifiers = plane->modifier_count;
> +
> +	blob_data->modifiers_offset =
> +		ALIGN(blob_data->formats_offset + formats_size, 8);

... but here it's ALIGN(formats_offset+formats_size). I think we should
be aligning the same thing in both cases, or we add a BUILD_BUG_ON to
make sure the header size always stays a multiple of 8 bytes.

That's mainly because the design of the structure seems geared towards
expanding the header in the future (as in why else would you have the
offsets?).

> +
> +	memcpy(formats_ptr(blob_data), plane->format_types, formats_size);
> +
> +	/* If we can't determine support, just bail */
> +	if (!plane->funcs->format_mod_supported)
> +		goto done;
> +
> +	mod = modifiers_ptr(blob_data);
> +	for (i = 0; i < plane->modifier_count; i++) {
> +		for (j = 0; j < plane->format_count; j++) {
> +			if (plane->funcs->format_mod_supported(plane,
> +							       plane->format_types[j],
> +							       plane->modifiers[i])) {
> +
> +				mod->formats |= 1 << j;
> +			}
> +		}
> +
> +		mod->modifier = plane->modifiers[i];
> +		mod->offset = 0;
> +		mod->pad = 0;
> +		mod++;
> +	}
> +
> +done:
> +	drm_object_attach_property(&plane->base, config->modifiers,
> +				   blob->base.id);
> +
> +	return 0;
> +}
> +
>  /**
>   * drm_universal_plane_init - Initialize a new universal plane object
>   * @dev: DRM device
> @@ -181,6 +261,9 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
>  		drm_object_attach_property(&plane->base, config->prop_src_h, 0);
>  	}
>  
> +	if (config->allow_fb_modifiers)
> +		create_in_format_blob(dev, plane);
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_universal_plane_init);
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 42981711189b..03776e659811 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -757,6 +757,12 @@ struct drm_mode_config {
>  	 */
>  	bool allow_fb_modifiers;
>  
> +	/**
> +	 * @modifiers: Plane property to list support modifier/format
> +	 * combination.
> +	 */
> +	struct drm_property *modifiers;

I believe that if we follow the most common naming pattern this should
be "modifiers_property". Also might be good to group it next to the
other properties.

> +
>  	/* cursor size */
>  	uint32_t cursor_width, cursor_height;
>  
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 403339f98a92..a2bb7161f020 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -712,6 +712,56 @@ struct drm_mode_atomic {
>  	__u64 user_data;
>  };
>  
> +struct drm_format_modifier_blob {
> +#define FORMAT_BLOB_CURRENT 1
> +	/* Version of this blob format */
> +	u32 version;
> +
> +	/* Flags */
> +	u32 flags;
> +
> +	/* Number of fourcc formats supported */
> +	u32 count_formats;
> +
> +	/* Where in this blob the formats exist (in bytes) */
> +	u32 formats_offset;
> +
> +	/* Number of drm_format_modifiers */
> +	u32 count_modifiers;
> +
> +	/* Where in this blob the modifiers exist (in bytes) */
> +	u32 modifiers_offset;
> +
> +	/* u32 formats[] */
> +	/* struct drm_format_modifier modifiers[] */
> +};
> +
> +struct drm_format_modifier {
> +	/* Bitmask of formats in get_plane format list this info applies to. The
> +	 * offset allows a sliding window of which 64 formats (bits).
> +	 *
> +	 * Some examples:
> +	 * In today's world with < 65 formats, and formats 0, and 2 are
> +	 * supported
> +	 * 0x0000000000000005
> +	 *		  ^-offset = 0, formats = 5
> +	 *
> +	 * If the number formats grew to 128, and formats 98-102 are
> +	 * supported with the modifier:
> +	 *
> +	 * 0x0000003c00000000 0000000000000000
> +	 *		  ^
> +	 *		  |__offset = 64, formats = 0x3c00000000
> +	 *
> +	 */
> +	__u64 formats;
> +	__u32 offset;
> +	__u32 pad;
> +
> +	/* The modifier that applies to the >get_plane format list bitmask. */
> +	__u64 modifier;
> +};
> +
>  /**
>   * Create a new 'blob' data property, copying length bytes from data pointer,
>   * and returning new blob ID.
> -- 
> 2.13.1
> 
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-- 
Ville Syrjälä
Intel OTC
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