[Intel-gfx] [PATCH v2 2/3] drm: Create a format/modifier blob

[Emil Velikov]

Hi Ben,

On 16 May 2017 at 22:31, Ben Widawsky <ben at bwidawsk.net> 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)
>
> Cc: Rob Clark <robdclark at gmail.com>
> Cc: Daniel Stone <daniels at collabora.com>
> Cc: Kristian H. Kristensen <hoegsberg at gmail.com>
> Cc: Liviu Dudau <liviu at dudau.co.uk>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> Reviewed-by: Daniel Stone <daniels at collabora.com>

I think this is almost perfect, barring the UAPI nitpick.
The rest is somewhat of a bikeshedding.

With the UAPI resolved, regardless of the rest
Reviewed-by: Emil Velikov <emil.l.velikov at gmail.com>


> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c

> +static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane)
> +{
> +       const struct drm_mode_config *config = &dev->mode_config;
> +       const uint64_t *temp_modifiers = plane->modifiers;
> +       unsigned int format_modifier_count = 0;
> +       struct drm_property_blob *blob = NULL;
> +       struct drm_format_modifier *mod;
> +       size_t blob_size = 0, formats_size, modifiers_size;
There's no need to initialize blob and blob_size here.

> +       struct drm_format_modifier_blob *blob_data;
> +       int i, j, ret = 0;
Make i and j unsigned to match format_modifier_count and
plane->format_count respectively.
Then expand ret in the only place where it's used?

> +
> +       if (plane->modifiers)
> +               while (*temp_modifiers++ != DRM_FORMAT_MOD_INVALID)
> +                       format_modifier_count++;
> +
> +       formats_size = sizeof(*plane->format_types) * plane->format_count;
> +       if (WARN_ON(!formats_size)) {
> +               /* 0 formats are never expected */
> +               return 0;
> +       }
> +
> +       modifiers_size =
> +               sizeof(struct drm_format_modifier) * format_modifier_count;
> +
> +       blob_size = sizeof(struct drm_format_modifier_blob);
> +       blob_size += ALIGN(formats_size, 8);
Worth having the "Modifiers offset is a pointer..." comment moved/copied here?

> +       blob_size += modifiers_size;
> +
> +       blob = drm_property_create_blob(dev, blob_size, NULL);
> +       if (IS_ERR(blob))
> +               return -1;
> +
Maybe propagate the exact error... Hmm we don't seem to check if
create_in_format_blob fails either so perhaps it's not worth it.


> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -665,6 +665,56 @@ 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;
Please drop the leading __ from the type names in UAPI headers.

Regards,
Emil