[PATCH] linux-dmabuf: clarify DRM_FORMAT_MOD_INVALID

[Chia-I Wu]

Talked with Daniel offline.  I sent a different version to revive the
format event.

On Mon, Apr 1, 2019 at 10:41 AM Chia-I Wu <olvaffe at gmail.com> wrote:

> DRM_FORMAT_MOD_INVALID means to derive the modifier from the dmabuf.
>
> Signed-off-by: Chia-I Wu <olvaffe at gmail.com>
> ---
>  .../linux-dmabuf/linux-dmabuf-unstable-v1.xml     | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> index 154afe2..7c76441 100644
> --- a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> +++ b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> @@ -28,6 +28,7 @@
>      <description summary="factory for creating dmabuf-based wl_buffers">
>        Following the interfaces from:
>
> https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
> +
> https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import_modifiers.txt
>        and the Linux DRM sub-system's AddFb2 ioctl.
>
>        This interface offers ways to create generic dmabuf-based
> @@ -129,8 +130,13 @@
>          binds to this interface. A roundtrip after binding guarantees that
>          the client has received all supported format-modifier pairs.
>
> +        For each supported format, DRM_FORMAT_MOD_INVALID (that is,
> +        modifier_hi == 0x00ffffff and modifier_lo == 0xffffffff) is
> implied
> +        and may not be sent.
> +
>          For the definition of the format and modifier codes, see the
> -        zwp_linux_buffer_params_v1::create request.
> +        zwp_linux_buffer_params_v1::create and
> zwp_linux_buffer_params_v1::add
> +        requests.
>        </description>
>        <arg name="format" type="uint" summary="DRM_FORMAT code"/>
>        <arg name="modifier_hi" type="uint"
> @@ -200,6 +206,13 @@
>          This request raises the PLANE_IDX error if plane_idx is too large.
>          The error PLANE_SET is raised if attempting to set a plane that
>          was already set.
> +
> +        Note that DRM_FORMAT_MOD_INVALID (that is, modifier_hi ==
> 0x00ffffff
> +        and modifier_lo == 0xffffffff) is always allowed and has a special
> +        meaning. It indicates that the modifier is derived from the
> dmabuf fd
> +        rather than explicitly specified. This use is discouraged and may
> not
> +        work if the dmabuf is imported to a different device than the
> device
> +        that allocated it.
>        </description>
>        <arg name="fd" type="fd" summary="dmabuf fd"/>
>        <arg name="plane_idx" type="uint" summary="plane index"/>
> --
> 2.21.0.392.gf8f6787159e-goog
>
>
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