[PATCH v2] linux-dmabuf: clarify DRM_FORMAT_MOD_INVALID
contact at emersion.fr
Tue Apr 16 18:54:48 UTC 2019
On Tuesday, April 16, 2019 8:06 PM, Chia-I Wu <olvaffe at gmail.com> wrote:
> DRM_FORMAT_MOD_INVALID means to derive the modifier from the dmabuf.
> It provides legacy support and makes it easier to replace wl_drm.
> Signed-off-by: Chia-I Wu <olvaffe at gmail.com>
> .../linux-dmabuf/linux-dmabuf-unstable-v1.xml | 16 +++++++++++++++-
> 1 file changed, 15 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..e1ac82f 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_modifiers.txt
> and the Linux DRM sub-system's AddFb2 ioctl.
> This interface offers ways to create generic dmabuf-based
> @@ -129,8 +130,16 @@
> binds to this interface. A roundtrip after binding guarantees that
> the client has received all supported format-modifier pairs.
> + For legacy support, DRM_FORMAT_MOD_INVALID (that is, modifier_hi ==
> + 0x00ffffff and modifier_lo == 0xffffffff) is considered a valid
> + modifier. It indicates that the server can support the format with an
> + implicit modifier. When a plane has DRM_FORMAT_MOD_INVALID as its
> + modifier, the effective modifier will be derived from the dmabuf
> + rather than the explicitly specified value.
"DRM_FORMAT_MOD_INVALID is […] valid […]": the wording is a little weird.
> 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.
> <arg name="format" type="uint" summary="DRM_FORMAT code"/>
> <arg name="modifier_hi" type="uint"
> @@ -197,6 +206,11 @@
> compression, etc. driver-specific modifications to the base format
> defined by the DRM fourcc code.
> + Warning: It should be an error if the format/modifier pair was not
> + advertised with the modifier event. This is not enforced yet because
> + some implementations always accept DRM_FORMAT_MOD_INVALID. Also
> + version 2 of this protocol does not have the modifier event.
I thought the plan was to bump the version to make it a protocol error?
> 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.
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