[PATCH v2] linux-dmabuf: clarify DRM_FORMAT_MOD_INVALID
olvaffe at gmail.com
Tue Apr 16 17:06:43 UTC 2019
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
@@ -28,6 +28,7 @@
<description summary="factory for creating dmabuf-based wl_buffers">
Following the interfaces from:
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.
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
<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.
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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