https://bugs.kde.org/show_bug.cgi?id=448284
Bug ID: 448284
Summary: Mesa commit 83916ae0, "egl/wayland: add initial
dma-buf feedback support" interacts badly with
kwin_wayland's dma-buf feedback code, causing Mesa to
fallback to llvmpipe
Product: kwin
Version: git master
Platform: Compiled Sources
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: egl
Assignee: kwin-bugs-n...@kde.org
Reporter: kyle.de...@mykolab.com
Target Milestone: ---
Mesa bug report: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5844
Relevant comment from Leandro Ribeiro:
"Kwin is exposing zwp_linux_dmabuf_v1 version 4 and then advertising
formats/modifiers through dma-buf modifier events. From zwp_linux_dmabuf_v1
version 4 onward, modifier events should not be advertised. Instead, clients
should receive them using dma-buf feedback interface. See
https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/main/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml#L156.
This is one issue that I can see from this log, and that should be fixed in
Kwin.
Because of what I've described above, in Mesa EGL we ignore the dma-buf
modifier events if zwp_linux_dmabuf_v1 version is >= 4. As Mesa EGL is unable
to map the dma-buf feedback format table that it receives from Kwin, Mesa EGL
didn't receive formats/modifiers from zwp_linux_dmabuf_v1. IIUC this is why it
fallback to llvmpipe and you have 4 FPS.
> How do I get at the dma-buf feedback format table event data?
I was thinking about adding some prints to
default_dmabuf_feedback_format_table() (in platform_wayland.c). In this
function Mesa EGL receives the fd of the format table from Kwin. But thinking
twice, I don't think this would be very helpful. Instead, it's better to debug
Kwin to find out what's wrong with the format table fd it sends to Mesa EGL.
I've tried to take a look at the commit that added dma-buf feedback to Kwin,
but I'm unfamiliar with the code. Maybe the person who wrote the commit can
help you?"
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