[Mesa-dev] [PATCH] gbm/dri: Flush after unmap

[Emil Velikov]

Hi Thomas,

On 28 March 2017 at 20:39, Thomas Hellstrom <thellstrom at vmware.com> wrote:
> Drivers may queue dma operations on the context at unmap time so we need
> to flush to make sure the data gets to the bo. Ideally the application
> would take care of this, but since there appears to be no exported gbm
> flush functionality we need to explicitly flush at unmap time.
>
> This fixes a problem where kmscube on vmwgfx in rgba textured mode would
> render using an uninitialized texture rather than the intended
> rgba pattern.
>
I haven't checked but the issue should not be restricted to vmwgfx, right ?

Perhaps we should add the following
Fixes: 8aeb6d768b4 ("gbm: Add map/unmap functions")
CC: <mesa-stable at lists.freedesktop.org>

> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
> ---
>  src/gbm/backends/dri/gbm_dri.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/src/gbm/backends/dri/gbm_dri.c b/src/gbm/backends/dri/gbm_dri.c
> index ac7ede8..6c2244c 100644
> --- a/src/gbm/backends/dri/gbm_dri.c
> +++ b/src/gbm/backends/dri/gbm_dri.c
> @@ -243,7 +243,7 @@ struct dri_extension_match {
>  };
>
>  static struct dri_extension_match dri_core_extensions[] = {
> -   { __DRI2_FLUSH, 1, offsetof(struct gbm_dri_device, flush) },
> +   { __DRI2_FLUSH, 4, offsetof(struct gbm_dri_device, flush) },
Currently the classic nouveau, radeon/r200 and i915 drivers do not
support v4 of the extension.
As-is this will 'break' them... if they ever worked to begin with.

One solution is to bail out (return -ENOSYS or similar) in map/unmap
API of the when the DRI module is too old.
Just some ^^ food for thought.

-Emil