Re: [PATCH] drm/syncobj: Extend EXPORT_SYNC_FILE for timeline syncobjs
From: Rob Clark
Date: Wed Mar 26 2025 - 10:52:26 EST
On Wed, Mar 26, 2025 at 7:41 AM Christian König
<christian.koenig@xxxxxxx> wrote:
>
> Am 26.03.25 um 15:39 schrieb Rob Clark:
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > Add support for exporting a dma_fence fd for a specific point on a
> > timeline.
>
> Looks good on first glance. What's the userspace use case?
Timeline syncobj support for vtest/vpipe[1][2].. since core
virglrender and drm native ctx works in terms of fences (since in the
VM case, everything is a fence below the guest kernel uabi), we need
to be able to turn a point on a timeline back into a fence fd. (Plus
it seemed like an odd omission from the existing uabi.)
BR,
-R
[1] https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33433
[2] https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/805
>
> Regards,
> Christian.
>
> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_syncobj.c | 8 ++++++--
> > include/uapi/drm/drm.h | 2 ++
> > 2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> > index 4f2ab8a7b50f..eb7a2dd2e261 100644
> > --- a/drivers/gpu/drm/drm_syncobj.c
> > +++ b/drivers/gpu/drm/drm_syncobj.c
> > @@ -762,7 +762,7 @@ static int drm_syncobj_import_sync_file_fence(struct drm_file *file_private,
> > }
> >
> > static int drm_syncobj_export_sync_file(struct drm_file *file_private,
> > - int handle, int *p_fd)
> > + int handle, u64 point, int *p_fd)
> > {
> > int ret;
> > struct dma_fence *fence;
> > @@ -772,7 +772,7 @@ static int drm_syncobj_export_sync_file(struct drm_file *file_private,
> > if (fd < 0)
> > return fd;
> >
> > - ret = drm_syncobj_find_fence(file_private, handle, 0, 0, &fence);
> > + ret = drm_syncobj_find_fence(file_private, handle, point, 0, &fence);
> > if (ret)
> > goto err_put_fd;
> >
> > @@ -882,8 +882,12 @@ drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data,
> >
> > if (args->flags & DRM_SYNCOBJ_HANDLE_TO_FD_FLAGS_EXPORT_SYNC_FILE)
> > return drm_syncobj_export_sync_file(file_private, args->handle,
> > + args->point,
> > &args->fd);
> >
> > + if (args->point)
> > + return -EINVAL;
> > +
> > return drm_syncobj_handle_to_fd(file_private, args->handle,
> > &args->fd);
> > }
> > diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> > index 7fba37b94401..c71a8f4439f2 100644
> > --- a/include/uapi/drm/drm.h
> > +++ b/include/uapi/drm/drm.h
> > @@ -912,6 +912,8 @@ struct drm_syncobj_handle {
> >
> > __s32 fd;
> > __u32 pad;
> > +
> > + __u64 point;
> > };
> >
> > struct drm_syncobj_transfer {
>