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| author | Simon Ser <contact@emersion.fr> | 2023-02-16 13:09:45 +0000 |
|---|---|---|
| committer | Simon Ser <contact@emersion.fr> | 2023-02-17 10:30:49 +0100 |
| commit | 158350aae16a4e666e261da0bb4d91c0601a3edd (patch) | |
| tree | ce21eea1acc26f34073c76e0f99a69412b794d25 /include/uapi/drm/drm.h | |
| parent | 9a87e28da1f3563977bef1b6754e3d5d6895546f (diff) | |
| download | linux-158350aae16a4e666e261da0bb4d91c0601a3edd.tar.gz linux-158350aae16a4e666e261da0bb4d91c0601a3edd.tar.bz2 linux-158350aae16a4e666e261da0bb4d91c0601a3edd.zip | |
drm: document DRM_IOCTL_GEM_CLOSE
This is a bit tricky, because of the ref'counting considerations.
See also [1] for more discussion about this topic. Since this is
kernel docs, I've decided to elaborate a bit less on the user-space
details.
[1]: https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110
Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Daniel Stone <daniel@fooishbar.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230216130934.156541-2-contact@emersion.fr
Diffstat (limited to 'include/uapi/drm/drm.h')
| -rw-r--r-- | include/uapi/drm/drm.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h index 642808520d92..c39fefb54613 100644 --- a/include/uapi/drm/drm.h +++ b/include/uapi/drm/drm.h @@ -972,6 +972,19 @@ extern "C" { #define DRM_IOCTL_GET_STATS DRM_IOR( 0x06, struct drm_stats) #define DRM_IOCTL_SET_VERSION DRM_IOWR(0x07, struct drm_set_version) #define DRM_IOCTL_MODESET_CTL DRM_IOW(0x08, struct drm_modeset_ctl) +/** + * DRM_IOCTL_GEM_CLOSE - Close a GEM handle. + * + * GEM handles are not reference-counted by the kernel. User-space is + * responsible for managing their lifetime. For example, if user-space imports + * the same memory object twice on the same DRM file description, the same GEM + * handle is returned by both imports, and user-space needs to ensure + * &DRM_IOCTL_GEM_CLOSE is performed once only. The same situation can happen + * when a memory object is allocated, then exported and imported again on the + * same DRM file description. The &DRM_IOCTL_MODE_GETFB2 IOCTL is an exception + * and always returns fresh new GEM handles even if an existing GEM handle + * already refers to the same memory object before the IOCTL is performed. + */ #define DRM_IOCTL_GEM_CLOSE DRM_IOW (0x09, struct drm_gem_close) #define DRM_IOCTL_GEM_FLINK DRM_IOWR(0x0a, struct drm_gem_flink) #define DRM_IOCTL_GEM_OPEN DRM_IOWR(0x0b, struct drm_gem_open) |