tools headers UAPI: Sync the drm/drm.h with the kernel sources

Picking the changes from:

  60687716 ("drm: document DRM_IOCTL_PRIME_HANDLE_TO_FD and PRIME_FD_TO_HANDLE")
  61a55f8b ("drm: document expectations for GETFB2 handles")
  158350aa ("drm: document DRM_IOCTL_GEM_CLOSE")

Silencing these perf build warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/drm/drm.h' differs from latest version at 'include/uapi/drm/drm.h'
  diff -u tools/include/uapi/drm/drm.h include/uapi/drm/drm.h

No changes in tooling as these are just C comment documentation changes.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongson-kernel@lists.loongnix.cn
Link: https://lore.kernel.org/r/7552c61660bf079f2979fdcbcef8e921255f877a.1683712945.git.siyanteng@loongson.cnSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/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)
@@ -1012,7 +1025,37 @@ extern "C" {
 #define DRM_IOCTL_UNLOCK		DRM_IOW( 0x2b, struct drm_lock)
 #define DRM_IOCTL_FINISH		DRM_IOW( 0x2c, struct drm_lock)
 
+/**
+ * DRM_IOCTL_PRIME_HANDLE_TO_FD - Convert a GEM handle to a DMA-BUF FD.
+ *
+ * User-space sets &drm_prime_handle.handle with the GEM handle to export and
+ * &drm_prime_handle.flags, and gets back a DMA-BUF file descriptor in
+ * &drm_prime_handle.fd.
+ *
+ * The export can fail for any driver-specific reason, e.g. because export is
+ * not supported for this specific GEM handle (but might be for others).
+ *
+ * Support for exporting DMA-BUFs is advertised via &DRM_PRIME_CAP_EXPORT.
+ */
 #define DRM_IOCTL_PRIME_HANDLE_TO_FD    DRM_IOWR(0x2d, struct drm_prime_handle)
+/**
+ * DRM_IOCTL_PRIME_FD_TO_HANDLE - Convert a DMA-BUF FD to a GEM handle.
+ *
+ * User-space sets &drm_prime_handle.fd with a DMA-BUF file descriptor to
+ * import, and gets back a GEM handle in &drm_prime_handle.handle.
+ * &drm_prime_handle.flags is unused.
+ *
+ * If an existing GEM handle refers to the memory object backing the DMA-BUF,
+ * that GEM handle is returned. Therefore user-space which needs to handle
+ * arbitrary DMA-BUFs must have a user-space lookup data structure to manually
+ * reference-count duplicated GEM handles. For more information see
+ * &DRM_IOCTL_GEM_CLOSE.
+ *
+ * The import can fail for any driver-specific reason, e.g. because import is
+ * only supported for DMA-BUFs allocated on this DRM device.
+ *
+ * Support for importing DMA-BUFs is advertised via &DRM_PRIME_CAP_IMPORT.
+ */
 #define DRM_IOCTL_PRIME_FD_TO_HANDLE    DRM_IOWR(0x2e, struct drm_prime_handle)
 
 #define DRM_IOCTL_AGP_ACQUIRE		DRM_IO(  0x30)
@@ -1104,8 +1147,13 @@ extern "C" {
  * struct as the output.
  *
  * If the client is DRM master or has &CAP_SYS_ADMIN, &drm_mode_fb_cmd2.handles
- * will be filled with GEM buffer handles. Planes are valid until one has a
- * zero handle -- this can be used to compute the number of planes.
+ * will be filled with GEM buffer handles. Fresh new GEM handles are always
+ * returned, even if another GEM handle referring to the same memory object
+ * already exists on the DRM file description. The caller is responsible for
+ * removing the new handles, e.g. via the &DRM_IOCTL_GEM_CLOSE IOCTL. The same
+ * new handle will be returned for multiple planes in case they use the same
+ * memory object. Planes are valid until one has a zero handle -- this can be
+ * used to compute the number of planes.
  *
  * Otherwise, &drm_mode_fb_cmd2.handles will be zeroed and planes are valid
  * until one has a zero &drm_mode_fb_cmd2.pitches.
@@ -1113,6 +1161,11 @@ extern "C" {
  * If the framebuffer has a format modifier, &DRM_MODE_FB_MODIFIERS will be set
  * in &drm_mode_fb_cmd2.flags and &drm_mode_fb_cmd2.modifier will contain the
  * modifier. Otherwise, user-space must ignore &drm_mode_fb_cmd2.modifier.
+ *
+ * To obtain DMA-BUF FDs for each plane without leaking GEM handles, user-space
+ * can export each handle via &DRM_IOCTL_PRIME_HANDLE_TO_FD, then immediately
+ * close each unique handle via &DRM_IOCTL_GEM_CLOSE, making sure to not
+ * double-close handles which are specified multiple times in the array.
  */
 #define DRM_IOCTL_MODE_GETFB2		DRM_IOWR(0xCE, struct drm_mode_fb_cmd2)