diff options
Diffstat (limited to 'include/uapi/drm')
| -rw-r--r-- | include/uapi/drm/xe_drm.h | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h index f62689ca861a..cac607a30f6d 100644 --- a/include/uapi/drm/xe_drm.h +++ b/include/uapi/drm/xe_drm.h @@ -811,6 +811,32 @@ struct drm_xe_gem_create { /** * struct drm_xe_gem_mmap_offset - Input of &DRM_IOCTL_XE_GEM_MMAP_OFFSET + * + * The @flags can be: + * - %DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER - For user to query special offset + * for use in mmap ioctl. Writing to the returned mmap address will generate a + * PCI memory barrier with low overhead (avoiding IOCTL call as well as writing + * to VRAM which would also add overhead), acting like an MI_MEM_FENCE + * instruction. + * + * Note: The mmap size can be at most 4K, due to HW limitations. As a result + * this interface is only supported on CPU architectures that support 4K page + * size. The mmap_offset ioctl will detect this and gracefully return an + * error, where userspace is expected to have a different fallback method for + * triggering a barrier. + * + * Roughly the usage would be as follows: + * + * .. code-block:: C + * + * struct drm_xe_gem_mmap_offset mmo = { + * .handle = 0, // must be set to 0 + * .flags = DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER, + * }; + * + * err = ioctl(fd, DRM_IOCTL_XE_GEM_MMAP_OFFSET, &mmo); + * map = mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, mmo.offset); + * map[i] = 0xdeadbeaf; // issue barrier */ struct drm_xe_gem_mmap_offset { /** @extensions: Pointer to the first extension struct, if any */ @@ -819,7 +845,8 @@ struct drm_xe_gem_mmap_offset { /** @handle: Handle for the object being mapped. */ __u32 handle; - /** @flags: Must be zero */ +#define DRM_XE_MMAP_OFFSET_FLAG_PCI_BARRIER (1 << 0) + /** @flags: Flags */ __u32 flags; /** @offset: The fake offset to use for subsequent mmap call */ |