Hi Jason, this mail also somehow ended up to be rejected by our spam filter and I'm not sure why :( Anyway, feel free to add my Acked-by. From the technical point I would give an r-b as well, but I'm not a native speaker of English. Cheers, Christian. Am 08.08.19 um 06:47 schrieb Jason Ekstrand: > Christan, any thoughts on v2? > > --Jason > > > On August 7, 2019 09:06:47 Lionel Landwerlin > <lionel.g.landwerlin@xxxxxxxxx> wrote: > >> On 06/08/2019 19:19, Jason Ekstrand wrote: >>> This patch only brings the syncobj documentation up-to-date for the >>> original form of syncobj. It does not contain any information about >>> the >>> design of timeline syncobjs. >>> >>> v2: Incorporate feedback from Lionel and Christian: >>> - Mention actual ioctl and flag names >>> - Better language around reference counting >>> - Misc. language cleanups >>> >>> Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx> >> >> Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx> >> >>> --- >>> drivers/gpu/drm/drm_syncobj.c | 98 >>> +++++++++++++++++++++++++++++++---- >>> 1 file changed, 87 insertions(+), 11 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/drm_syncobj.c >>> b/drivers/gpu/drm/drm_syncobj.c >>> index 1438dcb3ebb1..4b5c7b0ed714 100644 >>> --- a/drivers/gpu/drm/drm_syncobj.c >>> +++ b/drivers/gpu/drm/drm_syncobj.c >>> @@ -29,21 +29,97 @@ >>> /** >>> * DOC: Overview >>> * >>> - * DRM synchronisation objects (syncobj, see struct &drm_syncobj) are >>> - * persistent objects that contain an optional fence. The Ok,fence >>> can be updated >>> - * with a new fence, or be NULL. >>> + * DRM synchronisation objects (syncobj, see struct &drm_syncobj) >>> provide a >>> + * container for a synchronization primitive which can be used by >>> userspace >>> + * to explicitly synchronize GPU commands, can be shared between >>> userspace >>> + * processes, and can be shared between different DRM drivers. >>> + * Their primary use-case is to implement Vulkan fences and >>> semaphores. >>> + * The syncobj userspace API provides ioctls for several operations: >>> * >>> - * syncobj's can be waited upon, where it will wait for the underlying >>> - * fence. >>> + * - Creation and destruction of syncobjs >>> + * - Import and export of syncobjs to/from a syncobj file descriptor >>> + * - Import and export a syncobj's underlying fence to/from a sync >>> file >>> + * - Reset a syncobj (set its fence to NULL) >>> + * - Signal a syncobj (set a trivially signaled fence) >>> + * - Wait for a syncobj's fence to appear and be signaled >>> * >>> - * syncobj's can be export to fd's and back, these fd's are opaque and >>> - * have no other use case, except passing the syncobj between >>> processes. >>> + * At it's core, a syncobj is simply a wrapper around a pointer to >>> a struct >>> + * &dma_fence which may be NULL. >>> + * When a syncobj is first created, its pointer is either NULL or a >>> pointer >>> + * to an already signaled fence depending on whether the >>> + * &DRM_SYNCOBJ_CREATE_SIGNALED flag is passed to >>> + * &DRM_IOCTL_SYNCOBJ_CREATE. >>> + * When GPU work which signals a syncobj is enqueued in a DRM driver, >>> + * the syncobj fence is replaced with a fence which will be >>> signaled by the >>> + * completion of that work. >>> + * When GPU work which waits on a syncobj is enqueued in a DRM >>> driver, the >>> + * driver retrieves syncobj's current fence at the time the work is >>> enqueued >>> + * waits on that fence before submitting the work to hardware. >>> + * If the syncobj's fence is NULL, the enqueue operation is >>> expected to fail. >>> + * All manipulation of the syncobjs's fence happens in terms of the >>> current >>> + * fence at the time the ioctl is called by userspace regardless of >>> whether >>> + * that operation is an immediate host-side operation (signal or >>> reset) or >>> + * or an operation which is enqueued in some driver queue. >>> + * &DRM_IOCTL_SYNCOBJ_RESET and &DRM_IOCTL_SYNCOBJ_SIGNAL can be >>> used to >>> + * manipulate a syncobj from the host by resetting its pointer to >>> NULL or >>> + * setting its pointer to a fence which is already signaled. >>> * >>> - * Their primary use-case is to implement Vulkan fences and >>> semaphores. >>> * >>> - * syncobj have a kref reference count, but also have an optional >>> file. >>> - * The file is only created once the syncobj is exported. >>> - * The file takes a reference on the kref. >>> + * Host-side wait on syncobjs >>> + * -------------------------- >>> + * >>> + * &DRM_IOCTL_SYNCOBJ_WAIT takes an array of syncobj handles and >>> does a >>> + * host-side wait on all of the syncobj fences simultaneously. >>> + * If &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL is set, the wait ioctl will >>> wait on >>> + * all of the syncobj fences to be signaled before it returns. >>> + * Otherwise, it returns once at least one syncobj fence has been >>> signaled >>> + * and the index of a signaled fence is written back to the client. >>> + * >>> + * Unlike the enqueued GPU work dependencies which fail if they see >>> a NULL >>> + * fence in a syncobj, if &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT >>> is set, >>> + * the host-side wait will first wait for the syncobj to receive a >>> non-NULL >>> + * fence and then wait on that fence. >>> + * If &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT is not set and any >>> one of the >>> + * syncobjs in the array has a NULL fence, -EINVAL will be returned. >>> + * Assuming the syncobj starts off with a NULL fence, this allows a >>> client >>> + * to do a host wait in one thread (or process) which waits on GPU >>> work >>> + * submitted in another thread (or process) without having to manually >>> + * synchronize between the two. >>> + * This requirement is inherited from the Vulkan fence API. >>> + * >>> + * >>> + * Import/export of syncobjs >>> + * ------------------------- >>> + * >>> + * &DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE and &DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD >>> + * provide two mechanisms for import/export of syncobjs. >>> + * >>> + * The first lets the client import or export an entire syncobj to >>> a file >>> + * descriptor. >>> + * These fd's are opaque and have no other use case, except passing >>> the >>> + * syncobj between processes. >>> + * All exported file descriptors and any syncobj handles created as a >>> + * result of importing those file descriptors own a reference to the >>> + * same underlying struct &drm_syncobj and the syncobj can be used >>> + * persistently across all the processes with which it is shared. >>> + * The syncobj is freed only once the last reference is dropped. >>> + * Unlike dma-buf, importing a syncobj creates a new handle (with >>> its own >>> + * reference) for every import instead of de-duplicating. >>> + * The primary use-case of this persistent import/export is for shared >>> + * Vulkan fences and semaphores. >>> + * >>> + * The second import/export mechanism, which is indicated by >>> + * &DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_IMPORT_SYNC_FILE or >>> + * &DRM_SYNCOBJ_HANDLE_TO_FD_FLAGS_EXPORT_SYNC_FILE lets the client >>> + * import/export the syncobj's current fence from/to a &sync_file. >>> + * When a syncobj is exported to a sync file, that sync file wraps the >>> + * sycnobj's fence at the time of export and any later signal or reset >>> + * operations on the syncobj will not affect the exported sync file. >>> + * When a sync file is imported into a syncobj, the syncobj's fence >>> is set >>> + * to the fence wrapped by that sync file. >>> + * Because sync files are immutable, resetting or signaling the >>> syncobj >>> + * will not affect any sync files whose fences have been imported >>> into the >>> + * syncobj. >>> */ >>> >>> #include <linux/anon_inodes.h> > > > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
