[PATCH] drm/syncobj: Add a signal ioctl

[Jason Ekstrand]

This IOCTL provides a mechanism for userspace to trigger a sync object
directly.  There are other ways that userspace can trigger a syncobj
such as submitting a dummy batch somewhere or hanging on to a triggered
sync_file and doing an import.  This just provides an easy way to
manually trigger the sync object without weird hacks.

The motivation for this IOCTL is Vulkan fences.  Vulkan lets you create
a fence already in the signaled state so that you can wait on it
immediatly without stalling.  We could also handle this with a new
create flag to ask the driver to create a syncobj that is already
signaled but the IOCTL seemed a bit cleaner and more generic.

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
---
 drivers/gpu/drm/drm_internal.h |  2 ++
 drivers/gpu/drm/drm_ioctl.c    |  2 ++
 drivers/gpu/drm/drm_syncobj.c  | 71 ++++++++++++++++++++++++++++++++++++++++++
 include/uapi/drm/drm.h         |  6 ++++
 4 files changed, 81 insertions(+)

diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 83f1615..fbc3f30 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -171,3 +171,5 @@ int drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
 			   struct drm_file *file_private);
 int drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
 			    struct drm_file *file_private);
+int drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
+			     struct drm_file *file_private);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 4185483..4d8f548 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -661,6 +661,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_RESET, drm_syncobj_reset_ioctl,
 		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_SIGNAL, drm_syncobj_signal_ioctl,
+		      DRM_UNLOCKED|DRM_RENDER_ALLOW),
 };
 
 #define DRM_CORE_IOCTL_COUNT	ARRAY_SIZE( drm_ioctls )
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 7dfdb98..8d3112e 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -831,3 +831,74 @@ drm_syncobj_reset_ioctl(struct drm_device *dev, void *data,
 
 	return 0;
 }
+
+struct drm_syncobj_null_fence {
+	struct dma_fence base;
+	spinlock_t lock;
+};
+
+static const char *drm_syncobj_null_fence_get_name(struct dma_fence *fence)
+{
+        return "syncobjnull";
+}
+
+static bool drm_syncobj_null_fence_enable_signaling(struct dma_fence *fence)
+{
+    dma_fence_enable_sw_signaling(fence);
+    return !dma_fence_is_signaled(fence);
+}
+
+static const struct dma_fence_ops drm_syncobj_null_fence_ops = {
+	.get_driver_name = drm_syncobj_null_fence_get_name,
+	.get_timeline_name = drm_syncobj_null_fence_get_name,
+	.enable_signaling = drm_syncobj_null_fence_enable_signaling,
+	.wait = dma_fence_default_wait,
+	.release = NULL,
+};
+
+static struct dma_fence *drm_syncobj_create_null_fence(void)
+{
+	struct drm_syncobj_null_fence *fence;
+	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
+	if (fence == NULL)
+		return NULL;
+
+	spin_lock_init(&fence->lock);
+	dma_fence_init(&fence->base, &drm_syncobj_null_fence_ops,
+		       &fence->lock, 0, 0);
+	return &fence->base;
+}
+
+int
+drm_syncobj_signal_ioctl(struct drm_device *dev, void *data,
+			 struct drm_file *file_private)
+{
+	struct drm_syncobj_signal *args = data;
+	struct drm_syncobj *syncobj;
+	struct dma_fence *null_fence;
+
+	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+		return -ENODEV;
+
+	if (args->flags != 0)
+		return -EINVAL;
+
+	syncobj = drm_syncobj_find(file_private, args->handle);
+	if (!syncobj)
+		return -ENOENT;
+
+	null_fence = drm_syncobj_create_null_fence();
+	if (!null_fence) {
+		drm_syncobj_put(syncobj);
+		return -ENOMEM;
+	}
+
+	dma_fence_signal(null_fence);
+
+	drm_syncobj_replace_fence(syncobj, null_fence);
+
+	dma_fence_put(null_fence);
+	drm_syncobj_put(syncobj);
+
+	return 0;
+}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index f8ec8fe..350a6a2 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -735,6 +735,11 @@ struct drm_syncobj_reset {
 	__u32 flags;
 };
 
+struct drm_syncobj_signal {
+	__u32 handle;
+	__u32 flags;
+};
+
 #if defined(__cplusplus)
 }
 #endif
@@ -859,6 +864,7 @@ extern "C" {
 #define DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE	DRM_IOWR(0xC2, struct drm_syncobj_handle)
 #define DRM_IOCTL_SYNCOBJ_WAIT		DRM_IOWR(0xC3, struct drm_syncobj_wait)
 #define DRM_IOCTL_SYNCOBJ_RESET		DRM_IOWR(0xC4, struct drm_syncobj_reset)
+#define DRM_IOCTL_SYNCOBJ_SIGNAL	DRM_IOWR(0xC5, struct drm_syncobj_signal)
 
 /**
  * Device specific ioctls should only be in their respective headers
-- 
2.5.0.400.gff86faf