[RFC 8/8] drm/fence: add out-fences support

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Support DRM out-fences creating a sync_file with a fence for each crtc
update with the DRM_MODE_ATOMIC_OUT_FENCE flag.

We then send an struct drm_out_fences array with the out-fences fds back in
the drm_atomic_ioctl() as an out arg in the out_fences_ptr field.

struct drm_out_fences {
	__u32   crtc_id;
	__u32   fd;
};

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/gpu/drm/drm_atomic.c        | 109 +++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/drm_atomic_helper.c |   1 +
 include/drm/drm_crtc.h              |   3 +
 include/uapi/drm/drm_mode.h         |   7 +++
 4 files changed, 119 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 0b95526..af6e051 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1560,6 +1560,103 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_atomic_clean_old_fb);
 
+static int drm_atomic_get_out_fences(struct drm_device *dev,
+				     struct drm_atomic_state *state,
+				     uint32_t __user *out_fences_ptr,
+				     uint64_t count_out_fences,
+				     uint64_t user_data)
+{
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	struct drm_out_fences *out_fences;
+	struct sync_file **sync_file;
+	int num_fences = 0;
+	int i, ret;
+
+	out_fences = kcalloc(count_out_fences, sizeof(*out_fences),
+			     GFP_KERNEL);
+	if (!out_fences)
+		return -ENOMEM;
+
+	sync_file = kcalloc(count_out_fences, sizeof(*sync_file),
+			     GFP_KERNEL);
+	if (!sync_file) {
+		kfree(out_fences);
+		return -ENOMEM;
+	}
+
+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
+		struct drm_pending_vblank_event *e;
+		struct fence *fence;
+		char name[32];
+		int fd;
+
+		fence = sync_timeline_create_fence(crtc->timeline,
+						   crtc->fence_seqno);
+		if (!fence) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		snprintf(name, sizeof(name), "crtc-%d_%lu",
+			 drm_crtc_index(crtc), crtc->fence_seqno++);
+
+		sync_file[i] = sync_file_create(name, fence);
+		if(!sync_file[i]) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		fd = get_unused_fd_flags(O_CLOEXEC);
+		if (fd < 0) {
+			ret = fd;
+			goto out;
+		}
+
+		sync_file_install(sync_file[i], fd);
+
+		if (crtc_state->event) {
+			crtc_state->event->base.fence = fence;
+		} else {
+			e = create_vblank_event(dev, NULL, fence, user_data);
+			if (!e) {
+				put_unused_fd(fd);
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			crtc_state->event = e;
+		}
+		if (num_fences > count_out_fences) {
+			put_unused_fd(fd);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		fence_get(fence);
+
+		out_fences[num_fences].crtc_id = crtc->base.id;
+		out_fences[num_fences].fd = fd;
+		num_fences++;
+	}
+
+	if (copy_to_user(out_fences_ptr, out_fences,
+			 num_fences * sizeof(*out_fences))) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	return 0;
+
+out:
+	for (i = 0 ; i < count_out_fences ; i++) {
+		if (sync_file[i])
+			sync_file_put(sync_file[i]);
+	}
+
+	return ret;
+}
+
 int drm_mode_atomic_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv)
 {
@@ -1568,6 +1665,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	uint32_t __user *count_props_ptr = (uint32_t __user *)(unsigned long)(arg->count_props_ptr);
 	uint32_t __user *props_ptr = (uint32_t __user *)(unsigned long)(arg->props_ptr);
 	uint64_t __user *prop_values_ptr = (uint64_t __user *)(unsigned long)(arg->prop_values_ptr);
+	uint32_t __user *out_fences_ptr = (uint32_t __user *)(unsigned long)(arg->out_fences_ptr);
 	unsigned int copied_objs, copied_props;
 	struct drm_atomic_state *state;
 	struct drm_modeset_acquire_ctx ctx;
@@ -1601,7 +1699,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 
 	/* can't test and expect an event at the same time. */
 	if ((arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) &&
-			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
+			(arg->flags & (DRM_MODE_PAGE_FLIP_EVENT
+			 | DRM_MODE_ATOMIC_OUT_FENCE)))
 		return -EINVAL;
 
 	drm_modeset_acquire_init(&ctx, 0);
@@ -1693,6 +1792,14 @@ retry:
 		}
 	}
 
+	if (arg->flags & DRM_MODE_ATOMIC_OUT_FENCE) {
+		ret = drm_atomic_get_out_fences(dev, state, out_fences_ptr,
+						arg->count_out_fences,
+						arg->user_data);
+		if (ret < 0)
+			goto out;
+	}
+
 	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
 		/*
 		 * Unlike commit, check_only does not clean up state.
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 6ed8339..15ba3a8 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -31,6 +31,7 @@
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_atomic_helper.h>
 #include <linux/fence.h>
+#include <linux/sync_file.h>
 
 /**
  * DOC: overview
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 7934178..53e4e71 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -717,6 +717,7 @@ struct drm_crtc_funcs {
  * @properties: property tracking for this CRTC
  * @state: current atomic state for this CRTC
  * @timeline: sync timeline for fence sigalling
+ * @fence_seqno: seqno variable to create fences
  * @acquire_ctx: per-CRTC implicit acquire context used by atomic drivers for
  * 	legacy IOCTLs
  *
@@ -773,7 +774,9 @@ struct drm_crtc {
 
 	struct drm_crtc_state *state;
 
+	/* for out-fences */
 	struct sync_timeline *timeline;
+	unsigned long fence_seqno;
 
 	/*
 	 * For legacy crtc IOCTLs so that atomic drivers can get at the locking
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 39905cc..4cdcd22 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -592,6 +592,11 @@ struct drm_mode_destroy_dumb {
 		DRM_MODE_ATOMIC_ALLOW_MODESET |\
 		DRM_MODE_ATOMIC_OUT_FENCE)
 
+struct drm_out_fences {
+	__u32	crtc_id;
+	__u32	fd;
+};
+
 struct drm_mode_atomic {
 	__u32 flags;
 	__u32 count_objs;
@@ -601,6 +606,8 @@ struct drm_mode_atomic {
 	__u64 prop_values_ptr;
 	__u64 reserved;
 	__u64 user_data;
+	__u64 count_out_fences;
+	__u64 out_fences_ptr;
 };
 
 /**
-- 
2.5.5