[PATCH] drm: Repurpose reserved field of drm_event_vlank to crtc_id

[Ander Conselvan de Oliveira]

With the atomic API, it is possible that a single commit affects
multiple crtcs. If the user requests an event with that commit, one
event will be sent for each CRTC, but it is not possible to distinguish
which crtc an event is for in user space. To solve this, the reserved
field in struct drm_vblank_event is repurposed to include the crtc_id
which the event is for.

The DRM_CAP_CRTC_IN_VBLANK_EVENT is added to allow userspace to query if
the crtc field will be set properly.

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
---
 drivers/gpu/drm/drm_atomic.c | 7 +++++--
 drivers/gpu/drm/drm_crtc.c   | 1 +
 drivers/gpu/drm/drm_ioctl.c  | 3 +++
 include/uapi/drm/drm.h       | 3 ++-
 4 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 1066e4b..2a76d10 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1304,7 +1304,8 @@ EXPORT_SYMBOL(drm_atomic_async_commit);
  */
 
 static struct drm_pending_vblank_event *create_vblank_event(
-		struct drm_device *dev, struct drm_file *file_priv, uint64_t user_data)
+		struct drm_device *dev, struct drm_file *file_priv,
+		uint64_t user_data, struct drm_crtc *crtc)
 {
 	struct drm_pending_vblank_event *e = NULL;
 	unsigned long flags;
@@ -1328,6 +1329,7 @@ static struct drm_pending_vblank_event *create_vblank_event(
 	e->event.base.type = DRM_EVENT_FLIP_COMPLETE;
 	e->event.base.length = sizeof e->event;
 	e->event.user_data = user_data;
+	e->event.crtc_id = crtc->base.id;
 	e->base.event = &e->event.base;
 	e->base.file_priv = file_priv;
 	e->base.destroy = (void (*) (struct drm_pending_event *)) kfree;
@@ -1529,7 +1531,8 @@ retry:
 		for_each_crtc_in_state(state, crtc, crtc_state, i) {
 			struct drm_pending_vblank_event *e;
 
-			e = create_vblank_event(dev, file_priv, arg->user_data);
+			e = create_vblank_event(dev, file_priv, arg->user_data,
+						crtc);
 			if (!e) {
 				ret = -ENOMEM;
 				goto out;
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 33d877c..98fe624 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -5212,6 +5212,7 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 		e->event.base.type = DRM_EVENT_FLIP_COMPLETE;
 		e->event.base.length = sizeof(e->event);
 		e->event.user_data = page_flip->user_data;
+		e->event.crtc_id = crtc->base.id;
 		e->base.event = &e->event.base;
 		e->base.file_priv = file_priv;
 		e->base.destroy =
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index b1d303f..152aeba 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -312,6 +312,9 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
 	case DRM_CAP_ADDFB2_MODIFIERS:
 		req->value = dev->mode_config.allow_fb_modifiers;
 		break;
+	case DRM_CAP_CRTC_IN_VBLANK_EVENT:
+		req->value = 1;
+		break;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 3801584..ecd9e96 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -631,6 +631,7 @@ struct drm_gem_open {
 #define DRM_CAP_CURSOR_WIDTH		0x8
 #define DRM_CAP_CURSOR_HEIGHT		0x9
 #define DRM_CAP_ADDFB2_MODIFIERS	0x10
+#define DRM_CAP_CRTC_IN_VBLANK_EVENT	0x11
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {
@@ -826,7 +827,7 @@ struct drm_event_vblank {
 	__u32 tv_sec;
 	__u32 tv_usec;
 	__u32 sequence;
-	__u32 reserved;
+	__u32 crtc_id;
 };
 
 /* typedef area */
-- 
2.4.3