drm: Pass CRTC ID in userspace vblank events

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.

[daniels: Rebased, using Maarten's forward-port.]

Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: Daniel Stone <daniels@collabora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170404165221.28240-2-daniels@collabora.com

3 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 9f4241f0dd9c..865e3ee4d743 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -286,6 +286,9 @@ 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/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index dac1b2593cb1..8c866cac62dd 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1026,6 +1026,7 @@ void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
 
         e->pipe = pipe;
         e->event.sequence = drm_vblank_count(dev, pipe);
+        e->event.crtc_id = crtc->base.id;
         list_add_tail(&e->base.link, &dev->vblank_event_list);
 }
 EXPORT_SYMBOL(drm_crtc_arm_vblank_event);
@@ -1056,6 +1057,7 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
                 now = get_drm_timestamp();
         }
         e->pipe = pipe;
+        e->event.crtc_id = crtc->base.id;
         send_vblank_event(dev, e, seq, &now);
 }
 EXPORT_SYMBOL(drm_crtc_send_vblank_event);
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index b2c52843bc70..42d9f64ce416 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -647,6 +647,7 @@ struct drm_gem_open {
 #define DRM_CAP_CURSOR_HEIGHT           0x9
 #define DRM_CAP_ADDFB2_MODIFIERS        0x10
 #define DRM_CAP_PAGE_FLIP_TARGET        0x11
+#define DRM_CAP_CRTC_IN_VBLANK_EVENT    0x12
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {
@@ -851,7 +852,7 @@ struct drm_event_vblank {
         __u32 tv_sec;
         __u32 tv_usec;
         __u32 sequence;
-        __u32 reserved;
+        __u32 crtc_id; /* 0 on older kernels that do not support this */
 };
 
 /* typedef area */