drm: Add functions to setup/tear down drm_events.

An attempt at not spreading out the file_priv->event_space stuff out
quite so far and wide.  And I think fixes something in ipp_get_event()
that is broken (or if they are doing something more weird/subtle, then
breaks it in a fun way).

Based upon a patch from Rob Clark, rebased and polished.

v2: Spelling fixes (Alex).

Cc: Alex Deucher <alexdeucher@gmail.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Rob Clark <robdclark@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452548477-15905-3-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/drm_atomic.c

@@ -1347,44 +1347,23 @@ static struct drm_pending_vblank_event *create_vblank_event(
 		struct drm_device *dev, struct drm_file *file_priv, uint64_t user_data)
 {
 	struct drm_pending_vblank_event *e = NULL;
-	unsigned long flags;
-
-	spin_lock_irqsave(&dev->event_lock, flags);
-	if (file_priv->event_space < sizeof e->event) {
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-		goto out;
-	}
-	file_priv->event_space -= sizeof e->event;
-	spin_unlock_irqrestore(&dev->event_lock, flags);
+	int ret;
 
 	e = kzalloc(sizeof *e, GFP_KERNEL);
-	if (e == NULL) {
-		spin_lock_irqsave(&dev->event_lock, flags);
-		file_priv->event_space += sizeof e->event;
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-		goto out;
-	}
+	if (!e)
+		return NULL;
 
 	e->event.base.type = DRM_EVENT_FLIP_COMPLETE;
-	e->event.base.length = sizeof e->event;
+	e->event.base.length = sizeof(e->event);
 	e->event.user_data = user_data;
-	e->base.event = &e->event.base;
-	e->base.file_priv = file_priv;
-	e->base.destroy = (void (*) (struct drm_pending_event *)) kfree;
-
-out:
-	return e;
-}
 
-static void destroy_vblank_event(struct drm_device *dev,
-		struct drm_file *file_priv, struct drm_pending_vblank_event *e)
-{
-	unsigned long flags;
+	ret = drm_event_reserve_init(dev, file_priv, &e->base, &e->event.base);
+	if (ret) {
+		kfree(e);
+		return NULL;
+	}
 
-	spin_lock_irqsave(&dev->event_lock, flags);
-	file_priv->event_space += sizeof e->event;
-	spin_unlock_irqrestore(&dev->event_lock, flags);
-	kfree(e);
+	return e;
 }
 
 static int atomic_set_prop(struct drm_atomic_state *state,
@@ -1646,8 +1625,7 @@ out:
 			if (!crtc_state->event)
 				continue;
 
-			destroy_vblank_event(dev, file_priv,
-					     crtc_state->event);
+			drm_event_cancel_free(dev, &crtc_state->event->base);
 		}
 	}
 

drivers/gpu/drm/drm_crtc.c

@@ -5265,7 +5265,6 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 	struct drm_crtc *crtc;
 	struct drm_framebuffer *fb = NULL;
 	struct drm_pending_vblank_event *e = NULL;
-	unsigned long flags;
 	int ret = -EINVAL;
 
 	if (page_flip->flags & ~DRM_MODE_PAGE_FLIP_FLAGS ||
@@ -5316,41 +5315,26 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 	}
 
 	if (page_flip->flags & DRM_MODE_PAGE_FLIP_EVENT) {
-		ret = -ENOMEM;
-		spin_lock_irqsave(&dev->event_lock, flags);
-		if (file_priv->event_space < sizeof(e->event)) {
-			spin_unlock_irqrestore(&dev->event_lock, flags);
-			goto out;
-		}
-		file_priv->event_space -= sizeof(e->event);
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-
-		e = kzalloc(sizeof(*e), GFP_KERNEL);
-		if (e == NULL) {
-			spin_lock_irqsave(&dev->event_lock, flags);
-			file_priv->event_space += sizeof(e->event);
-			spin_unlock_irqrestore(&dev->event_lock, flags);
+		e = kzalloc(sizeof *e, GFP_KERNEL);
+		if (!e) {
+			ret = -ENOMEM;
 			goto out;
 		}
-
 		e->event.base.type = DRM_EVENT_FLIP_COMPLETE;
 		e->event.base.length = sizeof(e->event);
 		e->event.user_data = page_flip->user_data;
-		e->base.event = &e->event.base;
-		e->base.file_priv = file_priv;
-		e->base.destroy =
-			(void (*) (struct drm_pending_event *)) kfree;
+		ret = drm_event_reserve_init(dev, file_priv, &e->base, &e->event.base);
+		if (ret) {
+			kfree(e);
+			goto out;
+		}
 	}
 
 	crtc->primary->old_fb = crtc->primary->fb;
 	ret = crtc->funcs->page_flip(crtc, fb, e, page_flip->flags);
 	if (ret) {
-		if (page_flip->flags & DRM_MODE_PAGE_FLIP_EVENT) {
-			spin_lock_irqsave(&dev->event_lock, flags);
-			file_priv->event_space += sizeof(e->event);
-			spin_unlock_irqrestore(&dev->event_lock, flags);
-			kfree(e);
-		}
+		if (page_flip->flags & DRM_MODE_PAGE_FLIP_EVENT)
+			drm_event_cancel_free(dev, &e->base);
 		/* Keep the old fb, don't unref it. */
 		crtc->primary->old_fb = NULL;
 	} else {

drivers/gpu/drm/drm_fops.c

@@ -676,3 +676,70 @@ unsigned int drm_poll(struct file *filp, struct poll_table_struct *wait)
 	return mask;
 }
 EXPORT_SYMBOL(drm_poll);
+
+/**
+ * drm_event_reserve_init - init a DRM event and reserve space for it
+ * @dev: DRM device
+ * @file_priv: DRM file private data
+ * @p: tracking structure for the pending event
+ * @e: actual event data to deliver to userspace
+ *
+ * This function prepares the passed in event for eventual delivery. If the event
+ * doesn't get delivered (because the IOCTL fails later on, before queuing up
+ * anything) then the even must be cancelled and freed using
+ * drm_event_cancel_free().
+ *
+ * If callers embedded @p into a larger structure it must be allocated with
+ * kmalloc and @p must be the first member element.
+ *
+ * RETURNS:
+ *
+ * 0 on success or a negative error code on failure.
+ */
+int drm_event_reserve_init(struct drm_device *dev,
+			   struct drm_file *file_priv,
+			   struct drm_pending_event *p,
+			   struct drm_event *e)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&dev->event_lock, flags);
+
+	if (file_priv->event_space < e->length) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	file_priv->event_space -= e->length;
+
+	p->event = e;
+	p->file_priv = file_priv;
+
+	/* we *could* pass this in as arg, but everyone uses kfree: */
+	p->destroy = (void (*) (struct drm_pending_event *)) kfree;
+
+out:
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(drm_event_reserve_init);
+
+/**
+ * drm_event_cancel_free - free a DRM event and release it's space
+ * @dev: DRM device
+ * @p: tracking structure for the pending event
+ *
+ * This function frees the event @p initialized with drm_event_reserve_init()
+ * and releases any allocated space.
+ */
+void drm_event_cancel_free(struct drm_device *dev,
+			   struct drm_pending_event *p)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&dev->event_lock, flags);
+	p->file_priv->event_space += p->event->length;
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+	p->destroy(p);
+}
+EXPORT_SYMBOL(drm_event_cancel_free);

include/drm/drmP.h

@@ -925,8 +925,13 @@ ssize_t drm_read(struct file *filp, char __user *buffer,
 		 size_t count, loff_t *offset);
 int drm_release(struct inode *inode, struct file *filp);
 int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv);
-
 unsigned int drm_poll(struct file *filp, struct poll_table_struct *wait);
+int drm_event_reserve_init(struct drm_device *dev,
+			   struct drm_file *file_priv,
+			   struct drm_pending_event *p,
+			   struct drm_event *e);
+void drm_event_cancel_free(struct drm_device *dev,
+			   struct drm_pending_event *p);
 
 /* Misc. IOCTL support (drm_ioctl.c) */
 int drm_noop(struct drm_device *dev, void *data,