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>

1 files changed, 67 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 1551d65db24e..f9eacbb2d1dd 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/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);