drm/i915: Make i915 events part of uapi

Make the uevent strings part of the user API for people who wish to
write their own listeners.

v2: Make a space in the string concatenation. (Chad)
Use the "UEVENT" suffix intead of "EVENT" (Chad)
Make kernel-doc parseable Docbook comments (Daniel)

v3: Undid reset change introduced in last submission (Daniel)
Fixed up comments to address removal changes.

Thanks to Daniel Vetter for a majority of the parity error comments.

CC: Chad Versace <chad.versace@linux.intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -812,7 +812,7 @@ static void ivybridge_parity_work(struct work_struct *work)
 
 	mutex_unlock(&dev_priv->dev->struct_mutex);
 
-	parity_event[0] = "L3_PARITY_ERROR=1";
+	parity_event[0] = I915_L3_PARITY_UEVENT "=1";
 	parity_event[1] = kasprintf(GFP_KERNEL, "ROW=%d", row);
 	parity_event[2] = kasprintf(GFP_KERNEL, "BANK=%d", bank);
 	parity_event[3] = kasprintf(GFP_KERNEL, "SUBBANK=%d", subbank);
@@ -1402,9 +1402,9 @@ static void i915_error_work_func(struct work_struct *work)
 						    gpu_error);
 	struct drm_device *dev = dev_priv->dev;
 	struct intel_ring_buffer *ring;
-	char *error_event[] = { "ERROR=1", NULL };
-	char *reset_event[] = { "RESET=1", NULL };
-	char *reset_done_event[] = { "ERROR=0", NULL };
+	char *error_event[] = { I915_ERROR_UEVENT "=1", NULL };
+	char *reset_event[] = { I915_RESET_UEVENT "=1", NULL };
+	char *reset_done_event[] = { I915_ERROR_UEVENT "=0", NULL };
 	int i, ret;
 
 	kobject_uevent_env(&dev->primary->kdev.kobj, KOBJ_CHANGE, error_event);

include/uapi/drm/i915_drm.h

@@ -33,6 +33,30 @@
  * subject to backwards-compatibility constraints.
  */
 
+/**
+ * DOC: uevents generated by i915 on it's device node
+ *
+ * I915_L3_PARITY_UEVENT - Generated when the driver receives a parity mismatch
+ *	event from the gpu l3 cache. Additional information supplied is ROW,
+ *	BANK, SUBBANK of the affected cacheline. Userspace should keep track of
+ *	these events and if a specific cache-line seems to have a persistent
+ *	error remap it with the l3 remapping tool supplied in intel-gpu-tools.
+ *	The value supplied with the event is always 1.
+ *
+ * I915_ERROR_UEVENT - Generated upon error detection, currently only via
+ *	hangcheck. The error detection event is a good indicator of when things
+ *	began to go badly. The value supplied with the event is a 1 upon error
+ *	detection, and a 0 upon reset completion, signifying no more error
+ *	exists. NOTE: Disabling hangcheck or reset via module parameter will
+ *	cause the related events to not be seen.
+ *
+ * I915_RESET_UEVENT - Event is generated just before an attempt to reset the
+ *	the GPU. The value supplied with the event is always 1. NOTE: Disable
+ *	reset via module parameter will cause this event to not be seen.
+ */
+#define I915_L3_PARITY_UEVENT		"L3_PARITY_ERROR"
+#define I915_ERROR_UEVENT		"ERROR"
+#define I915_RESET_UEVENT		"RESET"
 
 /* Each region is a minimum of 16k, and there are at most 255 of them.
  */