drm/i915: export error state to string conversion

In preparation for accessing error state from sysfs, export
error state to string conversion function. Also tuck buffer
error handling inside the function.
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -830,15 +830,8 @@ static void i915_ring_error_state(struct drm_i915_error_state_buf *m,
 	err_printf(m, "  ring->tail: 0x%08x\n", error->cpu_ring_tail[ring]);
 }
 
-struct i915_error_state_file_priv {
-	struct drm_device *dev;
-	struct drm_i915_error_state *error;
-};
-
-
-static int i915_error_state(struct i915_error_state_file_priv *error_priv,
-			    struct drm_i915_error_state_buf *m)
-
+int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
+			    const struct i915_error_state_file_priv *error_priv)
 {
 	struct drm_device *dev = error_priv->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
@@ -848,7 +841,7 @@ static int i915_error_state(struct i915_error_state_file_priv *error_priv,
 
 	if (!error) {
 		err_printf(m, "no error state collected\n");
-		return 0;
+		goto out;
 	}
 
 	err_printf(m, "Time: %ld s %ld us\n", error->time.tv_sec,
@@ -958,6 +951,10 @@ static int i915_error_state(struct i915_error_state_file_priv *error_priv,
 	if (error->display)
 		intel_display_print_error_state(m, dev, error->display);
 
+out:
+	if (m->bytes == 0 && m->err)
+		return m->err;
+
 	return 0;
 }
 
@@ -1051,15 +1048,10 @@ static ssize_t i915_error_state_read(struct file *file, char __user *userbuf,
 
 	error_str.start = *pos;
 
-	ret = i915_error_state(error_priv, &error_str);
+	ret = i915_error_state_to_str(&error_str, error_priv);
 	if (ret)
 		goto out;
 
-	if (error_str.bytes == 0 && error_str.err) {
-		ret = error_str.err;
-		goto out;
-	}
-
 	ret_count = simple_read_from_buffer(userbuf, count, &tmp_pos,
 					    error_str.buf,
 					    error_str.bytes);

drivers/gpu/drm/i915/i915_drv.h

@@ -916,6 +916,11 @@ struct drm_i915_error_state_buf {
 	loff_t pos;
 };
 
+struct i915_error_state_file_priv {
+	struct drm_device *dev;
+	struct drm_i915_error_state *error;
+};
+
 struct i915_gpu_error {
 	/* For hangcheck timer */
 #define DRM_I915_HANGCHECK_PERIOD 1500 /* in ms */
@@ -1921,6 +1926,8 @@ int i915_debugfs_init(struct drm_minor *minor);
 void i915_debugfs_cleanup(struct drm_minor *minor);
 __printf(2, 3)
 void i915_error_printf(struct drm_i915_error_state_buf *e, const char *f, ...);
+int i915_error_state_to_str(struct drm_i915_error_state_buf *estr,
+			    const struct i915_error_state_file_priv *error);
 
 /* i915_suspend.c */
 extern int i915_save_state(struct drm_device *dev);