drm/i915: Avoid oops when capturing NULL ring for inactive pinned buffers

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -572,9 +572,9 @@ static int i915_ringbuffer_info(struct seq_file *m, void *data)
 static const char *ring_str(int ring)
 {
 	switch (ring) {
-	case RING_RENDER: return "render";
-	case RING_BSD: return "bsd";
-	case RING_BLT: return "blt";
+	case RING_RENDER: return " render";
+	case RING_BSD: return " bsd";
+	case RING_BLT: return " blt";
 	default: return "";
 	}
 }

drivers/gpu/drm/i915/i915_irq.c

@@ -575,7 +575,7 @@ static u32 capture_bo_list(struct drm_i915_error_buffer *err,
 		err->tiling = obj->tiling_mode;
 		err->dirty = obj->dirty;
 		err->purgeable = obj->madv != I915_MADV_WILLNEED;
-		err->ring = obj->ring->id;
+		err->ring = obj->ring ? obj->ring->id : 0;
 
 		if (++i == count)
 			break;