drm/i915: add GETPARAM request for page flipping

Add a GETPARAM request for checking if page flipping is supported.
Useful for the 2D driver to enable the flipping path.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index a8efe78..fe89d0c 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -810,6 +810,9 @@
 	case I915_PARAM_HAS_OVERLAY:
 		value = dev_priv->overlay ? 1 : 0;
 		break;
+	case I915_PARAM_HAS_PAGEFLIPPING:
+		value = 1;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Unknown parameter %d\n",
 					param->param);