drm/radeon: add a way to revoke hyper-z access

Signed-off-by: Marek Olšák <maraeo@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_kms.c

@@ -162,13 +162,27 @@ int radeon_info_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 			return -EINVAL;
 		}
 	case RADEON_INFO_WANT_HYPERZ:
+		/* The "value" here is both an input and output parameter.
+		 * If the input value is 1, filp requests hyper-z access.
+		 * If the input value is 0, filp revokes its hyper-z access.
+		 *
+		 * When returning, the value is 1 if filp owns hyper-z access,
+		 * 0 otherwise. */
+		if (value >= 2) {
+			DRM_DEBUG_KMS("WANT_HYPERZ: invalid value %d\n", value);
+			return -EINVAL;
+		}
 		mutex_lock(&dev->struct_mutex);
-		if (rdev->hyperz_filp)
-			value = 0;
-		else {
-			rdev->hyperz_filp = filp;
-			value = 1;
+		if (value == 1) {
+			/* wants hyper-z */
+			if (!rdev->hyperz_filp)
+				rdev->hyperz_filp = filp;
+		} else if (value == 0) {
+			/* revokes hyper-z */
+			if (rdev->hyperz_filp == filp)
+				rdev->hyperz_filp = NULL;
 		}
+		value = rdev->hyperz_filp == filp ?  1 : 0;
 		mutex_unlock(&dev->struct_mutex);
 		break;
 	default: