[PATCH v10 5/7] drm/atomic: Return user readable error in atomic_ioctl

[Arun R Murthy <arun.r.murthy@intel.com>]

Add user readable error codes for failure cases in drm_atomic_ioctl() so
that user can decode the error code and take corrective measurements.

v8: Replaced DRM_MODE_ATOMIC_ASYNC_NOT_SUPP_PLANE,
    DRM_MODE_ATOMIC_ASYNC_MODIFIER_NOT_SUPP with INVALID_API_USAGE
    (Xaver)
v9: Move free atomic_state on error to patch 3 (Suraj)
v10: on copy_to_user error free atomic_state and drop acquired locks
(Suraj)

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/drm_atomic_uapi.c | 58 +++++++++++++++++++++++++++++----------
 1 file changed, 44 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index f295a397c26c24c6414a25bacff051bd694260c5..0a4a8e8033d21a78efaeda0dca3e018dc3ae542a 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1196,6 +1196,11 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 			ret = drm_atomic_connector_get_property(connector, connector_state,
 								prop, &old_val);
 			ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
+			if (ret) {
+				drm_mode_atomic_add_error_msg(&state->error_code,
+							      DRM_MODE_ATOMIC_ASYNC_PROP_CHANGED,
+							      "property change not allowed in async flip");
+			}
 			break;
 		}
 
@@ -1218,6 +1223,11 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 			ret = drm_atomic_crtc_get_property(crtc, crtc_state,
 							   prop, &old_val);
 			ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
+			if (ret) {
+				drm_mode_atomic_add_error_msg(&state->error_code,
+							      DRM_MODE_ATOMIC_ASYNC_PROP_CHANGED,
+							      "property change not allowed in async flip");
+			}
 			break;
 		}
 
@@ -1256,9 +1266,10 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 					ret = plane_funcs->atomic_async_check(plane, state, true);
 
 				if (ret) {
-					drm_dbg_atomic(prop->dev,
-						       "[PLANE:%d:%s] does not support async flips\n",
-						       obj->id, plane->name);
+					drm_mode_atomic_add_error_msg(&state->error_code,
+								      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+								      "[PLANE:%d:%s] does not support async flip",
+								      obj->id, plane->name);
 					break;
 				}
 			}
@@ -1568,6 +1579,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	struct drm_atomic_state *state;
 	struct drm_modeset_acquire_ctx ctx;
 	struct drm_out_fence_state *fence_state;
+	struct drm_mode_atomic_err_code __user *error_code_ptr;
 	int ret = 0;
 	unsigned int i, j, num_fences = 0;
 	bool async_flip = false;
@@ -1576,6 +1588,14 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
 		return -EOPNOTSUPP;
 
+	if (!arg->reserved)
+		drm_dbg_atomic(dev,
+			       "memory not allocated for drm_atomic error reporting\n");
+	else
+		/* Update the error code if any error to allow user handling it */
+		error_code_ptr = (struct drm_mode_atomic_err_code __user *)
+				 (unsigned long)arg->reserved;
+
 	state = drm_atomic_state_alloc(dev);
 	if (!state)
 		return -ENOMEM;
@@ -1584,11 +1604,16 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	state->acquire_ctx = &ctx;
 	state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET);
 
+	memset(&state->error_code, 0, sizeof(*error_code_ptr));
+
 	/* disallow for userspace that has not enabled atomic cap (even
 	 * though this may be a bit overkill, since legacy userspace
 	 * wouldn't know how to call this ioctl)
 	 */
 	if (!file_priv->atomic) {
+		drm_mode_atomic_add_error_msg(&state->error_code,
+					      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+					      "drm atomic capability not enabled");
 		drm_dbg_atomic(dev,
 			       "commit failed: atomic cap not enabled\n");
 		ret = -EINVAL;
@@ -1596,21 +1621,18 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	}
 
 	if (arg->flags & ~DRM_MODE_ATOMIC_FLAGS) {
-		drm_dbg_atomic(dev, "commit failed: invalid flag\n");
-		ret = -EINVAL;
-		goto out;
-	}
-
-	if (arg->reserved) {
-		drm_dbg_atomic(dev, "commit failed: reserved field set\n");
+		drm_mode_atomic_add_error_msg(&state->error_code,
+					      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+					      "invalid flag");
 		ret = -EINVAL;
 		goto out;
 	}
 
 	if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC) {
 		if (!dev->mode_config.async_page_flip) {
-			drm_dbg_atomic(dev,
-				       "commit failed: DRM_MODE_PAGE_FLIP_ASYNC not supported\n");
+			drm_mode_atomic_add_error_msg(&state->error_code,
+						      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+						      "DRM_MODE_PAGE_FLIP_ASYNC not supported with ATOMIC ioctl");
 			ret = -EINVAL;
 			goto out;
 		}
@@ -1621,8 +1643,9 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	/* can't test and expect an event at the same time. */
 	if ((arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) &&
 			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT)) {
-		drm_dbg_atomic(dev,
-			       "commit failed: page-flip event requested with test-only commit\n");
+		drm_mode_atomic_add_error_msg(&state->error_code,
+					      DRM_MODE_ATOMIC_INVALID_API_USAGE,
+					      "page-flip event requested with test-only commit");
 		ret = -EINVAL;
 		goto out;
 	}
@@ -1725,6 +1748,13 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	}
 
 out:
+	/* Update the error code if any error to allow user handling it */
+	if (ret < 0 && arg->reserved) {
+		if (copy_to_user(error_code_ptr, &state->error_code,
+				 sizeof(state->error_code)))
+			ret = -EFAULT;
+	}
+
 	if (num_fences)
 		complete_signaling(dev, state, fence_state, num_fences, !ret);
 

-- 
2.25.1