[PATCH v2 3/4] drm/atomic: Return user readable error in atomic_ioctl

[Arun R Murthy]

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

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/drm_atomic.c      |  5 +++++
 drivers/gpu/drm/drm_atomic_uapi.c | 20 +++++++++++++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index cd15cf52f0c9144711da5879da57884674aea9e4..0cf73022955437260d138c6a1e2bb9a8a4eca2f0 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1513,6 +1513,8 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 			if (drm_atomic_crtc_needs_modeset(new_crtc_state)) {
 				drm_dbg_atomic(dev, "[CRTC:%d:%s] requires full modeset\n",
 					       crtc->base.id, crtc->name);
+				state->error_code = DRM_MODE_ATOMIC_CRTC_NEED_FULL_MODESET;
+
 				return -EINVAL;
 			}
 		}
@@ -1537,8 +1539,11 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 		drm_dbg_atomic(dev,
 			       "driver added CRTC to commit: requested 0x%x, affected 0x%0x\n",
 			       requested_crtc, affected_crtc);
+		state->error_code = DRM_MODE_ATOMIC_NEED_FULL_MODESET;
 		WARN(!state->allow_modeset, "adding CRTC not allowed without modesets: requested 0x%x, affected 0x%0x\n",
 		     requested_crtc, affected_crtc);
+
+		return -EINVAL;
 	}
 
 	return 0;
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index ecc73d52bfae41a7ef455a7e13649ec56c690b90..b96707ca23ac01878c3df25b8a4a026f6c6c31d2 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1058,6 +1058,8 @@ 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)
+				state->error_code = DRM_MODE_ATOMIC_ASYNC_PROP_CHANGED;
 			break;
 		}
 
@@ -1089,6 +1091,7 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 
 			/* ask the driver if this non-primary plane is supported */
 			if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
+				state->error_code = DRM_MODE_ATOMIC_ASYNC_NOT_PRIMARY;
 				ret = -EINVAL;
 
 				if (plane_funcs && plane_funcs->atomic_async_check)
@@ -1400,6 +1403,11 @@ 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, "commit failed: reserved field set\n");
+		return -EINVAL;
+	}
+
 	/* 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)
@@ -1407,16 +1415,13 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (!file_priv->atomic) {
 		drm_dbg_atomic(dev,
 			       "commit failed: atomic cap not enabled\n");
+		arg->reserved = DRM_MODE_ATOMIC_CAP_NOT_ENABLED;
 		return -EINVAL;
 	}
 
 	if (arg->flags & ~DRM_MODE_ATOMIC_FLAGS) {
 		drm_dbg_atomic(dev, "commit failed: invalid flag\n");
-		return -EINVAL;
-	}
-
-	if (arg->reserved) {
-		drm_dbg_atomic(dev, "commit failed: reserved field set\n");
+		arg->reserved = DRM_MODE_ATOMIC_INVALID_FLAG;
 		return -EINVAL;
 	}
 
@@ -1424,6 +1429,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 		if (!dev->mode_config.async_page_flip) {
 			drm_dbg_atomic(dev,
 				       "commit failed: DRM_MODE_PAGE_FLIP_ASYNC not supported\n");
+			arg->reserved = DRM_MODE_ATOMIC_PAGE_FLIP_ASYNC;
 			return -EINVAL;
 		}
 
@@ -1435,6 +1441,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT)) {
 		drm_dbg_atomic(dev,
 			       "commit failed: page-flip event requested with test-only commit\n");
+		arg->reserved = DRM_MODE_ATOMIC_FLIP_EVENT_WITH_CHECKONLY;
 		return -EINVAL;
 	}
 
@@ -1541,6 +1548,9 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 		ret = drm_atomic_commit(state);
 	}
 
+	/* update the error code if any error to allow user handling it */
+	arg->reserved = state->error_code;
+
 out:
 	complete_signaling(dev, state, fence_state, num_fences, !ret);
 

-- 
2.25.1