[PATCH v3 3/4] 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.

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
---
 drivers/gpu/drm/drm_atomic.c      |  6 ++++
 drivers/gpu/drm/drm_atomic_uapi.c | 60 ++++++++++++++++++++++++++++++++-------
 2 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index cd15cf52f0c9144711da5879da57884674aea9e4..5f25e6d3cf6cf246f83a8c39450b410e97fe45bb 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1513,6 +1513,9 @@ 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->failure_flags =
+					DRM_MODE_ATOMIC_CRTC_NEED_FULL_MODESET;
+
 				return -EINVAL;
 			}
 		}
@@ -1537,8 +1540,11 @@ 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->failure_flags = 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..94eaf9c98eb4ac2455799f1416010d366e1b5bbc 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1058,6 +1058,9 @@ 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->failure_flags =
+					DRM_MODE_ATOMIC_ASYNC_PROP_CHANGED;
 			break;
 		}
 
@@ -1089,6 +1092,8 @@ 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->failure_flags =
+					DRM_MODE_ATOMIC_ASYNC_NOT_SUP_PLANE;
 				ret = -EINVAL;
 
 				if (plane_funcs && plane_funcs->atomic_async_check)
@@ -1380,6 +1385,13 @@ set_async_flip(struct drm_atomic_state *state)
 	}
 }
 
+#define FAILURE_REASON(flag, reason) #reason,
+const char *drm_mode_atomic_failure_string[] = {
+	DRM_MODE_ATOMIC_FAILURE_REASON
+};
+
+#undef FAILURE_REASON
+
 int drm_mode_atomic_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv)
 {
@@ -1389,9 +1401,11 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	uint32_t __user *props_ptr = (uint32_t __user *)(unsigned long)(arg->props_ptr);
 	uint64_t __user *prop_values_ptr = (uint64_t __user *)(unsigned long)(arg->prop_values_ptr);
 	unsigned int copied_objs, copied_props;
-	struct drm_atomic_state *state;
+	struct drm_atomic_state *state = NULL;
 	struct drm_modeset_acquire_ctx ctx;
 	struct drm_out_fence_state *fence_state;
+	struct drm_mode_atomic_err_code error_code;
+	struct drm_mode_atomic_err_code __user *error_code_ptr;
 	int ret = 0;
 	unsigned int i, j, num_fences;
 	bool async_flip = false;
@@ -1400,6 +1414,11 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
 		return -EOPNOTSUPP;
 
+	if (!arg->reserved)
+		drm_err(dev, "memory not allocated for drm_atomic error reporting\n");
+
+	memset(&error_code, 0, sizeof(struct drm_mode_atomic_err_code));
+
 	/* 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)
@@ -1407,24 +1426,25 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (!file_priv->atomic) {
 		drm_dbg_atomic(dev,
 			       "commit failed: atomic cap not enabled\n");
-		return -EINVAL;
+		error_code.failure_flags = DRM_MODE_ATOMIC_CAP_NOT_ENABLED;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	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");
-		return -EINVAL;
+		error_code.failure_flags = DRM_MODE_ATOMIC_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");
-			return -EINVAL;
+			error_code.failure_flags = DRM_MODE_ATOMIC_PAGE_FLIP_ASYNC;
+			ret = -EINVAL;
+			goto out;
 		}
 
 		async_flip = true;
@@ -1435,7 +1455,9 @@ 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");
-		return -EINVAL;
+		error_code.failure_flags = DRM_MODE_ATOMIC_FLIP_EVENT_WITH_CHECKONLY;
+		ret = -EINVAL;
+		goto out;
 	}
 
 	state = drm_atomic_state_alloc(dev);
@@ -1446,6 +1468,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	state->acquire_ctx = &ctx;
 	state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET);
 
+	state->error_code = &error_code;
+
 retry:
 	copied_objs = 0;
 	copied_props = 0;
@@ -1542,6 +1566,22 @@ 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) {
+		error_code_ptr = (struct drm_mode_atomic_err_code __user *)
+				 (unsigned long)arg->reserved;
+
+		strscpy_pad(error_code.failure_string,
+			    drm_mode_atomic_failure_string[error_code.failure_flags],
+			    sizeof(error_code.failure_string));
+
+		if (copy_to_user(error_code_ptr, &error_code, sizeof(error_code)))
+			return -EFAULT;
+	}
+
+	if (!state)
+		return ret;
+
 	complete_signaling(dev, state, fence_state, num_fences, !ret);
 
 	if (ret == -EDEADLK) {

-- 
2.25.1