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.mur...@intel.com>
---
 drivers/gpu/drm/drm_atomic_uapi.c | 71 ++++++++++++++++++++++++++++-----------
 1 file changed, 52 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c 
b/drivers/gpu/drm/drm_atomic_uapi.c
index 
3ef478e717bec917d1b8803c72bbcc8d6409d745..3d4e9709e8e289cf302413e171b1336812d65c1c
 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1036,6 +1036,11 @@ 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;
                }
 
@@ -1058,6 +1063,11 @@ 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;
                }
 
@@ -1096,9 +1106,10 @@ 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_ASYNC_NOT_SUPP_PLANE,
+                                                                     
"[PLANE:%d:%s] does not support async flip",
+                                                                     obj->id, 
plane->name);
                                        break;
                                }
                        }
@@ -1393,6 +1404,7 @@ 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;
@@ -1401,6 +1413,14 @@ 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;
@@ -1409,31 +1429,35 @@ 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(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)
         */
        if (!file_priv->atomic) {
-               drm_dbg_atomic(dev,
-                              "commit failed: atomic cap not enabled\n");
-               return -EINVAL;
+               drm_mode_atomic_add_error_msg(&state->error_code,
+                                             DRM_MODE_ATOMIC_INVALID_API_USAGE,
+                                             "DRM_ATOMIC capability 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;
+               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");
-                       return -EINVAL;
+                       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;
                }
 
                async_flip = true;
@@ -1442,9 +1466,11 @@ 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");
-               return -EINVAL;
+               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;
        }
 
 retry:
@@ -1543,6 +1569,13 @@ 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)))
+                       return -EFAULT;
+       }
+
        if (num_fences)
                complete_signaling(dev, state, fence_state, num_fences, !ret);
 

-- 
2.25.1

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