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

Arun R Murthy
2026-02-23T09:17:59Z

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