[PATCH v5 2/5] drm/atomic: Add error_code element in atomic_state

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

Now that a proper error code will be returned to the user on any failure
in atomic_ioctl() via struct drm_mode_atomic, add a new element
error_code in the struct drm_atomic_state so as to hold the error code
during the atomic_check() and atomic_commit() phases.
New function added to print the error message and fill the struct
err_code with proper error message and error code.

v5: Add a function for printing the error message and filling err_code
    struct

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
---
 drivers/gpu/drm/drm_atomic.c | 34 ++++++++++++++++++++++++++++++++--
 include/drm/drm_atomic.h     | 10 ++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index cd15cf52f0c9144711da5879da57884674aea9e4..86d1d14a3f434c48028598d7dfe8e651b2de0305 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1511,9 +1511,8 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 	if (!state->allow_modeset) {
 		for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
 			if (drm_atomic_crtc_needs_modeset(new_crtc_state)) {
-				drm_dbg_atomic(dev, "[CRTC:%d:%s] requires full modeset\n",
+				drm_dbg_atomic(dev, "[CRTC:%d:%s] requires full modese\n",
 					       crtc->base.id, crtc->name);
-				return -EINVAL;
 			}
 		}
 	}
@@ -1897,6 +1896,37 @@ void drm_state_dump(struct drm_device *dev, struct drm_printer *p)
 }
 EXPORT_SYMBOL(drm_state_dump);
 
+/**
+ * drm_mode_atomic_add_error_msg - function to add error code and error string
+ *
+ * @err_code: pointer to struct drm_mode_atomic_err_code that stores the failure
+ *	      reason
+ * @failure_code: failure code in enum drm_mode_atomic_failure_codes
+ * @failure_string: failure reason string message
+ *
+ * Returns: void
+ */
+void drm_mode_atomic_add_error_msg(struct drm_mode_atomic_err_code *err_code,
+				   __u64 failure_code, const char *format, ...)
+{
+	struct drm_atomic_state *state = container_of(err_code,
+						      struct drm_atomic_state,
+						      error_code);
+	va_list varg;
+	char *failure_string;
+
+	err_code->failure_code = failure_code;
+
+	va_start(varg, format);
+	failure_string = kvasprintf(GFP_ATOMIC, format, varg);
+
+	drm_err(state->dev, "%s\n", failure_string);
+	strscpy_pad(err_code->failure_string, failure_string,
+		    sizeof(err_code->failure_string));
+	va_end(varg);
+}
+EXPORT_SYMBOL(drm_mode_atomic_add_error_msg);
+
 #ifdef CONFIG_DEBUG_FS
 static int drm_state_info(struct seq_file *m, void *data)
 {
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 38636a593c9d98cadda85ccd67326cb152f0dd27..ab04cffc9d03d70a791fe3eaaa7f1efea39b600a 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -524,6 +524,13 @@ struct drm_atomic_state {
 	 * commit without blocking.
 	 */
 	struct work_struct commit_work;
+
+	/* @error_code: pointer to struct holding failure reason and string
+	 *
+	 * struct to convey user readable error to the user.
+	 * Error codes defined in enum drm_mode_atomic_failure_flags
+	 */
+	struct drm_mode_atomic_err_code error_code;
 };
 
 void __drm_crtc_commit_free(struct kref *kref);
@@ -1247,5 +1254,8 @@ drm_atomic_get_old_bridge_state(const struct drm_atomic_state *state,
 struct drm_bridge_state *
 drm_atomic_get_new_bridge_state(const struct drm_atomic_state *state,
 				struct drm_bridge *bridge);
+__printf(3, 4)
+void drm_mode_atomic_add_error_msg(struct drm_mode_atomic_err_code *err_code,
+				   __u64 failure_code, const char *format, ...);
 
 #endif /* DRM_ATOMIC_H_ */

-- 
2.25.1