[PATCH v7 2/5] drm/atomic: Add error_code element in atomic_state

[Arun R Murthy]

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
v6: Replace drm_err with drm_dbg_atomic print
v6: Add keyword "commit failed" in dbg msg (Suraj)

Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
---
 drivers/gpu/drm/drm_atomic.c | 31 +++++++++++++++++++++++++++++++
 include/drm/drm_atomic.h     | 10 ++++++++++
 2 files changed, 41 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 
52738b80ddbeb124896f6124df5628e2ac27faa4..0f4f6071cc305a114654c6973272bbc4b1ff36c8
 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -2105,6 +2105,37 @@ 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_dbg_atomic(state->dev, "Commit failed: %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 
178f8f62c80fc58fe42e8564a716da1a99ddb7da..b080f981ec1afd4b2569aba703c93fc1ea582cbf
 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -633,6 +633,13 @@ 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);
@@ -1360,5 +1367,8 @@ 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