Claude review: drm/atomic: Add error_code element in atomic_state

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Issues:**

```c
+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);
```
- **Questionable Design**: Using `container_of` to get back to `drm_atomic_state` is fragile. Why not pass `state` directly?

```c
+	va_list varg;
+	char *failure_string;
+
+	err_code->failure_code = failure_code;
+
+	va_start(varg, format);
+	failure_string = kvasprintf(GFP_ATOMIC, format, varg);
```
- **Memory Leak**: `failure_string` is allocated with `kvasprintf` but never freed
- **NULL Check Missing**: `kvasprintf` can return NULL, not checked before use
- **GFP_ATOMIC**: Why GFP_ATOMIC? The ioctl path should allow GFP_KERNEL

```c
+	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);
+}
```
- **Use After Free Potential**: If `failure_string` is NULL (allocation failed), this crashes
- **Missing kfree**: Memory leak confirmed

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Generated by Claude Code Patch Reviewer