+static bool __i915_error_ok(struct drm_i915_error_state_buf *e)
+{
+
+ if (!e->err && WARN(e->bytes > (e->size - 1), "overflow")) {
+ e->err = -ENOSPC;
+ return false;
+ }
+
+ if (e->bytes == e->size - 1 || e->err)
+ return false;
+
+ return true;
+}
+
+static bool __i915_error_seek(struct drm_i915_error_state_buf *e,
+ unsigned len)
+{
+ if (e->pos + len <= e->start) {
+ e->pos += len;
+ return false;
+ }
+
+ /* First vsnprintf needs to fit in its entirety for memmove */
+ if (len >= e->size) {
+ e->err = -EIO;
+ return false;
+ }
+
+ return true;
+}
+
+static void __i915_error_advance(struct drm_i915_error_state_buf *e,
+ unsigned len)
+{
+ /* If this is first printf in this window, adjust it so that
+ * start position matches start of the buffer
+ */
+
+ if (e->pos < e->start) {
+ const size_t off = e->start - e->pos;
+
+ /* Should not happen but be paranoid */
+ if (off > len || e->bytes) {
+ e->err = -EIO;
+ return;
+ }
+
+ memmove(e->buf, e->buf + off, len - off);
+ e->bytes = len - off;
+ e->pos = e->start;
+ return;
+ }
+
+ e->bytes += len;
+ e->pos += len;
+}
+
+static void i915_error_vprintf(struct drm_i915_error_state_buf *e,
+ const char *f, va_list args)
+{
+ unsigned len;
+
+ if (!__i915_error_ok(e))
+ return;
+
+ /* Seek the first printf which is hits start position */
+ if (e->pos < e->start) {
+ len = vsnprintf(NULL, 0, f, args);
+ if (!__i915_error_seek(e, len))
+ return;
+ }
+
+ len = vsnprintf(e->buf + e->bytes, e->size - e->bytes, f, args);
+ if (len >= e->size - e->bytes)
+ len = e->size - e->bytes - 1;
+
+ __i915_error_advance(e, len);
+}
+
+static void i915_error_puts(struct drm_i915_error_state_buf *e,
+ const char *str)
+{
+ unsigned len;
+
+ if (!__i915_error_ok(e))
+ return;
+
+ len = strlen(str);
+
+ /* Seek the first printf which is hits start position */
+ if (e->pos < e->start) {
+ if (!__i915_error_seek(e, len))
+ return;
+ }
+
+ if (len >= e->size - e->bytes)
+ len = e->size - e->bytes - 1;
+ memcpy(e->buf + e->bytes, str, len);
+
+ __i915_error_advance(e, len);
+}
+
+void i915_error_printf(struct drm_i915_error_state_buf *e, const char *f, ...)
+{
+ va_list args;
+
+ va_start(args, f);
+ i915_error_vprintf(e, f, args);
+ va_end(args);
+}
+
+#define err_printf(e, ...) i915_error_printf(e, __VA_ARGS__)
+#define err_puts(e, s) i915_error_puts(e, s)
+
+static void print_error_buffers(struct drm_i915_error_state_buf *m,