efi_loader: fix text output for Uart() DP nodes

The UEFI specification concerning Uart() device path nodes has been
clarified:

Parity and stop bits can either both use keywords or both use
numbers but numbers and keywords should not be mixed.

Let's go for keywords as this is what EDK II does. For illegal
values fall back to numbers.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

diff --git a/lib/efi_loader/efi_device_path_to_text.c b/lib/efi_loader/efi_device_path_to_text.c
index 97b3d3e815ea93cef8bdb77640b8bee5005084ce..4d73954ef89e8568c4e7cf5ce9f2eb0b3d92467e 100644 (file)
--- a/lib/efi_loader/efi_device_path_to_text.c
+++ b/lib/efi_loader/efi_device_path_to_text.c
@@ -122,16 +122,26 @@ static char *dp_msging(char *s, struct efi_device_path *dp)
        case DEVICE_PATH_SUB_TYPE_MSG_UART: {
                struct efi_device_path_uart *uart =
                        (struct efi_device_path_uart *)dp;
-               s += sprintf(s, "Uart(%lld,%d,%d,", uart->baud_rate,
-                            uart->data_bits, uart->parity);
-               switch (uart->stop_bits) {
-               case 2:
-                       s += sprintf(s, "1.5)");
-                       break;
-               default:
+               const char parity_str[6] = {'D', 'N', 'E', 'O', 'M', 'S'};
+               const char *stop_bits_str[4] = { "D", "1", "1.5", "2" };
+
+               s += sprintf(s, "Uart(%lld,%d,", uart->baud_rate,
+                            uart->data_bits);
+
+               /*
+                * Parity and stop bits can either both use keywords or both use
+                * numbers but numbers and keywords should not be mixed. Let's
+                * go for keywords as this is what EDK II does. For illegal
+                * values fall back to numbers.
+                */
+               if (uart->parity < 6)
+                       s += sprintf(s, "%c,", parity_str[uart->parity]);
+               else
+                       s += sprintf(s, "%d,", uart->parity);
+               if (uart->stop_bits < 4)
+                       s += sprintf(s, "%s)", stop_bits_str[uart->stop_bits]);
+               else
                        s += sprintf(s, "%d)", uart->stop_bits);
-                       break;
-               }
                break;
        }
        case DEVICE_PATH_SUB_TYPE_MSG_USB: {