efi: Move key decoding into a shared file

Create a new file in lib/efi to handle conversion of keys from EFI
format to characters, so we can use it from multiple places. Update the
serial_efi driver accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>

lib/efi/Makefile

@@ -6,6 +6,7 @@
 obj-y += basename.o
 obj-y += device_path.o
 obj-y += helper.o
+obj-y += input.o
 obj-y += load_options.o
 obj-y += memory.o
 obj-y += run.o

lib/efi/input.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * EFI input key decoding functions
+ *
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#define LOG_CATEGORY	LOGC_EFI
+
+#include <efi.h>
+#include <efi_api.h>
+#include <cli.h>
+
+int efi_decode_key(struct efi_input_key *key)
+{
+	static const char conv_scan[] = {0, 'p', 'n', 'f', 'b', 'a', 'e', 0, 8};
+	int ch;
+
+	ch = key->unicode_char;
+
+	/*
+	 * Unicode char 8 (for backspace) is never returned. Instead we get a
+	 * key scan code of 8. Handle this so that backspace works correctly
+	 * in the U-Boot command line.
+	 */
+	if (!ch && key->scan_code < sizeof(conv_scan)) {
+		ch = conv_scan[key->scan_code];
+		if (ch >= 'a')
+			ch -= 'a' - 1;
+	}
+	log_debug(" [%x %x %x] ", ch, key->unicode_char, key->scan_code);
+
+	return ch;
+}
+
+int efi_decode_key_ex(struct efi_key_data *key_data)
+{
+	return efi_decode_key(&key_data->key);
+}