firmware: Google VPD: import lib_vpd source files

This patch imports lib_vpd.h and vpd_decode.c from the Chromium Vital
Product Data project.

This library is used to parse VPD sections obtained from coreboot table
entries describing Chromebook devices product data. Only the sections of
type VPD_TYPE_STRING are decoded.

The VPD string sections in the coreboot tables contain the type (1 byte
set to 0x01 for strings), the key length, the key ascii array, the value
length, and the value ascii array. The key and value arrays are not null
terminated.
Signed-off-by: Wei-Ning Huang <wnhuang@google.com>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/google/vpd_decode.c

+/*
+ * vpd_decode.c
+ *
+ * Google VPD decoding routines.
+ *
+ * Copyright 2017 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2.0 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/export.h>
+
+#include "vpd_decode.h"
+
+static int vpd_decode_len(const s32 max_len, const u8 *in,
+			  s32 *length, s32 *decoded_len)
+{
+	u8 more;
+	int i = 0;
+
+	if (!length || !decoded_len)
+		return VPD_FAIL;
+
+	*length = 0;
+	do {
+		if (i >= max_len)
+			return VPD_FAIL;
+
+		more = in[i] & 0x80;
+		*length <<= 7;
+		*length |= in[i] & 0x7f;
+		++i;
+	} while (more);
+
+	*decoded_len = i;
+
+	return VPD_OK;
+}
+
+int vpd_decode_string(const s32 max_len, const u8 *input_buf, s32 *consumed,
+		      vpd_decode_callback callback, void *callback_arg)
+{
+	int type;
+	int res;
+	s32 key_len;
+	s32 value_len;
+	s32 decoded_len;
+	const u8 *key;
+	const u8 *value;
+
+	/* type */
+	if (*consumed >= max_len)
+		return VPD_FAIL;
+
+	type = input_buf[*consumed];
+
+	switch (type) {
+	case VPD_TYPE_INFO:
+	case VPD_TYPE_STRING:
+		(*consumed)++;
+
+		/* key */
+		res = vpd_decode_len(max_len - *consumed, &input_buf[*consumed],
+				     &key_len, &decoded_len);
+		if (res != VPD_OK || *consumed + decoded_len >= max_len)
+			return VPD_FAIL;
+
+		*consumed += decoded_len;
+		key = &input_buf[*consumed];
+		*consumed += key_len;
+
+		/* value */
+		res = vpd_decode_len(max_len - *consumed, &input_buf[*consumed],
+				     &value_len, &decoded_len);
+		if (res != VPD_OK || *consumed + decoded_len > max_len)
+			return VPD_FAIL;
+
+		*consumed += decoded_len;
+		value = &input_buf[*consumed];
+		*consumed += value_len;
+
+		if (type == VPD_TYPE_STRING)
+			return callback(key, key_len, value, value_len,
+					callback_arg);
+		break;
+
+	default:
+		return VPD_FAIL;
+	}
+
+	return VPD_OK;
+}

drivers/firmware/google/vpd_decode.h

+/*
+ * vpd_decode.h
+ *
+ * Google VPD decoding routines.
+ *
+ * Copyright 2017 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2.0 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __VPD_DECODE_H
+#define __VPD_DECODE_H
+
+#include <linux/types.h>
+
+enum {
+	VPD_OK = 0,
+	VPD_FAIL,
+};
+
+enum {
+	VPD_TYPE_TERMINATOR = 0,
+	VPD_TYPE_STRING,
+	VPD_TYPE_INFO                = 0xfe,
+	VPD_TYPE_IMPLICIT_TERMINATOR = 0xff,
+};
+
+/* Callback for vpd_decode_string to invoke. */
+typedef int vpd_decode_callback(const u8 *key, s32 key_len,
+				const u8 *value, s32 value_len,
+				void *arg);
+
+/*
+ * vpd_decode_string
+ *
+ * Given the encoded string, this function invokes callback with extracted
+ * (key, value). The *consumed will be plused the number of bytes consumed in
+ * this function.
+ *
+ * The input_buf points to the first byte of the input buffer.
+ *
+ * The *consumed starts from 0, which is actually the next byte to be decoded.
+ * It can be non-zero to be used in multiple calls.
+ *
+ * If one entry is successfully decoded, sends it to callback and returns the
+ * result.
+ */
+int vpd_decode_string(const s32 max_len, const u8 *input_buf, s32 *consumed,
+		      vpd_decode_callback callback, void *callback_arg);
+
+#endif  /* __VPD_DECODE_H */