drivers/vpd: Add VPD support

VPD reference: https://chromium.googlesource.com/chromiumos/platform/vpd/+/master/README.md

Copy ChromeOS VPD driver to add support for VPD without CROMEOS.
Possible use case:
* Storing calibration data
* Storing MAC address
* Storing serial
* Storing boot options

+ Now it's possible to define the VPD space by choosing
  one of the following enums: VPD_ANY, VPD_RW, VPD_RO.
+ CHROMEOS selects now VPD as part of it.
+ VPD is implemented as driver.

Change-Id: Id9263bd39bf25d024e93daa57053fefcb1adc53a
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/25046
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/vpd/lib_vpd.c

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ */
+#include <assert.h>
+#include "lib_vpd.h"
+
+/* Given an encoded string, this functions decodes the length field which varies
+ * from 1 byte to many bytes.
+ *
+ * The in points the actual byte going to be decoded. The *length returns
+ * the decoded length field. The number of consumed bytes will be stroed in
+ * decoded_len.
+ *
+ * Returns VPD_FAIL if more bit is 1, but actually reaches the end of string.
+ */
+int decodeLen(const int32_t max_len,
+	      const uint8_t *in,
+	      int32_t *length,
+	      int32_t *decoded_len)
+{
+	uint8_t more;
+	int i = 0;
+
+	assert(length);
+	assert(decoded_len);
+
+	*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;
+}
+
+/* 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 decodeVpdString(const int32_t max_len,
+		    const uint8_t *input_buf,
+		    int32_t *consumed,
+		    VpdDecodeCallback callback,
+		    void *callback_arg)
+{
+	int type;
+	int32_t key_len, value_len;
+	int32_t decoded_len;
+	const uint8_t *key, *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 */
+		if (VPD_OK != decodeLen(max_len - *consumed,
+					&input_buf[*consumed], &key_len,
+					&decoded_len) ||
+				*consumed + decoded_len >= max_len) {
+				return VPD_FAIL;
+		}
+
+		*consumed += decoded_len;
+		key = &input_buf[*consumed];
+		*consumed += key_len;
+
+		/* value */
+		if (VPD_OK != decodeLen(max_len - *consumed,
+					&input_buf[*consumed],
+					&value_len, &decoded_len) ||
+					*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);
+
+		return VPD_OK;
+
+	default:
+		return VPD_FAIL;
+	break;
+	}
+
+	return VPD_OK;
+}