Add crc8 routine

Add an implementation of the CRC8 algorithm. This is required by the TPM
emulation, but is probably useful to U-Boot in general.

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

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

include/linux/crc8.h

+/*
+ * Copyright (c) 2013 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+
+#ifndef __linux_crc8_h
+#define __linux_crc8_h
+
+/**
+ * crc8() - Calculate and return CRC-8 of the data
+ *
+ * This uses an x^8 + x^2 + x + 1 polynomial.  A table-based algorithm would
+ * be faster, but for only a few bytes it isn't worth the code size
+ *
+ * @vptr: Buffer to checksum
+ * @len: Length of buffer in bytes
+ * @return CRC8 checksum
+ */
+unsigned int crc8(const unsigned char *vptr, int len);
+
+#endif

lib/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_BZIP2) += bzlib_randtable.o
 obj-$(CONFIG_BZIP2) += bzlib_huffman.o
 obj-$(CONFIG_USB_TTY) += circbuf.o
 obj-y += crc7.o
+obj-y += crc8.o
 obj-y += crc16.o
 obj-$(CONFIG_OF_CONTROL) += fdtdec.o
 obj-$(CONFIG_TEST_FDTDEC) += fdtdec_test.o

lib/crc8.c

+/*
+ * Copyright (c) 2013 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "linux/crc8.h"
+
+unsigned int crc8(const unsigned char *vptr, int len)
+{
+	const unsigned char *data = vptr;
+	unsigned int crc = 0;
+	int i, j;
+
+	for (j = len; j; j--, data++) {
+		crc ^= (*data << 8);
+		for (i = 8; i; i--) {
+			if (crc & 0x8000)
+				crc ^= (0x1070 << 3);
+			crc <<= 1;
+		}
+	}
+
+	return (crc >> 8) & 0xff;
+}