1 files changed, 98 insertions, 0 deletions
diff --git a/util/nvmutil/lib/word.c b/util/nvmutil/lib/word.c
new file mode 100644
index 00000000..4a8280ba
--- /dev/null
+++ b/util/nvmutil/lib/word.c
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (c) 2022-2026 Leah Rowe <leah@libreboot.org>
+ *
+ * Manipulate sixteen-bit little-endian
+ * words on Intel GbE NVM configurations.
+ */
+
+#ifdef __OpenBSD__
+#include <sys/param.h>
+#endif
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "../include/common.h"
+
+/*
+ * GbE NVM files store 16-bit (2-byte) little-endian words.
+ * We must therefore swap the order when reading or writing.
+ *
+ * NOTE: The MAC address words are stored big-endian in the
+ * file, but we assume otherwise and adapt accordingly.
+ */
+
+unsigned short
+nvm_word(unsigned long pos16, unsigned long p)
+{
+	struct xstate *x = xstatus();
+	struct xfile *f;
+
+	unsigned long pos;
+
+	f = &x->f;
+
+	check_nvm_bound(pos16, p);
+	pos = (pos16 << 1) + (p * GBE_PART_SIZE);
+
+	return (unsigned short)f->buf[pos] |
+	    ((unsigned short)f->buf[pos + 1] << 8);
+}
+
+void
+set_nvm_word(unsigned long pos16, unsigned long p, unsigned short val16)
+{
+	struct xstate *x = xstatus();
+	struct xfile *f;
+
+	unsigned long pos;
+
+	f = &x->f;
+
+	check_nvm_bound(pos16, p);
+	pos = (pos16 << 1) + (p * GBE_PART_SIZE);
+
+	f->buf[pos] = (unsigned char)(val16 & 0xff);
+	f->buf[pos + 1] = (unsigned char)(val16 >> 8);
+
+	set_part_modified(p);
+}
+
+void
+set_part_modified(unsigned long p)
+{
+	struct xstate *x = xstatus();
+	struct xfile *f;
+
+	f = &x->f;
+
+	check_bin(p, "part number");
+	f->part_modified[p] = 1;
+}
+
+void
+check_nvm_bound(unsigned long c, unsigned long p)
+{
+	/*
+	 * NVM_SIZE assumed as the limit, because this
+	 * current design assumes that we will only
+	 * ever modified the NVM area.
+	 */
+
+	check_bin(p, "part number");
+
+	if (c >= NVM_WORDS)
+		err(ECANCELED, "check_nvm_bound: out of bounds %lu",
+		    (unsigned long)c);
+}