ihex.h: binary representation of ihex records

Some devices need their firmware as a set of {address, len, data...}
records in some specific order rather than a simple blob.

The normal way of doing this kind of thing is 'ihex', which is a text
format and not entirely suitable for use in the kernel.

This provides a binary representation which is very similar, but much
more compact -- and a helper routine to skip to the next record,
because the alignment constraints mean that everybody will screw it up
for themselves otherwise.

Also a helper function which can verify that a 'struct firmware'
contains a valid set of ihex records, and that following them won't run
off the end of the loaded data.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

include/linux/ihex.h

+/*
+ * Compact binary representation of ihex records. Some devices need their
+ * firmware loaded in strange orders rather than a single big blob, but
+ * actually parsing ihex-as-text within the kernel seems silly. Thus,...
+ */
+
+#ifndef __LINUX_IHEX_H__
+#define __LINUX_IHEX_H__
+
+#include <linux/types.h>
+#include <linux/firmware.h>
+
+/* Intel HEX files actually limit the length to 256 bytes, but we have
+   drivers which would benefit from using separate records which are
+   longer than that, so we extend to 16 bits of length */
+struct ihex_binrec {
+	__be32 addr;
+	__be16 len;
+	uint8_t data[0];
+} __attribute__((aligned(4)));
+
+/* Find the next record, taking into account the 4-byte alignment */
+static inline const struct ihex_binrec *
+ihex_next_binrec(const struct ihex_binrec *rec)
+{
+	int next = ((be16_to_cpu(rec->len) + 5) & ~3) - 2;
+	rec = (void *)&rec->data[next];
+
+	return be16_to_cpu(rec->len) ? rec : NULL;
+}
+
+/* Check that ihex_next_binrec() won't take us off the end of the image... */
+static inline int ihex_validate_fw(const struct firmware *fw)
+{
+	const struct ihex_binrec *rec;
+	size_t ofs = 0;
+
+	while (ofs <= fw->size - sizeof(*rec)) {
+		rec = (void *)&fw->data[ofs];
+
+		/* Zero length marks end of records */
+		if (!be16_to_cpu(rec->len))
+			return 0;
+
+		/* Point to next record... */
+		ofs += (sizeof(*rec) + be16_to_cpu(rec->len) + 3) & ~3;
+	}
+	return -EINVAL;
+}
+#endif /* __LINUX_IHEX_H__ */