lib/fmap: Add area read/write functions

Change-Id: I7669b8dc07b1aa5f00e7d8d0b1305b3de6c5949c
Signed-off-by: T Michael Turney <mturney@codeaurora.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32287
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/fmap.h

@@ -40,4 +40,12 @@ int fmap_locate_area(const char *name, struct region *r);
  * Return 0 on success, < 0 on error. */
 int fmap_find_region_name(const struct region * const ar,
 	char name[FMAP_STRLEN]);
+
+/* Read fmap area into provided buffer.
+ * Return size read on success, < 0 on error. */
+ssize_t fmap_read_area(const char *name, void *buffer, size_t size);
+
+/* Write provided buffer into fmap area.
+ * Return size written on success, < 0 on error. */
+ssize_t fmap_overwrite_area(const char *name, const void *buffer, size_t size);
 #endif

src/lib/fmap.c

@@ -173,3 +173,25 @@ int fmap_find_region_name(const struct region * const ar,
 
 	return -1;
 }
+
+ssize_t fmap_read_area(const char *name, void *buffer, size_t size)
+{
+	struct region_device rdev;
+	if (fmap_locate_area_as_rdev(name, &rdev))
+		return -1;
+	return rdev_readat(&rdev, buffer, 0,
+			MIN(size, region_device_sz(&rdev)));
+}
+
+ssize_t fmap_overwrite_area(const char *name, const void *buffer, size_t size)
+{
+	struct region_device rdev;
+
+	if (fmap_locate_area_as_rdev_rw(name, &rdev))
+		return -1;
+	if (size > region_device_sz(&rdev))
+		return -1;
+	if (rdev_eraseat(&rdev, 0, region_device_sz(&rdev)) < 0)
+		return -1;
+	return rdev_writeat(&rdev, buffer, 0, size);
+}