lib: add region file support

The region file library is added to provide the underpinnings for
other libraries that support appending updates when the data changes.
The most recent written data is deemed the latest data associated
with that "file". A good example is the MRC cache which in a follow-up
patch utilizes this library.

BUG=chrome-os-partner:56151

Change-Id: Ic3caf1edbb6f11dbbe27181a87b7b19d1224fffa
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17713
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/src/include/region_file.h b/src/include/region_file.h
new file mode 100644
index 0000000000..0b79be3687
--- /dev/null
+++ b/src/include/region_file.h
@@ -0,0 +1,62 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef REGION_FILE_H
+#define REGION_FILE_H
+
+#include <commonlib/region.h>
+#include <stdint.h>
+
+/*
+ * A region file is an abstraction to allow appending updates in a
+ * region_device where the data returned is the most recently written
+ * data. It is block based with a 16 byte granularity. So if you write
+ * 2 bytes into the file the data returned in the region_device would
+ * have 16 bytes allocated for the latest update. Additionally, the
+ * current maximum file size allowed is 1MiB - 48 bytes. See comments
+ * in C implementation file for further details.
+ */
+
+struct region_file;
+
+/*
+ * Initialize a region file associated with a provided region device.
+ * Returns < 0 on error, 0 on success.
+ */
+int region_file_init(struct region_file *f, const struct region_device *p);
+
+/*
+ * Initialize region device object associated with latest update of file data.
+ * Returns < 0 on error, 0 on success.
+ */
+int region_file_data(const struct region_file *f, struct region_device *rdev);
+
+/* Update region file with latest data. Returns < 0 on error, 0 on success. */
+int region_file_update_data(struct region_file *f, const void *buf,
+				size_t size);
+
+/* Declared here for easy object allocation. */
+struct region_file {
+	/* Region device covering file */
+	struct region_device rdev;
+	/* Metadata containing blocks of the data stream. */
+	struct region_device metadata;
+	/* Blocks forming data. */
+	uint16_t data_blocks[2];
+	/* Current slot in metadata marking end of data. */
+	int slot;
+};
+
+#endif /* REGION_FILE_H */