Refine granularity handling in preparation of AT45DB series support

This adds a number of new granularitie and refines the handling of
n-byte granularities by extracting the respective code into a helper
function which reduces the pain of the above significantly.

Corresponding to flashrom svn r1666.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

flash.h

@@ -59,18 +59,22 @@ enum chipbustype {
 };
 
 /*
- * The following write granularities are known:
- * - 1 bit: Each bit can be cleared individually.
- * - 1 byte: A byte can be written once. Further writes to an already written byte cause its contents to be
- *   either undefined or to stay unchanged.
- * - 128 bytes: If less than 128 bytes are written, the rest will be erased. Each write to a 128-byte region
- *   will trigger an automatic erase before anything is written. Very uncommon behaviour.
- * - 256 bytes: If less than 256 bytes are written, the contents of the unwritten bytes are undefined.
+ * The following enum defines possible write granularities of flash chips. These tend to reflect the properties
+ * of the actual hardware not necesserily the write function(s) defined by the respective struct flashchip.
+ * The latter might (and should) be more precisely specified, e.g. they might bail out early if their execution
+ * would result in undefined chip contents.
  */
 enum write_granularity {
-	write_gran_256bytes = 0, /* We assume 256 byte granularity by default. */
-	write_gran_1bit,
-	write_gran_1byte,
+	/* We assume 256 byte granularity by default. */
+	write_gran_256bytes = 0,/* If less than 256 bytes are written, the unwritten bytes are undefined. */
+	write_gran_1bit,	/* Each bit can be cleared individually. */
+	write_gran_1byte,	/* A byte can be written once. Further writes to an already written byte cause
+				 * its contents to be either undefined or to stay unchanged. */
+	write_gran_264bytes,	/* If less than 264 bytes are written, the unwritten bytes are undefined. */
+	write_gran_512bytes,	/* If less than 512 bytes are written, the unwritten bytes are undefined. */
+	write_gran_528bytes,	/* If less than 528 bytes are written, the unwritten bytes are undefined. */
+	write_gran_1024bytes,	/* If less than 1024 bytes are written, the unwritten bytes are undefined. */
+	write_gran_1056bytes,	/* If less than 1056 bytes are written, the unwritten bytes are undefined. */
 };
 
 /*