mtd: improve parameter parsing for block2mtd

Expand the parameter parsing for block2mtd.  It now accepts:
Ki, Mi, Gi	- the official prefixes for binary multiples,
		  see http://physics.nist.gov/cuu/Units/binary.html,
ki		- mistake on my side and analog to "k" for decimal multiples,
KiB, MiB, GiB	- for people that prefer to add a "B" for byte,
kiB		- combination of the above.

There were complaints about not accepting "k" for 1024.  This has long
been common practice, but is known to lead to confusion.  Hence the new
SI units and hence block2mtd only accepts units that cannot be confused
with decimal units.  Diverging from common practice doesn't always please
people, even if the change is for the better.
Signed-off-by: Joern Engel <joern@wohnheim.fh-wedel.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>

drivers/mtd/devices/block2mtd.c

@@ -4,7 +4,7 @@
  * block2mtd.c - create an mtd from a block device
  *
  * Copyright (C) 2001,2002	Simon Evans <spse@secret.org.uk>
- * Copyright (C) 2004,2005	Jrn Engel <joern@wh.fh-wedel.de>
+ * Copyright (C) 2004-2006	Jrn Engel <joern@wh.fh-wedel.de>
  *
  * Licence: GPL
  */
@@ -351,6 +351,12 @@ static struct block2mtd_dev *add_device(char *devname, int erase_size)
 }
 
 
+/* This function works similar to reguler strtoul.  In addition, it
+ * allows some suffixes for a more human-readable number format:
+ * ki, Ki, kiB, KiB	- multiply result with 1024
+ * Mi, MiB		- multiply result with 1024^2
+ * Gi, GiB		- multiply result with 1024^3
+ */
 static int ustrtoul(const char *cp, char **endp, unsigned int base)
 {
 	unsigned long result = simple_strtoul(cp, endp, base);
@@ -359,12 +365,17 @@ static int ustrtoul(const char *cp, char **endp, unsigned int base)
 		result *= 1024;
 	case 'M':
 		result *= 1024;
+	case 'K':
 	case 'k':
 		result *= 1024;
 	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
-		if ((*endp)[1] == 'i')
+		if ((*endp)[1] == 'i') {
+			if ((*endp)[2] == 'B')
+				(*endp) += 3;
+			else
 				(*endp) += 2;
 		}
+	}
 	return result;
 }