fat: Define MAX_CLUSTSIZE using CONFIG_FS_FAT_MAX_CLUSTSIZE

Define the MAX_CLUSTSIZE to default of 65536 only if
CONFIG_FS_FAT_MAX_CLUSTSIZE is not defined.
This option has been provided to save memory in some
memory constrained cases.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Acked-by: Michal Simek <monstr@monstr.eu>

README

@@ -1637,6 +1637,12 @@ CBFS (Coreboot Filesystem) support
 		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
 		and cbfsload.
 
+- FAT(File Allocation Table) filesystem cluster size:
+		CONFIG_FS_FAT_MAX_CLUSTSIZE
+
+		Define the max cluster size for fat operations else
+		a default value of 65536 will be defined.
+
 - Keyboard Support:
 		CONFIG_ISA_KEYBOARD
 

include/fat.h

@@ -18,7 +18,11 @@
 #define VFAT_MAXSEQ		9   /* Up to 9 of 13 2-byte UTF-16 entries */
 #define PREFETCH_BLOCKS		2
 
-#define MAX_CLUSTSIZE	65536
+#ifndef CONFIG_FS_FAT_MAX_CLUSTSIZE
+#define CONFIG_FS_FAT_MAX_CLUSTSIZE 65536
+#endif
+#define MAX_CLUSTSIZE	CONFIG_FS_FAT_MAX_CLUSTSIZE
+
 #define DIRENTSPERBLOCK	(mydata->sect_size / sizeof(dir_entry))
 #define DIRENTSPERCLUST	((mydata->clust_size * mydata->sect_size) / \
 			 sizeof(dir_entry))