fs: fat: Fix mkcksum() function parameters

The mkcksum() function now takes one parameter, the pointer to
11-byte wide character array, which it then operates on.

Currently, the function is wrongly passed (dir_entry)->name, which
is only 8-byte wide character array. Though by further inspecting
the dir_entry structure, it can be noticed that the name[8] entry
is immediatelly followed by ext[3] entry. Thus, name[8] and ext[3]
in the dir_entry structure actually work as this 11-byte wide array
since they're placed right next to each other by current compiler
behavior.

Depending on this is obviously wrong, thus fix this by correctly
passing both (dir_entry)->name and (dir_entry)->ext to the mkcksum()
function and adjust the function appropriately.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@ti.com>

fs/fat/fat.c

@@ -567,15 +567,16 @@ get_vfatname(fsdata *mydata, int curclust, __u8 *cluster,
 }
 
 /* Calculate short name checksum */
-static __u8 mkcksum(const char *str)
+static __u8 mkcksum(const char name[8], const char ext[3])
 {
 	int i;
 
 	__u8 ret = 0;
 
-	for (i = 0; i < 11; i++) {
-		ret = (((ret & 1) << 7) | ((ret & 0xfe) >> 1)) + str[i];
-	}
+	for (i = 0; i < sizeof(name); i++)
+		ret = (((ret & 1) << 7) | ((ret & 0xfe) >> 1)) + name[i];
+	for (i = 0; i < sizeof(ext); i++)
+		ret = (((ret & 1) << 7) | ((ret & 0xfe) >> 1)) + ext[i];
 
 	return ret;
 }
@@ -678,7 +679,8 @@ static dir_entry *get_dentfromdir(fsdata *mydata, int startsect,
 				return NULL;
 			}
 #ifdef CONFIG_SUPPORT_VFAT
-			if (dols && mkcksum(dentptr->name) == prevcksum) {
+			__u8 csum = mkcksum(dentptr->name, dentptr->ext);
+			if (dols && csum == prevcksum) {
 				prevcksum = 0xffff;
 				dentptr++;
 				continue;
@@ -946,13 +948,16 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 
 		for (i = 0; i < DIRENTSPERBLOCK; i++) {
 			char s_name[14], l_name[VFAT_MAXLEN_BYTES];
+			__u8 csum;
 
 			l_name[0] = '\0';
 			if (dentptr->name[0] == DELETED_FLAG) {
 				dentptr++;
 				continue;
 			}
-			if ((dentptr->attr & ATTR_VOLUME)) {
+
+			csum = mkcksum(dentptr->name, dentptr->ext);
+			if (dentptr->attr & ATTR_VOLUME) {
 #ifdef CONFIG_SUPPORT_VFAT
 				if ((dentptr->attr & ATTR_VFAT) == ATTR_VFAT &&
 				    (dentptr->name[0] & LAST_LONG_ENTRY_MASK)) {
@@ -1015,8 +1020,7 @@ do_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 				goto exit;
 			}
 #ifdef CONFIG_SUPPORT_VFAT
-			else if (dols == LS_ROOT &&
-				 mkcksum(dentptr->name) == prevcksum) {
+			else if (dols == LS_ROOT && csum == prevcksum) {
 				prevcksum = 0xffff;
 				dentptr++;
 				continue;

fs/fat/fat_write.c

@@ -335,7 +335,7 @@ fill_dir_slot(fsdata *mydata, dir_entry **dentptr, const char *l_name)
 
 	/* Get short file name and checksum value */
 	strncpy(s_name, (*dentptr)->name, 16);
-	checksum = mkcksum(s_name);
+	checksum = mkcksum((*dentptr)->name, (*dentptr)->ext);
 
 	do {
 		memset(slotptr, 0x00, sizeof(dir_slot));