fs/fat: Clean up open-coded sector <-> cluster conversions

Use the clust_to_sect() helper that was introduced earlier, and add an
inverse sect_to_clust(), plus update the various spots that open-coded
this conversion previously.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

fs/fat/fat.c

@@ -257,8 +257,7 @@ get_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer, unsigned long size)
 	int ret;
 
 	if (clustnum > 0) {
-		startsect = mydata->data_begin +
-				clustnum * mydata->clust_size;
+		startsect = clust_to_sect(mydata, clustnum);
 	} else {
 		startsect = mydata->rootdir_sect;
 	}
@@ -594,9 +593,8 @@ static int get_fs_info(fsdata *mydata)
 		mydata->data_begin = mydata->rootdir_sect +
 					mydata->rootdir_size -
 					(mydata->clust_size * 2);
-		mydata->root_cluster = (mydata->rootdir_sect -
-					mydata->data_begin) /
-					mydata->clust_size;
+		mydata->root_cluster =
+			sect_to_clust(mydata, mydata->rootdir_sect);
 	}
 
 	mydata->fatbufnum = -1;

fs/fat/fat_write.c

@@ -502,8 +502,7 @@ set_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer,
 	int ret;
 
 	if (clustnum > 0)
-		startsect = mydata->data_begin +
-				clustnum * mydata->clust_size;
+		startsect = clust_to_sect(mydata, clustnum);
 	else
 		startsect = mydata->rootdir_sect;
 
@@ -751,8 +750,7 @@ static int check_overflow(fsdata *mydata, __u32 clustnum, loff_t size)
 	__u32 startsect, sect_num, offset;
 
 	if (clustnum > 0) {
-		startsect = mydata->data_begin +
-				clustnum * mydata->clust_size;
+		startsect = clust_to_sect(mydata, clustnum);
 	} else {
 		startsect = mydata->rootdir_sect;
 	}
@@ -791,7 +789,7 @@ static dir_entry *empty_dentptr;
 static dir_entry *find_directory_entry(fsdata *mydata, int startsect,
 	char *filename, dir_entry *retdent, __u32 start)
 {
-	__u32 curclust = (startsect - mydata->data_begin) / mydata->clust_size;
+	__u32 curclust = sect_to_clust(mydata, startsect);
 
 	debug("get_dentfromdir: %s\n", filename);
 

include/fat.h

@@ -177,12 +177,16 @@ typedef struct {
 	__u32	root_cluster;	/* First cluster of root dir for FAT32 */
 } fsdata;
 
-/* TODO clean up places that are open-coding this: */
 static inline u32 clust_to_sect(fsdata *fsdata, u32 clust)
 {
 	return fsdata->data_begin + clust * fsdata->clust_size;
 }
 
+static inline u32 sect_to_clust(fsdata *fsdata, u32 sect)
+{
+	return (sect - fsdata->data_begin) / fsdata->clust_size;
+}
+
 int file_fat_detectfs(void);
 int fat_exists(const char *filename);
 int fat_size(const char *filename, loff_t *size);