fat: implement exists() for FAT fs

This hooks into the generic "file exists" support added in an earlier
patch, and provides an implementation for the FAT filesystem.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

fs/fat/fat.c

@@ -808,7 +808,7 @@ __u8 do_fat_read_at_block[MAX_CLUSTSIZE]
 
 long
 do_fat_read_at(const char *filename, unsigned long pos, void *buffer,
-	       unsigned long maxsize, int dols)
+	       unsigned long maxsize, int dols, int dogetsize)
 {
 	char fnamecopy[2048];
 	boot_sector bs;
@@ -1152,7 +1152,10 @@ rootdir_done:
 			subname = nextname;
 	}
 
-	ret = get_contents(mydata, dentptr, pos, buffer, maxsize);
+	if (dogetsize)
+		ret = FAT2CPU32(dentptr->size);
+	else
+		ret = get_contents(mydata, dentptr, pos, buffer, maxsize);
 	debug("Size: %d, got: %ld\n", FAT2CPU32(dentptr->size), ret);
 
 exit:
@@ -1163,7 +1166,7 @@ exit:
 long
 do_fat_read(const char *filename, void *buffer, unsigned long maxsize, int dols)
 {
-	return do_fat_read_at(filename, 0, buffer, maxsize, dols);
+	return do_fat_read_at(filename, 0, buffer, maxsize, dols, 0);
 }
 
 int file_fat_detectfs(void)
@@ -1233,11 +1236,18 @@ int file_fat_ls(const char *dir)
 	return do_fat_read(dir, NULL, 0, LS_YES);
 }
 
+int fat_exists(const char *filename)
+{
+	int sz;
+	sz = do_fat_read_at(filename, 0, NULL, 0, LS_NO, 1);
+	return sz >= 0;
+}
+
 long file_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 		      unsigned long maxsize)
 {
 	printf("reading %s\n", filename);
-	return do_fat_read_at(filename, pos, buffer, maxsize, LS_NO);
+	return do_fat_read_at(filename, pos, buffer, maxsize, LS_NO, 0);
 }
 
 long file_fat_read(const char *filename, void *buffer, unsigned long maxsize)

fs/fs.c

@@ -90,7 +90,7 @@ static struct fstype_info fstypes[] = {
 		.probe = fat_set_blk_dev,
 		.close = fat_close,
 		.ls = file_fat_ls,
-		.exists = fs_exists_unsupported,
+		.exists = fat_exists,
 		.read = fat_read_file,
 		.write = fs_write_unsupported,
 	},

include/fat.h

@@ -188,6 +188,7 @@ file_read_func		file_fat_read;
 int file_cd(const char *path);
 int file_fat_detectfs(void);
 int file_fat_ls(const char *dir);
+int fat_exists(const char *filename);
 long file_fat_read_at(const char *filename, unsigned long pos, void *buffer,
 		      unsigned long maxsize);
 long file_fat_read(const char *filename, void *buffer, unsigned long maxsize);