fs: sdfat: add config option to register sdFAT for exFAT

Signed-off-by: Jesse Chan <jc@linux.com>

fs/sdfat/Kconfig

@@ -15,6 +15,13 @@ config SDFAT_FS
 	  To compile this as a module, choose M here: the module will be called
 	  sdfat_core and sdfat_fs.
 
+config SDFAT_USE_FOR_EXFAT
+	bool "Register sdFAT as exFAT"
+	default y
+	depends on SDFAT_FS && !EXFAT_FS
+	help
+	  If you want to register sdFAT as available for exFAT, say Y.
+
 config SDFAT_DELAYED_META_DIRTY
 	bool "Enable delayed metadata dirty"
 	default y

fs/sdfat/sdfat.c

@@ -5087,6 +5087,20 @@ static struct file_system_type sdfat_fs_type = {
 	.fs_flags    = FS_REQUIRES_DEV,
 };
 
+#ifdef CONFIG_SDFAT_USE_FOR_EXFAT
+static struct file_system_type exfat_fs_type = {
+	.owner       = THIS_MODULE,
+	.name        = "exfat",
+	.mount       = sdfat_fs_mount,
+#ifdef CONFIG_SDFAT_DBG_IOCTL
+	.kill_sb    = sdfat_debug_kill_sb,
+#else
+	.kill_sb    = kill_block_super,
+#endif /* CONFIG_SDFAT_DBG_IOCTL */
+	.fs_flags    = FS_REQUIRES_DEV,
+};
+#endif /* CONFIG_SDFAT_USE_FOR_EXFAT */
+
 static int __init init_sdfat_fs(void)
 {
 	int err;
@@ -5129,6 +5143,14 @@ static int __init init_sdfat_fs(void)
 		goto error;
 	}
 
+#ifdef CONFIG_SDFAT_USE_FOR_EXFAT
+	err = register_filesystem(&exfat_fs_type);
+	if (err) {
+		pr_err("[SDFAT] failed to register for exfat filesystem\n");
+		goto error;
+	}
+#endif /* CONFIG_SDFAT_USE_FOR_EXFAT */
+
 	return 0;
 error:
 	sdfat_uevent_uninit();
@@ -5160,7 +5182,9 @@ static void __exit exit_sdfat_fs(void)
 
 	sdfat_destroy_inodecache();
 	unregister_filesystem(&sdfat_fs_type);
-
+#ifdef CONFIG_SDFAT_USE_FOR_EXFAT
+	unregister_filesystem(&exfat_fs_type);
+#endif /* CONFIG_SDFAT_USE_FOR_EXFAT */
 	fsapi_shutdown();
 }