[PATCH v2 1/3] fs_parser: add helper to define parameters with string and flag types

[Luis Henriques <lhenriques@suse.de>]

Add a new helper macro that defines two new parameters, both with the same
name, but one of type 'string' and another of type 'flag'.  The 'string'
parameter may also be empty (i.e. without value).  In practice this helper
allows a filesystem to easily define a parameter that can be empty (flag)
or have a value (string).

Suggested-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Luis Henriques <lhenriques@suse.de>
---
 include/linux/fs_parser.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/fs_parser.h b/include/linux/fs_parser.h
index 01542c4b87a2..f582fb7bdc22 100644
--- a/include/linux/fs_parser.h
+++ b/include/linux/fs_parser.h
@@ -131,5 +131,13 @@ static inline bool fs_validate_description(const char *name,
 #define fsparam_bdev(NAME, OPT)	__fsparam(fs_param_is_blockdev, NAME, OPT, 0, NULL)
 #define fsparam_path(NAME, OPT)	__fsparam(fs_param_is_path, NAME, OPT, 0, NULL)
 #define fsparam_fd(NAME, OPT)	__fsparam(fs_param_is_fd, NAME, OPT, 0, NULL)
+/*
+ * Define two parameters with the same name, with types string and flag.  The
+ * string parameter can be empty, and thus it effectively allows the parameter
+ * to have a value or to be empty.
+ */
+#define fsparam_string_or_flag(NAME, OPT)				\
+	__fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL), \
+	fsparam_flag(NAME, OPT)
 
 #endif /* _LINUX_FS_PARSER_H */