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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Filesystem parameter description and parser
* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (
#include <linux/fs_context.h>
struct path;
struct constant_table {
const char *name;
int value;
* The type of parameter expected.
enum fs_parameter_type {
* Specification of the type of value a parameter wants.
* Note that the fsparam_flag(), fsparam_string(), fsparam_u32(), ... macros
* should be used to generate elements of this type.
struct fs_parameter_spec {
const char *name;
u8 opt; /* Option number (returned by fs_parse()) */
enum fs_parameter_type type:8; /* The desired parameter type */
unsigned short flags;
#define fs_param_v_optional 0x0001 /* The value is optional */
#define fs_param_neg_with_no 0x0002 /* "noxxx" is negative param */
#define fs_param_neg_with_empty 0x0004 /* "xxx=" is negative param */
#define fs_param_deprecated 0x0008 /* The param is deprecated */
struct fs_parameter_enum {
u8 opt; /* Option number (as fs_parameter_spec::opt) */
char name[14];
u8 value;
struct fs_parameter_description {
const char name[16]; /* Name for logging purposes */
const struct fs_parameter_spec *specs; /* List of param specifications */
const struct fs_parameter_enum *enums; /* Enum values */
* Result of parse.
struct fs_parse_result {
bool negated; /* T if param was "noxxx" */
bool has_value; /* T if value supplied to param */
union {
bool boolean; /* For spec_bool */
int int_32; /* For spec_s32/spec_enum */
unsigned int uint_32; /* For spec_u32{,_octal,_hex}/spec_enum */
u64 uint_64; /* For spec_u64 */
extern int fs_parse(struct fs_context *fc,
const struct fs_parameter_description *desc,
struct fs_parameter *value,
struct fs_parse_result *result);
extern int fs_lookup_param(struct fs_context *fc,
struct fs_parameter *param,
bool want_bdev,
struct path *_path);
extern int __lookup_constant(const struct constant_table tbl[], size_t tbl_size,
const char *name, int not_found);
#define lookup_constant(t, n, nf) __lookup_constant(t, ARRAY_SIZE(t), (n), (nf))
extern bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
int low, int high, int special);
extern bool fs_validate_description(const struct fs_parameter_description *desc);
static inline bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
int low, int high, int special)
{ return true; }
static inline bool fs_validate_description(const struct fs_parameter_description *desc)
{ return true; }
* Parameter type, name, index and flags element constructors. Use as:
* fsparam_xxxx("foo", Opt_foo)
* If existing helpers are not enough, direct use of __fsparam() would
* work, but any such case is probably a sign that new helper is needed.
* Helpers will remain stable; low-level implementation may change.
#define __fsparam(TYPE, NAME, OPT, FLAGS) \
{ \
.name = NAME, \
.opt = OPT, \
.type = TYPE, \
.flags = FLAGS \
#define fsparam_flag(NAME, OPT) __fsparam(fs_param_is_flag, NAME, OPT, 0)
#define fsparam_flag_no(NAME, OPT) \
__fsparam(fs_param_is_flag, NAME, OPT, \
#define fsparam_bool(NAME, OPT) __fsparam(fs_param_is_bool, NAME, OPT, 0)
#define fsparam_u32(NAME, OPT) __fsparam(fs_param_is_u32, NAME, OPT, 0)
#define fsparam_u32oct(NAME, OPT) \
__fsparam(fs_param_is_u32_octal, NAME, OPT, 0)
#define fsparam_u32hex(NAME, OPT) \
__fsparam(fs_param_is_u32_hex, NAME, OPT, 0)
#define fsparam_s32(NAME, OPT) __fsparam(fs_param_is_s32, NAME, OPT, 0)
#define fsparam_u64(NAME, OPT) __fsparam(fs_param_is_u64, NAME, OPT, 0)
#define fsparam_enum(NAME, OPT) __fsparam(fs_param_is_enum, NAME, OPT, 0)
#define fsparam_string(NAME, OPT) \
__fsparam(fs_param_is_string, NAME, OPT, 0)
#define fsparam_blob(NAME, OPT) __fsparam(fs_param_is_blob, NAME, OPT, 0)
#define fsparam_bdev(NAME, OPT) __fsparam(fs_param_is_blockdev, NAME, OPT, 0)
#define fsparam_path(NAME, OPT) __fsparam(fs_param_is_path, NAME, OPT, 0)
#define fsparam_fd(NAME, OPT) __fsparam(fs_param_is_fd, NAME, OPT, 0)
#endif /* _LINUX_FS_PARSER_H */