src/basic/devnum-util.h

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 #pragma once
   3
   4 #include <inttypes.h>
   5 #include <stdbool.h>
   6 #include <sys/types.h>
   7
   8 #include "stdio-util.h"
   9
  10 int parse_devnum(const char *s, dev_t *ret);
  11
  12 /* glibc and the Linux kernel have different ideas about the major/minor size. These calls will check whether the
  13  * specified major is valid by the Linux kernel's standards, not by glibc's. Linux has 20bits of minor, and 12 bits of
  14  * major space. See MINORBITS in linux/kdev_t.h in the kernel sources. (If you wonder why we define _y here, instead of
  15  * comparing directly >= 0: it's to trick out -Wtype-limits, which would otherwise complain if the type is unsigned, as
  16  * such a test would be pointless in such a case.) */
  17
  18 #define DEVICE_MAJOR_VALID(x)                                           \
  19         ({                                                              \
  20                 typeof(x) _x = (x), _y = 0;                             \
  21                 _x >= _y && _x < (UINT32_C(1) << 12);                   \
  22                                                                         \
  23         })
  24
  25 #define DEVICE_MINOR_VALID(x)                                           \
  26         ({                                                              \
  27                 typeof(x) _x = (x), _y = 0;                             \
  28                 _x >= _y && _x < (UINT32_C(1) << 20);                   \
  29         })
  30
  31 int device_path_make_major_minor(mode_t mode, dev_t devnum, char **ret);
  32 int device_path_make_inaccessible(mode_t mode, char **ret);
  33 int device_path_make_canonical(mode_t mode, dev_t devnum, char **ret);
  34 int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret_devnum);
  35
  36 static inline bool devnum_set_and_equal(dev_t a, dev_t b) {
  37         /* Returns true if a and b definitely refer to the same device. If either is zero, this means "don't
  38          * know" and we'll return false */
  39         return a == b && a != 0;
  40 }
  41
  42 /* Maximum string length for a major:minor string. (Note that DECIMAL_STR_MAX includes space for a trailing NUL) */
  43 #define DEVNUM_STR_MAX (DECIMAL_STR_MAX(dev_t)-1+1+DECIMAL_STR_MAX(dev_t))
  44
  45 #define DEVNUM_FORMAT_STR "%u:%u"
  46 #define DEVNUM_FORMAT_VAL(d) major(d), minor(d)
  47
  48 static inline char *format_devnum(dev_t d, char buf[static DEVNUM_STR_MAX]) {
  49         return ASSERT_PTR(snprintf_ok(buf, DEVNUM_STR_MAX, DEVNUM_FORMAT_STR, DEVNUM_FORMAT_VAL(d)));
  50 }
  51
  52 #define FORMAT_DEVNUM(d) format_devnum((d), (char[DEVNUM_STR_MAX]) {})
  53
  54 static inline bool devnum_is_zero(dev_t d) {
  55         return major(d) == 0 && minor(d) == 0;
  56 }