bits/sysmacros.h

   1 /* Definitions of macros to access `dev_t' values.
   2    Copyright (C) 1996-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _BITS_SYSMACROS_H
  20 #define _BITS_SYSMACROS_H 1
  21
  22 #ifndef _SYS_SYSMACROS_H
  23 # error "Never include <bits/sysmacros.h> directly; use <sys/sysmacros.h> instead."
  24 #endif
  25
  26 /* dev_t in glibc is a 64-bit quantity, with 32-bit major and minor numbers.
  27    Our default encoding is MMMM Mmmm mmmM MMmm, where M is a hex digit of
  28    the major number and m is a hex digit of the minor number.  This is
  29    downward compatible with legacy systems where dev_t is 16 bits wide,
  30    encoded as MMmm.  It is also downward compatible with the Linux kernel,
  31    which (as of 2016) uses 32-bit dev_t, encoded as mmmM MMmm.
  32
  33    Systems that use an incompatible encoding for dev_t should override this
  34    file in the appropriate sysdeps subdirectory.  */
  35
  36 #define __SYSMACROS_DECLARE_MAJOR(DECL_TEMPL)                   \
  37   DECL_TEMPL(unsigned int, major, (__dev_t __dev))
  38
  39 #define __SYSMACROS_DEFINE_MAJOR(DECL_TEMPL)                    \
  40   __SYSMACROS_DECLARE_MAJOR (DECL_TEMPL)                        \
  41   {                                                             \
  42     unsigned int __major;                                       \
  43     __major  = ((__dev & (__dev_t) 0x00000000000fff00u) >>  8); \
  44     __major |= ((__dev & (__dev_t) 0xfffff00000000000u) >> 32); \
  45     return __major;                                             \
  46   }
  47
  48 #define __SYSMACROS_DECLARE_MINOR(DECL_TEMPL)                   \
  49   DECL_TEMPL(unsigned int, minor, (__dev_t __dev))
  50
  51 #define __SYSMACROS_DEFINE_MINOR(DECL_TEMPL)                    \
  52   __SYSMACROS_DECLARE_MINOR (DECL_TEMPL)                        \
  53   {                                                             \
  54     unsigned int __minor;                                       \
  55     __minor  = ((__dev & (__dev_t) 0x00000000000000ffu) >>  0); \
  56     __minor |= ((__dev & (__dev_t) 0x00000ffffff00000u) >> 12); \
  57     return __minor;                                             \
  58   }
  59
  60 #define __SYSMACROS_DECLARE_MAKEDEV(DECL_TEMPL)                 \
  61   DECL_TEMPL(__dev_t, makedev, (unsigned int __major, unsigned int __minor))
  62
  63 #define __SYSMACROS_DEFINE_MAKEDEV(DECL_TEMPL)                  \
  64   __SYSMACROS_DECLARE_MAKEDEV (DECL_TEMPL)                      \
  65   {                                                             \
  66     __dev_t __dev;                                              \
  67     __dev  = (((__dev_t) (__major & 0x00000fffu)) <<  8);       \
  68     __dev |= (((__dev_t) (__major & 0xfffff000u)) << 32);       \
  69     __dev |= (((__dev_t) (__minor & 0x000000ffu)) <<  0);       \
  70     __dev |= (((__dev_t) (__minor & 0xffffff00u)) << 12);       \
  71     return __dev;                                               \
  72   }
  73
  74 #endif /* bits/sysmacros.h */