pread.h

   1 /*
   2  *      The PCI Library -- Portable interface to pread() and pwrite()
   3  *
   4  *      Copyright (c) 1997--2003 Martin Mares <mj@ucw.cz>
   5  *
   6  *      Can be freely distributed and used under the terms of the GNU GPL v2+
   7  *
   8  *      SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 /*
  12  *  We'd like to use pread/pwrite for configuration space accesses, but
  13  *  unfortunately it isn't simple at all since all libc's until glibc 2.1
  14  *  don't define it.
  15  */
  16
  17 #if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ > 0
  18 /* glibc 2.1 or newer -> pread/pwrite supported automatically */
  19
  20 #elif defined(i386) && defined(__GLIBC__)
  21 /* glibc 2.0 on i386 -> call syscalls directly */
  22 #include <asm/unistd.h>
  23 #include <syscall-list.h>
  24 #ifndef SYS_pread
  25 #define SYS_pread 180
  26 #endif
  27 static int pread(unsigned int fd, void *buf, size_t size, loff_t where)
  28 { return syscall(SYS_pread, fd, buf, size, where); }
  29 #ifndef SYS_pwrite
  30 #define SYS_pwrite 181
  31 #endif
  32 static int pwrite(unsigned int fd, void *buf, size_t size, loff_t where)
  33 { return syscall(SYS_pwrite, fd, buf, size, where); }
  34
  35 #else
  36 /* In all other cases we use lseek/read/write instead to be safe */
  37 #define make_rw_glue(op) \
  38         static int do_##op(struct pci_dev *d, int fd, void *buf, size_t size, int where)        \
  39         {                                                                                       \
  40           struct pci_access *a = d->access;                                                     \
  41           int r;                                                                                \
  42           if (a->fd_pos != where && lseek(fd, where, SEEK_SET) < 0)                             \
  43             return -1;                                                                          \
  44           r = op(fd, buf, size);                                                                \
  45           if (r < 0)                                                                            \
  46             a->fd_pos = -1;                                                                     \
  47           else                                                                                  \
  48             a->fd_pos = where + r;                                                              \
  49           return r;                                                                             \
  50         }
  51 make_rw_glue(read)
  52 make_rw_glue(write)
  53 #define PCI_HAVE_DO_READ
  54 #endif
  55
  56 #ifndef PCI_HAVE_DO_READ
  57 #define do_read(d,f,b,l,p) pread(f,b,l,p)
  58 #define do_write(d,f,b,l,p) pwrite(f,b,l,p)
  59 #endif