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