include/linux/uio.h

   1 #ifndef __LINUX_UIO_H
   2 #define __LINUX_UIO_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/types.h>
   6
   7 /*
   8  *      Berkeley style UIO structures   -       Alan Cox 1994.
   9  *
  10  *              This program is free software; you can redistribute it and/or
  11  *              modify it under the terms of the GNU General Public License
  12  *              as published by the Free Software Foundation; either version
  13  *              2 of the License, or (at your option) any later version.
  14  */
  15
  16
  17 /* A word of warning: Our uio structure will clash with the C library one (which is now obsolete). Remove the C
  18    library one from sys/uio.h if you have a very old library set */
  19
  20 struct iovec
  21 {
  22         void __user *iov_base;  /* BSD uses caddr_t (1003.1g requires void *) */
  23         __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
  24 };
  25
  26 /*
  27  *      UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
  28  */
  29
  30 #define UIO_FASTIOV     8
  31 #define UIO_MAXIOV      1024
  32 #if 0
  33 #define UIO_MAXIOV      16      /* Maximum iovec's in one operation
  34                                    16 matches BSD */
  35                                 /* Beg pardon: BSD has 1024 --ANK */
  36 #endif
  37
  38 /*
  39  * Total number of bytes covered by an iovec.
  40  *
  41  * NOTE that it is not safe to use this function until all the iovec's
  42  * segment lengths have been validated.  Because the individual lengths can
  43  * overflow a size_t when added together.
  44  */
  45 static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  46 {
  47         unsigned long seg;
  48         size_t ret = 0;
  49
  50         for (seg = 0; seg < nr_segs; seg++)
  51                 ret += iov[seg].iov_len;
  52         return ret;
  53 }
  54
  55 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  56
  57 #endif