linux/include/linux/err.h
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   1#ifndef _LINUX_ERR_H
   2#define _LINUX_ERR_H
   3
   4#include <linux/compiler.h>
   5
   6#include <asm/errno.h>
   7
   8/*
   9 * Kernel pointers have redundant information, so we can use a
  10 * scheme where we can return either an error code or a dentry
  11 * pointer with the same return value.
  12 *
  13 * This should be a per-architecture thing, to allow different
  14 * error and pointer decisions.
  15 */
  16#define MAX_ERRNO       4095
  17
  18#ifndef __ASSEMBLY__
  19
  20#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
  21
  22static inline void *ERR_PTR(long error)
  23{
  24        return (void *) error;
  25}
  26
  27static inline long PTR_ERR(const void *ptr)
  28{
  29        return (long) ptr;
  30}
  31
  32static inline long IS_ERR(const void *ptr)
  33{
  34        return IS_ERR_VALUE((unsigned long)ptr);
  35}
  36
  37/**
  38 * ERR_CAST - Explicitly cast an error-valued pointer to another pointer type
  39 * @ptr: The pointer to cast.
  40 *
  41 * Explicitly cast an error-valued pointer to another pointer type in such a
  42 * way as to make it clear that's what's going on.
  43 */
  44static inline void *ERR_CAST(const void *ptr)
  45{
  46        /* cast away the const */
  47        return (void *) ptr;
  48}
  49
  50#endif
  51
  52#endif /* _LINUX_ERR_H */
  53
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