NAME

       explain_ioctl - explain ioctl(2) errors

SYNOPSIS

       #include <libexplain/ioctl.h>
       const char *explain_ioctl(int fildes, int request, void *data);
       const char *explain_errno_ioctl(int errnum, int fildes, int request, void *data);
       void  explain_message_ioctl(char *message, int message_size, int fildes, int request, void
       *data);
       void explain_message_errno_ioctl(char *message, int message_size, int errnum, int  fildes,
       int request, void *data);

DESCRIPTION

       These  functions  may  be  used to obtain explanations for errors returned by the ioctl(2)
       system call.

   explain_ioctl
       const char *explain_ioctl(int fildes, int request, void *data);

       The explain_ioctl function is used to obtain an explanation of an error  returned  by  the
       ioctl(2) system call.  The least the message will contain is the value of strerror(errno),
       but usually it will do much better, and indicate the underlying cause in more detail.

       The errno global variable will be used to obtain the error value to be decoded.

       This function is intended to be used in a fashion similar to the following example:
              int result = ioctl(fildes, request, data);
              if (result < 0)
              {
                  fprintf(stderr, "%s\n", explain_ioctl(fildes, request, data));
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ioctl_or_die(3) function.

       fildes  The original fildes, exactly as passed to the ioctl(2) system call.

       request The original request, exactly as passed to the ioctl(2) system call.

       data    The original data, exactly as passed to the ioctl(2) system call.

       Returns:
               The message explaining the error.  This message buffer is shared by all libexplain
               functions  which  do  not  supply  a  buffer in their argument list.  This will be
               overwritten by the next call to any libexplain function which shares this  buffer,
               including other threads.

       Note:  This  function  is  not  thread  safe, because it shares a return buffer across all
       threads, and many other functions in this library.

   explain_errno_ioctl
       const char *explain_errno_ioctl(int errnum, int fildes, int request, void *data);

       The explain_errno_ioctl function is used to obtain an explanation of an error returned  by
       the  ioctl(2)  system  call.   The  least  the  message  will  contain  is  the  value  of
       strerror(errnum), but usually it will do much better, and indicate the underlying cause in
       more detail.

       This function is intended to be used in a fashion similar to the following example:
              if (ioctl(fildes, request, data) < 0)
              {
                  int err = errno;
                  fprintf(stderr, "%s\n",
                      explain_errno_ioctl(err, fildes, request, data));
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ioctl_or_die(3) function.

       errnum  The  error  value  to  be decoded, usually obtained from the errno global variable
               just before this function is called.  This is necessary if you need  to  call  any
               code  between the system call to be explained and this function, because many libc
               functions will alter the value of errno.

       fildes  The original fildes, exactly as passed to the ioctl(2) system call.

       request The original request, exactly as passed to the ioctl(2) system call.

       data    The original data, exactly as passed to the ioctl(2) system call.

       Returns:
               The message explaining the error.  This message buffer is shared by all libexplain
               functions  which  do  not  supply  a  buffer in their argument list.  This will be
               overwritten by the next call to any libexplain function which shares this  buffer,
               including other threads.

       Note:  This  function  is  not  thread  safe, because it shares a return buffer across all
       threads, and many other functions in this library.

   explain_message_ioctl
       void explain_message_ioctl(char *message, int message_size, int fildes, int request,  void
       *data);

       The  explain_message_ioctl  function  may  be  used  to  obtain an explanation of an error
       returned by the ioctl(2) system call.  The least the message will contain is the value  of
       strerror(errno),  but usually it will do much better, and indicate the underlying cause in
       more detail.

       The errno global variable will be used to obtain the error value to be decoded.

       This function is intended to be used in a fashion similar to the following example:
              if (ioctl(fildes, request, data) < 0)
              {
                  char message[3000];
                  explain_message_ioctl(message, sizeof(message), fildes, request, data);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ioctl_or_die(3) function.

       message The location in which to store the returned message.  If a suitable message return
               buffer is supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned message.

       fildes  The original fildes, exactly as passed to the ioctl(2) system call.

       request The original request, exactly as passed to the ioctl(2) system call.

       data    The original data, exactly as passed to the ioctl(2) system call.

   explain_message_errno_ioctl
       void  explain_message_errno_ioctl(char *message, int message_size, int errnum, int fildes,
       int request, void *data);

       The explain_message_errno_ioctl function may be used to obtain an explanation of an  error
       returned  by the ioctl(2) system call.  The least the message will contain is the value of
       strerror(errnum), but usually it will do much better, and indicate the underlying cause in
       more detail.

       This function is intended to be used in a fashion similar to the following example:
              if (ioctl(fildes, request, data) < 0)
              {
                  int err = errno;
                  char message[3000];
                  explain_message_errno_ioctl(message, sizeof(message), err,
                      fildes, request, data);
                  fprintf(stderr, "%s\n", message);
                  exit(EXIT_FAILURE);
              }

       The above code example is available pre‐packaged as the explain_ioctl_or_die(3) function.

       message The location in which to store the returned message.  If a suitable message return
               buffer is supplied, this function is thread safe.

       message_size
               The size in bytes of the location in which to store the returned message.

       errnum  The error value to be decoded, usually obtained from  the  errno  global  variable
               just  before  this  function is called.  This is necessary if you need to call any
               code between the system call to be explained and this function, because many  libc
               functions will alter the value of errno.

       fildes  The original fildes, exactly as passed to the ioctl(2) system call.

       request The original request, exactly as passed to the ioctl(2) system call.

       data    The original data, exactly as passed to the ioctl(2) system call.

SEE ALSO

       ioctl(2)
               control device

       explain_ioctl_or_die(3)
               control device and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2008 Peter Miller

                                                                                 explain_ioctl(3)