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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 0.19
       Copyright (C) 2008 Peter Miller

                                                              explain_ioctl(3)