_register_ioctl_handler()

Updated: May 06, 2022

Register an I/O control handler

Synopsis:

#include <ioctl.h>

int _register_ioctl_handler( _ioctl_handler_fct *function,
                             int command_min,
                             int command_max );

Arguments:

function
An I/O control handler function of type _ioctl_handler_fct. Its prototype is described below.
command_min
Specifies the first command in a range of commands that the function handles. The specified range must be continuous. For commands that fall outside the range, register additional ranges as required.
command_max
Specifies the last command in a range of commands that the function handles.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The _register_ioctl_handler() function registers an I/O control command handler.

The handler function prototype is:

typedef int (*_ioctl_handler_fct)( int fd,
                                   int request,
                                   va_list arg );

The arguments are:

fd
An open file descriptor for the file or device that you want to manipulate.
request
The I/O control command. For a list of commands, see ioctl(), vioctl().
arg
A variable-argument list of the additional arguments, which you must have initialized with the va_start() macro.

Like ioctl(), this handler function returns a value based on the request, or -1 if an error occurs (errno is set).

Returns:

EOK
Success.
ENOMEM
Insufficient memory to allocate internal data structures.

Examples:

static int my_ioctl_handler(const int fd, const int cmd, va_list vl)
{
    /* fill in details */
    errno = ENOTSUP;
    return -1;
}

/* Automatic registration of the ioctl handler with libc */
static void __attribute__ ((constructor)) my_ioctl_handler_init()
{
    int ret = _register_ioctl_handler(my_ioctl_handler, CMD1, CMDX);
    if (ret) {
        fprintf(stderr, "failed to register my ioctl handler (%d)\n", ret);
        abort();
    }
}

/* Automatic unregistration of the ioctl handler with libc */
static void __attribute__ ((destructor)) my_ioctl_handler_uninit()
{
    _unregister_ioctl_handler(my_ioctl_handler);
}

Classification:

QNX Neutrino

Safety:  
Cancellation point Yes
Interrupt handler Yes
Signal handler Yes
Thread Yes