static int slcan_open(struct tty_struct *tty)
{
struct slcan *sl;
int err;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,25)
if (tty->ops->write == NULL)
return -EOPNOTSUPP;
#endif
/* RTnetlink lock is misused here to serialize concurrent
opens of slcan channels. There are better ways, but it is
the simplest one.
*/
rtnl_lock();
/* Collect hanged up channels. */
slc_sync();
sl = (struct slcan *) tty->disc_data;
err = -EEXIST;
/* First make sure we're not already connected. */
if (sl && sl->magic == SLCAN_MAGIC)
goto err_exit;
/* OK. Find a free SLCAN channel to use. */
err = -ENFILE;
/* Look to see if the user has requested a specific channel
* to be used (encoded as '0' plus the interface number requested in
* the otherwise unused swtch termios variable )
* stty swtch 'channel' device
* where 'channel' is '0' to maxdevs (0)
* where device is the name of the serial device (/dev/ttyUSB0)
*/
if ((SWTC_CHAR(tty)>='0') && (SWTC_CHAR(tty)<'0'+maxdev)){
sl = slc_alloc(tty_devnum(tty),SWTC_CHAR(tty));
} else {
/* OK. Find a free SLCAN channel to use. */
sl = slc_alloc(tty_devnum(tty),0);
}
if (sl == NULL)
goto err_exit;
sl->tty = tty;
tty->disc_data = sl;
sl->line = tty_devnum(tty);
sl->pid = current->pid;
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,16)
/* FIXME: already done before we were called - seems this can go */
if (tty->driver->flush_buffer)
tty->driver->flush_buffer(tty);
#endif
if (!test_bit(SLF_INUSE, &sl->flags)) {
/* Perform the low-level SLCAN initialization. */
sl->rcount = 0;
sl->xleft = 0;
set_bit(SLF_INUSE, &sl->flags);
err = register_netdevice(sl->dev);
if (err)
goto err_free_chan;
}
/* Done. We have linked the TTY line to a channel. */
rtnl_unlock();
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16)
tty->receive_room = 65536; /* We don't flow control */
#endif
return sl->dev->base_addr;
err_free_chan:
sl->tty = NULL;
tty->disc_data = NULL;
clear_bit(SLF_INUSE, &sl->flags);
err_exit:
rtnl_unlock();
/* Count references from TTY module */
return err;
}
static int slcan_open(struct tty_struct *tty)
{
struct slcan *sl;
int err;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
if (tty->ops->write == NULL)
return -EOPNOTSUPP;
/* RTnetlink lock is misused here to serialize concurrent
opens of slcan channels. There are better ways, but it is
the simplest one.
*/
rtnl_lock();
/* Collect hanged up channels. */
slc_sync();
sl = tty->disc_data;
err = -EEXIST;
/* First make sure we're not already connected. */
if (sl && sl->magic == SLCAN_MAGIC)
goto err_exit;
/* OK. Find a free SLCAN channel to use. */
err = -ENFILE;
sl = slc_alloc(tty_devnum(tty));
if (sl == NULL)
goto err_exit;
sl->tty = tty;
tty->disc_data = sl;
sl->line = tty_devnum(tty);
sl->pid = current->pid;
if (!test_bit(SLF_INUSE, &sl->flags)) {
/* Perform the low-level SLCAN initialization. */
sl->rcount = 0;
sl->xleft = 0;
set_bit(SLF_INUSE, &sl->flags);
err = register_netdevice(sl->dev);
if (err)
goto err_free_chan;
}
/* Done. We have linked the TTY line to a channel. */
rtnl_unlock();
tty->receive_room = 65536; /* We don't flow control */
/* TTY layer expects 0 on success */
return 0;
err_free_chan:
sl->tty = NULL;
tty->disc_data = NULL;
clear_bit(SLF_INUSE, &sl->flags);
err_exit:
rtnl_unlock();
/* Count references from TTY module */
return err;
}