you call
simple_unlock( )
to release it. Because simple locks are spin
locks,
simple_lock( )
does not return until the lock has been obtained.
12.4 Enabling Loopback Mode (SIOCENABLBACK ioctl
Command)
The following code shows how the
el_ioctl( )
routine implements the
SIOCENABLBACK ioctl
command to enable loopback mode when an
application requests it. Support for the
SIOCENABLBACK
command is
optional. You can choose whether or not your driver supports it.
switch (cmd) {
1
case SIOCENABLBACK:
2
ifp->if_flags |= IFF_LOOPBACK;
3
if (ifp->if_flags & IFF_RUNNING)
4
el_reset_locked(sc, ifp, unit);
break;
1
Evaluates the value passed in through the
cmd
argument to determine
which
ioctl
command the caller has requested.
2
Determines whether the
cmd
argument is
SIOCENABLBACK
.
3
Sets the
IFF_LOOPBACK
bit in the
if_flags
member of the
ifnet
data
structure for this device.
4
If the device is running, calls the
el_reset_locked( )
routine to
restart the network interface in loopback mode.
12.5 Disabling Loopback Mode (SIOCDISABLBACK ioctl
Command)
The following code shows how the
el_ioctl( )
routine implements the
SIOCDISABLBACK ioctl
command to disable loopback mode when an
application requests it. Support for the
SIOCDISABLBACK
command is
optional. However, if your driver supports
SIOCENABLBACK
, it must support
SIOCDISABLBACK
.
case SIOCDISABLBACK:
1
ifp->if_flags &=
~IFF_LOOPBACK;
2
if (ifp->if_flags & IFF_RUNNING)
3
el_reset_locked(sc, ifp, unit);
break;
1
Determines whether the
cmd
argument is
SIOCDISABLBACK
.
2
Clears the
IFF_LOOPBACK
bit in the
if_flags
member of the
ifnet
data structure for this device.
3
If the device is running, calls the
el_reset_locked( )
routine.
The
el_reset_locked( )
routine calls
el_init_locked( )
, which
restarts the network interface in normal mode.
12–4 Implementing the ioctl Section
