5.1.14 Registering the shutdown Routine
The following code shows how the
el_probe( )
routine registers its
shutdown( )
routine. The kernel calls this routine when the system shuts
down. The driver can specify an argument for the kernel to pass to the
routine at that time.
if (!sc->reprobe)
drvr_register_shutdown(el_shutdown, (void*)sc, DRVR_REGISTER);
1
return( ~ 0);
}
1
Registers the
shutdown( )
routine and directs the kernel to pass
a pointer to the driver’s
softc
data structure to the routine. The
shutdown( )
routine is important for those devices that perform
DMA-related operations.
5.2 Implementing the el_shutdown Routine
The driver’s
shutdown( )
routine shuts down the controller. The kernel
calls all registered
shutdown( )
routines when the system shuts down.
The
el_probe( )
routine registers a
shutdown( )
routine called
el_shutdown( )
. The
if_el
device driver implements the routine as
follows:
static void el_shutdown(struct el_softc *sc)
1
{
WRITE_CMD(sc, CMD_RESET);
2
DELAY(1000);
3
}
1
Specifies the argument that the kernel passes to the routine, which is a
pointer to the driver’s
el_softc
data structure. The driver specifies
this argument when it registers the
shutdown( )
routine in its
probe
interface.
2
Calls the
WRITE_CMD
macro to write data to the command port register.
In this call, the
el_softc
data structure for this 3Com 3C5x9 device
contains the I/O handle to reference the device’s command register. The
data to be written is the
CMD_RESET
bit, which resets the device.
3
Calls the
DELAY
macro to delay the execution of
el_shutdown( )
for 1
millisecond before continuing execution. This gives the reset command
time to complete.
5.3 Implementing the el_autosense_thread Routine
The
if_el
device driver implements a driver-specific routine called
el_autosense_thread( )
to determine the mode of the network interface.
The
el_probe( )
routine calls
el_autosense_thread( )
during device
autoconfiguration.
Implementing the Autoconfiguration Support Section (probe) 5–17
