Motorola MCP750 Specifications download pdf (Page 155)

Developing a Device Drive

10-9

Typically, the types of activities performed by a driver’s init() or start() routine are

as follows:

1. Find the adapter’s entry in the array of adapter structures keying on the

adapter type and adapter number.

2. Read the device’s bus I/O address, and map the device into virtual address

space via physmap(D3).

3. Probe for the presence of the adapter at that address by calling

badaddr(D3).

4. If the device is present:

• Initialize the hardware—typically by writing to control registers and

calling drv_usecwait(D3) to busy wait while the device resets.

• If appropriate, allocate an interrupt vector by calling

ivec_alloc(D3), and register the interrupt handler via

ivec_init(D3).

Allocate and initialize any necessary control and data structures and buffers by calling

kmem_alloc(D3).

Further, the order in which the device drivers are initialized is not important. In rare cases,

some devices must be initialized before others. For this purpose, you must specify this

order in the Master(4) conﬁguration ﬁles of the associated drivers.

To initialize dynamically linked device drivers, the system speciﬁes distinct optional entry

points and kernel support routines, including the _load(D2) routine. In general, these

are called when the driver is initially invoked in order to load it into the running system.

Refer to Chapter 13 (“Loadable Modules”) for information on dynamically loadable mod-

ules.

Note that these routines execute on a single processor, do not have any user context, and

cannot cause the process to sleep.

The Init Routine 10

Speciﬁcation

#include <sys/adapter.h>

void

init (void)

Return Values

None.

To get started, the name of the init() entry point must be specified in the driver’s

Master(4) conﬁguration ﬁle. Also the Sadapters(4) ﬁle must contain the hardware

attributes of the device.

You can take advantage of the fact that interrupts are disabled in the init() routine to

initialize your device without risk of receiving an inopportune device interrupt. In general,

all tasks that require the system services to be disabled must be coded in the init() rou-

1 2 ... 150 151 152 153 154 155 156 157 158 159 160 ... 343 344

No comments

Motorola MCP750 Specifications Page 155