Motorola MCP750 Specifications download pdf (Page 141)

Understanding the Kernel Environmen

9-21

device unit identiﬁer or a pointer to a conﬁguration structure. When the interrupt becomes

active, the interrupt handler parameter is passed as the ﬁrst and only parameter to the inter-

rupt routine.

Following is an example code fragment that shows how to allocate an interrupt vector and

associate an interrupt handler with that vector:

uint myhandlr_param;

extern void myintr_handlr(uint handlr_param);

* Allocate and initialize an interrupt vector

if ((i = ivec_alloc()) == -1 )

{

/* Attempt to obtain interrupt vector failed: return */

cmn_err(CE_WARN,

"mydriver: \

Can’t allocate an interrupt vector!\n");

return(FALSE);

}

/* Obtained interrupt vector successfully:

* Register an interrupt handler for the interrupt vector

ivec_init(i, &myintr_handlr, myhandlr_param);

Debug Routines 9

The kernel provides a very useful routine, cmn_err(D3), that allows you to send an

error message to the system console or the circular kernel buffer putbuf. This routine

can also be used during debugging to display a panic message and halt the system. For

additional information on the use of cmn_err, refer to Chapter 15, “Driver Testing and

Debugging.”

Small vs. Large Offset Drivers 9

Starting with PowerMAX OS 4.2, drivers may be compiled one of two ways: as large off-

set drivers or as small offset drivers.

The small offset driver is the traditional type of driver provided by the earlier revisions of

PowerMAX OS. These drivers are passed (and return) offsets which are of type off_t.

Since the off_t type is really a 32-bit integer type, small offset drivers cannot handle

devices (such as disk partitions) larger than 4 Gigabytes.

To handle today's newer and larger devices, the ability to create large offset drivers has

been introduced. A driver compiled as a large offset driver is given (and returns) 64-bit

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Motorola MCP750 Specifications Page 141