Motorola MCP750 Specifications download pdf (Page 295)

Writing a User-Level Device Drive

17-19

is suggested that the string indicate the name of the routine that has produced

the error.

The uderror routine writes the following to the standard error: the specified string,

followed by a colon, a space, a brief error message corresponding to the specified error

code, and a newline. Examples of the call and resulting output are as follows:

uderror(EUD_MEMLOCK,”lock_driver_pages”);

"lock_driver_pages: unable to lock driver text pages"

An array of pointers to the error messages associated with the user-level device driver

error codes, ud_errmsg, is defined and initialized in the file <userdriv.h>. You can

index the ud_errmsg array by using a user-level device driver error code. The variable

udmaxerr contains the highest message number that can be used to index the array.

For reference information on the uderror(3X) routine, refer to the corresponding sys-

tem manual page.

The spl Support Routines 17

A set of C library routines enables you to raise and lower a processor’s interrupt priority

level from user level. You can modify the IPL by binding the physical address of the IPL

ter. The routines and macro are brieﬂy described as follows:

spl_map map the physical address of the IPL register

or processor level register to a process’s vir-

tual address space

spl_request set the processor IPL to a speciﬁed level

spl_request_macro set the processor IPL to a speciﬁed level

spl_unmap unmap the IPL register or processor level

The spl support routines are used to synchronize processes’ access to device registers,

synchronize processes’ access to shared data that can be modified at program and interrupt

level, and prevent rescheduling while a spin lock is locked.

Procedures for using the routines and the related macro are fully explained in the Pow-

erUX Real-Time Guide; reference information is provided in the corresponding system

manual pages.

Process Synchronization Tools 17

A set of real-time process synchronization tools has been developed to provide solutions

to the problems associated with synchronizing cooperating processes’ access to data in

shared memory. They include tools for controlling a process’s vulnerability to

rescheduling, serializing processes’ access to critical sections with busy-wait mutual

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Motorola MCP750 Specifications Page 295