Motorola MCP750 Specifications download pdf (Page 317)

Writing a User-Level Device Drive

17-41

Provide Debug and Status Information 17

You might want to provide the -d option to facilitate debugging. To support the -d

option, the device configuration program displays the values that the device register

region and the driver status region contain. The type of information that you choose to

provide depends upon the nature of the device and the driver.

Restore the Device to its Initial State 17

The purposes of the -x option are (1) to destroy the user-level device driver’s association

with a device and (2) to restore the device to its initial state as defined by the kernel device

driver. To support the -x option, the device configuration program must perform the

following functions:

• Disconnect the user-level interrupt process from the interrupt vector, and

remove the deﬁned interrupt vector connection, if applicable.

Use the ICON_DISC iconnect(3C) library routine call to perform this

function. The program must have the P_USERINT privilege.

• Detach and remove the driver status and device register regions.

• Remove global data structures that contain information about a particular

device and the locations of its driver status and device register regions.

• Restore important device registers to their initial state (for example,

interrupt vectors, interrupt-enabled ﬂags, and so on).

Debugging the Driver 17

You can debug most components of a user-level device driver by using one of the standard

user-level debuggers: adb(1), gdb(1),orNightView(1). You cannot use one of

these debuggers to debug the interrupt-handling routine, however, because it executes at

interrupt level; you can, instead, use the console processor to obtain some debugging

capability for this routine (refer to the PowerUX Real-Time Guide for an explanation of

the procedures for debugging the interrupt-handling routine).

A debugger uses ptrace(2) to access memory in the debugged process. If you use a

debugger to examine memory that is mapped to I/O memory addresses, you can cause the

system to panic. (For information on the ptrace(2) system call, refer to the

corresponding system manual page.)

When you are developing and debugging a user-level device driver, it is recommended that

you use the following techniques:

• Debug a user-level driver on a single-user system because it is possible for

the driver to cause the system to crash.

• Keep the work in the interrupt-handling routine to a minimum.

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Motorola MCP750 Specifications Page 317