NAME

drv_getparm − retrieve kernel state information

SYNOPSIS

#include <sys/ddi.h>
int drv_getparm(unsigned int parm, void ∗value_p);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI). 

ARGUMENTS

parm The kernel parameter to be obtained.  Possible values are:

LBOLT Read the value of lbolt.  lbolt is an integer that is unconditionally incremented by one at each clock tick.  No special treatment is applied when this value overflows the maximum value of a signed int.  When this occurs, its value will be negative, and its magnitude will be decreasing until it again passes zero.  It can therefore not be relied upon to provide an indication of the amount of time that passes since the last system reboot, nor should it be used to mark an absolute time in the system.  Only the difference between two measurements of lbolt is significant.  It is used in this way inside the system kernel for timing purposes. 

PPGRP Read the process group identification number.  This number determines which processes should receive a HANGUP or BREAK signal when detected by a driver. 

UPROCP Read the process table token value. 

PPID Read process identification number. 

PSID Read process session identification number. 

TIME Read time in seconds. 

UCRED Return a pointer to the caller’s credential structure. 

value_p A pointer to the data space in which the value of the parameter is to be copied. 

DESCRIPTION

drv_getparm() function verifies that parm corresponds to a kernel parameter that may be read.  If the value of parm does not correspond to a parameter or corresponds to a parameter that may not be read, -1 is returned.  Otherwise, the value of the parameter is stored in the data space pointed to by value_p.

drv_getparm() does not explicitly check to see whether the device has the appropriate context when the function is called and the function does not check for correct alignment in the data space pointed to by value_p. It is the responsibility of the driver writer to use this function only when it is appropriate to do so and to correctly declare the data space needed by the driver.

RETURN VALUES

drv_getparm() returns 0 to indicate success, −1 to indicate failure.  The value stored in the space pointed to by value_p is the value of the parameter if 0 is returned, or undefined if −1 is returned.  −1 is returned if you specify a value other than LBOLT, PPGRP, PPID, PSID, TIME, UCRED, or UPROCP.  Always check the return code when using this function. 

CONTEXT

drv_getparm() can be called from user context only when using PPGRP, PPID, PSID, UCRED, or UPROCP.  It can be called from user or interrupt context when using the LBOLT or TIME argument. 

SEE ALSO

buf(9S)

Writing Device Drivers

SunOS 5.6  —  Last change: 24 Jun 1997