drv_getparm(9f) [linux man page]

drv_getparm(9F) 					   Kernel Functions for Drivers 					   drv_getparm(9F)

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).

PARAMETERS

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

       "small and bold"ReadLTthe  value  of  lbolt.  lbolt is a clock_t that is unconditionally incremented by one at each clock tick.	No special
		       treatment is applied when this value overflows the maximum value of the signed integral type clock_t. 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

       Since  the  release  of	the  Solaris  2.6  operating  environment,  the  drv_getparm()	function  has  been replaced by ddi_get_lbolt(9F),
       ddi_get_time(9F), and ddi_get_pid(9F).

       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

       ddi_get_lbolt(9F), ddi_get_pid(9F), ddi_get_time(9F),  buf(9S)

       Writing Device Drivers

SunOS 5.10							    24 Jun 1997 						   drv_getparm(9F)

Check Out this Related Man Page

drv_usectohz(9F)					   Kernel Functions for Drivers 					  drv_usectohz(9F)

NAME

       drv_usectohz - convert microseconds to clock ticks

SYNOPSIS

       #include <sys/types.h>
       #include <sys/ddi.h>

       clock_t drv_usectohz(clock_t microsecs);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       microsecs    The number of microseconds to convert.

DESCRIPTION

       The  drv_usectohz()  function  converts a length of time expressed in microseconds to a number of system clock ticks. The time arguments to
       timeout(9F) and delay(9F) are expressed in clock ticks.

       The drv_usectohz() function is a portable interface for drivers to make calls to timeout(9F) and delay(9F)  and	remain	binary	compatible
       should the driver object file be used on a system with a different clock speed (a different number of ticks in a second).

RETURN VALUES

       The  value returned is the number of system clock ticks equivalent to the microsecs argument. No error value is returned. If the clock tick
       equivalent to microsecs is too large to be represented as a clock_t, then the maximum clock_t value will be returned.

CONTEXT

       The drv_usectohz() function can be called from user, interrupt, or kernel context.

SEE ALSO

       delay(9F), drv_hztousec(9F), timeout(9F)

       Writing Device Drivers

NOTES

       If the microsecs argument to drv_usectohz() is less than drv_hztousec(9F), drv_usectohz() returns one tick. This, coupled with  multiplica-
       tion,  can result in significantly longer durations than expected. For example, on a machine where hz is 100, calling drv_usectohz() with a
       microsecs value less than 10000 returns a result equivalent to 10000 (1 tick). This type of mistake causes code such  as"5000  *  drv_usec-
       tohz(1000)" to compute a duration of 50 seconds instead of the intended 5 seconds.

SunOS 5.11							    24 Apr 2008 						  drv_usectohz(9F)

Linux and UNIX Man Pages

drv_getparm(9f) [linux man page]

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