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

NAME

       pm_trans_check -  Device power cycle advisory check

SYNOPSIS

       #include <sys/sunddi.h>

       int pm_trans_check(struct pm_trans_data *datap, time_t *intervalp);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI)

PARAMETERS

       datap	       Pointer to a pm_trans_data structure

       intervalp       Pointer to time difference when next power cycle will be advised

DESCRIPTION

       The  pm_trans_check(9F) function checks if a power-cycle is currently advised based on data in the pm_trans_data  structure.  This function
       is provided to prevent damage to devices from excess power cycles; drivers for devices that are sensitive to the  number  of  power  cycles
       should  call pm_trans_check(9F) from their power(9E) function before powering-off a device. If pm_trans_check(9F) indicates that the device
       should not be power cycled, the driver should not attempt to power cycle the device and should fail the call to power(9E) entry point.

       If pm_trans_check(9F) returns that it is not advised to power cycle the device, it attempts to calculate when  the   next  power  cycle	is
       advised,  based on the supplied parameters. In such case, intervalp  returns the time difference (in seconds) from the current time to when
       the next power cycle is advised. If the time for the next power cycle cannot be determined, intervalp  indicates 0.

       To avoid excessive calls to the power(9E) entry point during a period when power cycling is not advised, the driver should mark the  corre-
       sponding  device component busy for the	intervalp   time period (if interval is not 0). Conveniently, the driver can utilize the fact that
       calls to pm_busy_component(9F) are stacked. If power cycling is not advised, the driver can call pm_busy_component(9F)
	and issue a timeout(9F) for the intervalp   time. The timeout() handler can issue the corresponding pm_idle_component(9F) call.

       When the format field of  pm_trans_data is set to DC_SCSI_FORMAT, the caller must  provide valid data in svc_date[], lifemax, and  ncycles.
       Currently, flag must be set to 0.

       struct pm_scsi_cycles {
		 int lifemax;			    /* lifetime max power cycles */
		 int ncycles;			    /* number of cycles so far */
		 char svc_date[DC_SCSI_MFR_LEN];    /* service date YYYYWW */
		 int flag;			    /* reserved for future */
	    };

	    struct pm_trans_data {
		 int format;			    /* data format */
		 union {
		      struct pm_scsi_cycles scsi_cycles;
		 } un;
	    };

RETURN VALUES

       "small and bold">Power cycle is advised

       0		Power cycle is not advised

       -1		Error due to invalid argument.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

	 power.conf(4),  attributes(5),  power(9E)

       Writing Device Drivers

       Using Power Management

SunOS 5.10							    16 Oct 1999 						pm_trans_check(9F)