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() 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() from their power(9E) function before powering-off a device. If pm_trans_check() 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() 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  time-
       out(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

       1     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	     |Committed 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

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

       Writing Device Drivers

       Using Power Management

SunOS 5.11							    16 Oct 1999 						pm_trans_check(9F)