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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 corresponding 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.
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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;
};
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