'\" te
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.TH POWER 9E "Sep 16, 2016"
.SH NAME
power \- power a device attached to the system
.SH SYNOPSIS
.nf
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBint prefix\fR\fBpower\fR(\fBdev_info_t\fR \fI*dip\fR, \fBint\fR \fIcomponent\fR, \fBint\fR \fIlevel\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI). This entry point is required. If the driver
writer does not supply this entry point, the value \fBNULL\fR must be used in
the \fBdev_ops\fR(9S) structure instead.
.SH PARAMETERS
.ne 2
.na
\fB\fIdip\fR\fR
.ad
.RS 13n
Pointer to the device's \fBdev_info\fR structure.
.RE

.sp
.ne 2
.na
\fB\fIcomponent\fR\fR
.ad
.RS 13n
Component of the driver to be managed.
.RE

.sp
.ne 2
.na
\fB\fIlevel\fR\fR
.ad
.RS 13n
Desired component power level.
.RE

.SH DESCRIPTION
The \fBpower\fR(9E) function is the device-specific Power Management entry
point. This function is called when the system wants the driver to set the
power level of \fIcomponent\fR to \fIlevel\fR.
.sp
.LP
The \fIlevel\fR argument is the driver-defined power level to which the
component needs to be set. Except for power level \fB0\fR, which is interpreted
by the framework to mean "powered off," the interpretation of \fIlevel\fR is
entirely up to the driver.
.sp
.LP
The \fIcomponent\fR argument is the component of the device to be
power-managed. The interpretation of \fIcomponent\fR is entirely up to the
driver.
.sp
.LP
When a requested power transition would cause the device to lose state, the
driver must save the state of the device in memory. When a requested power
transition requires state to be restored, the driver must restore that state.
.sp
.LP
If a requested power transition for one component requires another component to
change power state before it can be completed, the driver must call
\fBpm_raise_power\fR(9F) to get the other component changed, and the
\fBpower\fR(9E) entry point must support being re-entered.
.sp
.LP
If the system requests an inappropriate power transition for the device (for
example, a request to power down a device which has just become busy), then the
power level should not be changed and power should return \fBDDI_FAILURE\fR.
.SH RETURN VALUES
The \fBpower()\fR function returns:
.sp
.ne 2
.na
\fB\fBDDI_SUCCESS\fR\fR
.ad
.RS 15n
Successfully set the power to the requested \fIlevel\fR.
.RE

.sp
.ne 2
.na
\fB\fBDDI_FAILURE\fR\fR
.ad
.RS 15n
Failed to set the power to the requested \fIlevel\fR.
.RE

.SH CONTEXT
The \fBpower()\fR function is called from user or kernel context only.
.SH ATTRIBUTES
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface stability	Committed
.TE

.SH SEE ALSO
\fBattach\fR(9E), \fBdetach\fR(9E), \fBpm_busy_component\fR(9F),
\fBpm_idle_component\fR(9F), \fBpm_raise_power\fR(9F), \fBdev_ops\fR(9S)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fIUsing Power Management\fR