'\" te
.\" Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.
.\" Copyright 1989 AT&T
.TH timeout 9F "16 Jan 2006" "SunOS 5.11" "Kernel Functions for Drivers"
.SH NAME
timeout \- execute a function after a specified length of time
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/conf.h>

\fBtimeout_id_t\fR \fBtimeout\fR(\fBvoid (\fR\fI* func\fR)(void \fI*\fR), \fBvoid\fR \fI*arg\fR, 
     \fBclock_t\fR  \fIticks\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIfunc\fR\fR
.ad
.RS 9n
.rt  
Kernel function to invoke when the time increment expires.
.RE

.sp
.ne 2
.mk
.na
\fB\fIarg\fR\fR
.ad
.RS 9n
.rt  
Argument to the function.
.RE

.sp
.ne 2
.mk
.na
\fB\fIticks\fR\fR
.ad
.RS 9n
.rt  
Number of clock ticks to wait before the function is called. Use \fBdrv_usectohz\fR(9F) to convert microseconds to clock ticks.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBtimeout()\fR function schedules the specified function to be called after a specified time interval. The exact time interval over which the timeout takes effect cannot be guaranteed, but the value given is a close approximation.
.sp
.LP
The function called by \fBtimeout()\fR must adhere to the same restrictions as a driver soft interrupt handler.
.sp
.LP
The \fBdelay\fR(9F) function calls \fBtimeout()\fR. Because \fBtimeout()\fR is subject to priority inversion, drivers waiting on behalf of processes with real-time constraints should use \fBcv_timedwait\fR(9F) rather than \fBdelay()\fR.
.SH RETURN VALUES
.sp
.LP
The \fBtimeout()\fR function returns an opaque non-zero \fBtimeout\fR identifier that can be passed to \fBuntimeout\fR(9F) to cancel the request.
.SH CONTEXT
.sp
.LP
The \fBtimeout()\fR function can be called from user, interrupt, or kernel context.
.SH EXAMPLES
.LP
\fBExample 1 \fRUsing \fBtimeout()\fR
.sp
.LP
In the following example, the device driver has issued an IO request and is waiting for the device to respond. If the device does not respond within 5 seconds, the device driver will print out an error message to the console.

.sp
.in +2
.nf
static void
xxtimeout_handler(void *arg)
{
        struct xxstate *xsp = (struct xxstate *)arg;
        mutex_enter(&xsp->lock);
        cv_signal(&xsp->cv);
        xsp->flags |= TIMED_OUT;
        mutex_exit(&xsp->lock);
        xsp->timeout_id = 0;
}
static uint_t
xxintr(caddr_t arg)
{
        struct xxstate *xsp = (struct xxstate *)arg;
         .
         .
         .
        mutex_enter(&xsp->lock);
        /* Service interrupt */
        cv_signal(&xsp->cv);
        mutex_exit(&xsp->lock);
        if (xsp->timeout_id != 0) {
                (void) untimeout(xsp->timeout_id);
                xsp->timeout_id = 0;
        }
        return(DDI_INTR_CLAIMED);
}
static void
xxcheckcond(struct xxstate *xsp)
{
         .
         .
         .
        xsp->timeout_id = timeout(xxtimeout_handler,
            xsp, (5 * drv_usectohz(1000000)));
        mutex_enter(&xsp->lock);
        while (/* Waiting for interrupt  or timeout*/)
                cv_wait(&xsp->cv, &xsp->lock);
        if (xsp->flags & TIMED_OUT)
                cmn_err(CE_WARN, "Device not responding");
         .
         .
         .
        mutex_exit(&xsp->lock);
         .
         .
         .
}   
.fi
.in -2

.SH SEE ALSO
.sp
.LP
\fBbufcall\fR(9F), \fBcv_timedwait\fR(9F), \fBddi_in_panic\fR(9F), \fBdelay\fR(9F), \fBdrv_usectohz\fR(9F), \fBuntimeout\fR(9F) 
.sp
.LP
\fIWriting Device Drivers for Oracle Solaris 11.2\fR