'\" te
.\"  Copyright 1989 AT&T
.\" Copyright (c) 1997, Sun Microsystems, Inc.  All Rights Reserved
.TH write 9E "28 Mar 1997" "SunOS 5.11" "Driver Entry Points"
.SH NAME
write \- write data to a device
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/errno.h>
#include <sys/open.h>
#include <sys/cred.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>

\fBint prefix\fR\fBwrite\fR(\fBdev_t\fR \fIdev\fR, \fBstruct uio *\fR\fIuio_p\fR, \fBcred_t *\fR\fIcred_p\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI). This entry point is optional. 
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIdev\fR \fR
.ad
.RS 11n
.rt  
Device number.
.RE

.sp
.ne 2
.mk
.na
\fB\fIuio_p\fR \fR
.ad
.RS 11n
.rt  
Pointer to the  \fBuio\fR(9S) structure that describes where the data is to be stored in user space.
.RE

.sp
.ne 2
.mk
.na
\fB\fIcred_p\fR \fR
.ad
.RS 11n
.rt  
Pointer to the  user credential structure for the \fBI/O \fRtransaction.
.RE

.SH DESCRIPTION
.sp
.LP
Used for character or raw data \fBI/O, \fRthe driver  \fBwrite()\fR routine is called indirectly through  \fBcb_ops\fR(9S) by the  \fBwrite\fR(2) system call.  The  \fBwrite()\fR routine supervises the data transfer from user space to a device described by the  \fBuio\fR(9S) structure.
.sp
.LP
The  \fBwrite()\fR routine should check the validity of the minor number component of  \fIdev\fR and the user credentials pointed to by \fIcred_p\fR, if pertinent.
.SH RETURN VALUES
.sp
.LP
The  \fBwrite()\fR routine should return \fB0\fR for success, or the appropriate error number.
.SH EXAMPLES
.sp
.LP
The following is an example of a \fBwrite()\fR routine using \fBphysio\fR(9F) to perform writes to a seekable device:
.sp
.in +2
.nf
static int
xxwrite(dev_t dev, struct uio *uiop, cred_t *credp)
{
      int	instance;
      xx_t	xx;

      instance = getminor(dev);
      xx = ddi_get_soft_state(xxstate, instance);
      if (xx == NULL)
             return (ENXIO);
      return (physio(xxstrategy, NULL, dev, B_WRITE,
             xxmin, uiop));
}
.fi
.in -2

.SH SEE ALSO
.sp
.LP
\fBread\fR(2), \fBwrite\fR(2), \fBread\fR(9E), \fBphysio\fR(9F), \fBcb_ops\fR(9S), \fBuio\fR(9S) 
.sp
.LP
\fIWriting Device Drivers for Oracle Solaris 11.2\fR