'\" te
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.TH kstat_io 9S "4 Apr 1994" "SunOS 5.11" "Data Structures for Drivers"
.SH NAME
kstat_io \- structure for I/O kstats
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/kstat.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
.fi

.SH INTERFACE LEVEL
.sp
.LP
Solaris DDI specific (Solaris DDI)
.SH DESCRIPTION
.sp
.LP
I/O kstat statistics are kept in a \fBkstat_io\fR structure. When
\fBkstat_create\fR(9F) creates an \fBI/O\fR \fBkstat\fR, the \fBks_data\fR
field is a pointer to one of these structures. The macro \fBKSTAT_IO_PTR()\fR
is provided to retrieve this field. It looks like this:
.sp
.in +2
.nf
#define KSTAT_IO_PTR(kptr)	((kstat_io_t *)(kptr)->ks_data)
.fi
.in -2

.SH STRUCTURE MEMBERS
.sp
.in +2
.nf
u_longlong_t      nread;      /* number of bytes read */
u_longlong_t      nwritten;   /* number of bytes written *]/
ulong_t           reads;      /* number of read operations */
ulong_t           writes;     /* number of write operations */
.fi
.in -2

.sp
.LP
The \fBnread\fR field should be updated by the driver with the number of bytes
successfully read upon completion.
.sp
.LP
The \fBnwritten\fR field should be updated by the driver with the number of
bytes successfully written upon completion.
.sp
.LP
The \fBreads\fR field should be updated by the driver after each successful
read operation.
.sp
.LP
The \fBwrites\fR field should be updated by the driver after each successful
write operation.
.sp
.LP
Other \fBI/O\fR statistics are updated through the use of the
\fBkstat_queue\fR(9F) functions.
.SH SEE ALSO
.sp
.LP
\fBkstat_create\fR(9F), \fBkstat_named_init\fR(9F), \fBkstat_queue\fR(9F),
\fBkstat_runq_back_to_waitq\fR(9F), \fBkstat_runq_enter\fR(9F),
\fBkstat_runq_exit\fR(9F), \fBkstat_waitq_enter\fR(9F),
\fBkstat_waitq_exit\fR(9F), \fBkstat_waitq_to_runq\fR(9F)
.sp
.LP
\fIWriting Device Drivers\fR