This is smbmsg(8), a small utility to send/receive SMBus messages.

Also included is a `bus-probe' modus of operation to help scanning
an I2C bus.

4 files changed, 662 insertions, 0 deletions

diff --git a/usr.sbin/smbmsg/Makefile b/usr.sbin/smbmsg/Makefile
new file mode 100644
index 0000000..1fc7d3e
--- /dev/null
+++ b/usr.sbin/smbmsg/Makefile
@@ -0,0 +1,8 @@
+#
+# $FreeBSD$
+
+PROG=	smbmsg
+MAN8=	smbmsg.8
+WARNS=	6
+
+.include <bsd.prog.mk>
diff --git a/usr.sbin/smbmsg/pathnames.h b/usr.sbin/smbmsg/pathnames.h
new file mode 100644
index 0000000..aff7335
--- /dev/null
+++ b/usr.sbin/smbmsg/pathnames.h
@@ -0,0 +1,29 @@
+/*-
+ * Copyright (C) 2004 Joerg Wunsch
+ * All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#define PATH_DEFAULTSMBDEV	"/dev/smb0"
diff --git a/usr.sbin/smbmsg/smbmsg.8 b/usr.sbin/smbmsg/smbmsg.8
new file mode 100644
index 0000000..f25da7b
--- /dev/null
+++ b/usr.sbin/smbmsg/smbmsg.8
@@ -0,0 +1,286 @@
+.\" Copyright (c) 2004 Joerg Wunsch
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd May 16, 2004
+.Dt SMBMSG 8
+.Os
+.Sh NAME
+.Nm smbmsg
+.Nd "send or receive messages over an SMBus"
+.Sh SYNOPSIS
+.Nm
+.Op Fl f Ar dev
+.Fl p
+.Pp
+.Nm
+.Op Fl f Ar dev
+.Fl s Ar slave
+.Op Fl F Ar fmt
+.Op Fl c Ar cmd
+.Op Fl w
+.Op Fl i Ar incnt
+.Op Fl o Ar outcnt
+.Op Ar outdata ...
+.Sh DESCRIPTION
+The
+.Nm
+command can be used to send or receive messages over an
+SMBus, see
+.Xr smbus 4 .
+.Pp
+The
+.Nm
+command has two different modi of operation.
+The first form shown in the synopsis can be used to
+.Dq probe
+the devices on the SMBus.
+This is done by sending each valid device address one
+receive byte, and one quick read message, respectively.
+Devices that respond to these requests will by displayed
+by their device address, followed by the strings
+.Ql r ,
+.Ql w ,
+or
+.Ql rw ,
+for devices that are readable, writeable, or both, readable
+and writeable, respectively.
+The only valid additional option for this modus of operation (besides
+the
+.Fl p
+option that choses the modus) is
+.Fl f Ar dev .
+See below for a description.
+.Pp
+Note that probing the bus is risky, since individual devices could
+perform unwanted actions upon receiving one of the mentioned messages.
+For example, if a particular SMBus device considers
+.Em any
+write operation issued to it as a request to power off the system,
+the probing would trigger this action.
+.Pp
+The second form shown in the synopsis can be used to send or receive
+arbitrary messages to or from individual devices.
+This might be useful to explore individual devices on the SMBus, or
+maybe even to write short shell scripts performing maintenance
+operations on the bus.
+.Pp
+Any data values on the command-line are integer values in the
+range 0 through 255 for byte values, or 0 through 65535 for
+word values.
+They can be specified using standard
+.Ql C
+notation (prefix 0 for octal interpretation, or 0x for
+hexadecimal interpretation).
+.Pp
+Since the low-order bit of the device address of SMBus devices
+selects between read and write operations, only even-numbered
+slave addresses can exist on the bus.
+.Pp
+The options are as follows:
+.Bl -tag -width ".Fl o Ar outcnt"
+.It Fl F Ar fmt
+Specify the
+.Xr printf 3
+format to be used for displaying input data.
+This option is ignored in messages that do not read any input
+from the SMBus device.
+The format defaults to
+.Ql 0x%02x
+for byte input operations, and to
+.Ql 0x%04x
+for word input operations.
+For multi-byte input (block read), the same format is used for
+each individual byte read from the SMBus.
+.It Fl c Ar cmd
+This is the value of the
+.Em command
+byte to be issued as part of the SMBus message.
+.It Fl f Ar dev
+This specifies that
+.Ar dev
+should be used as the connection to the SMBus, rather than the
+default of
+.Pa /dev/smb0 .
+.It Fl i Ar incnt
+An SMBus message should be generated to read
+.Ar incnt
+bytes from the device.
+.It Fl o Ar outcnt
+An SMBus message should be generated to write
+.Ar outcnt
+bytes to the device.
+The data values to write are expected to follow all of the options
+(and their arguments) on the command-line, where the number of data
+bytes must match the
+.Ar outcnt
+value.
+.It Fl p
+This selects the
+.Em probe bus
+modus of operation.
+.It Fl s Ar slave
+The
+.Ar slave
+parameter specifies which SMBus device to connect to.
+This option also selects the
+.Em transfer messages from/to device
+modus of operation, where a slave address is mandatory.
+.It Fl w
+This option specifies that IO operations are word operations,
+rather than byte operations.
+Either
+.Ar incnt ,
+or
+.Ar outcnt
+(or both) must be equal 2 in this case.
+Note that the SMBus byte order is defined to be little-endian
+(low byte first, high byte follows).
+.El
+.Pp
+Not all argument combinations make sense in order to form valid SMBus
+messages.
+If no
+.Fl c Ar cmd
+option has been provided, the following messages can be
+issued:
+.Pp
+.Bd -unfilled -offset indent
+.TS
+l r r.
+\fBmessage	incnt	outcnt\fR
+quick read	0	\&-
+quick write	\&-	0
+receive byte	1	\&-
+send byte	\&-	1
+.TE
+.Ed
+.Pp
+Note in particular that specifying 0 as a count value
+has a different meaning than omitting the respective
+option entirely.
+.Pp
+If a command value has been given using the
+.Fl c Ar cmd
+option, the following messages can be generated:
+.Pp
+.Bd -unfilled -offset indent
+.TS
+l l r r.
+\fBmessage	\&-w	incnt	outcnt\fR
+read byte	no	1	\&-
+write byte	no	\&-	1
+read word	yes	2	\&-
+write word	yes	\&-	2
+process call	yes	2	2
+block read	no	\*(Ge 2	\&-
+block write	no	\&-	\*(Ge 2
+.TE
+.Ed
+.Sh FILES
+.Bl -tag -width ".Pa /dev/smb0" -compact
+.It Pa /dev/smb0
+The default device to connect to, unless
+.Fl f Ar dev
+has been provided.
+.El
+.Sh EXAMPLES
+Typical usage examples of the
+.Nm
+command include:
+.Pp
+.Dl "smbmsg -f /dev/smb1 -p"
+.Pp
+Probe all devices on the SMBus attached to
+.Pa /dev/smb1 .
+.Pp
+.Dl "smbmsg -s 0x70 -i 1"
+.Pp
+Issue a
+.Em receive byte
+message to the device at address 0x70, and display
+the received byte using the default format.
+.Pp
+.Dl "smbmsg -s 0x70 -c 0xff -i 1 -F %d"
+.Pp
+Issue a
+.Em read byte
+message to the device at slave address 0x70, using
+255 (0xff) as the command-byte to send to the device,
+and display the result using the custom format %d.
+.Pp
+.Dl "smbmsg -s 0xa0 -c 0 -o 1 0x80"
+.Pp
+Send a
+.Em write byte
+message to the slave device at address 0xa0, using
+0 as the command-byte value, and 0x80 as the byte to
+send (after the command).
+Assuming this might be a Philips PCF8583 real-time clock,
+this would stop the clock.
+.Pp
+.Dl "smbmsg -s 0xa0 -c 1 -i 6 -F %02x"
+.Pp
+Send a
+.Em block read
+command to device at address 0xa0, and read 6 bytes from
+it, using hexadecimal display.
+Again, assuming a PCF8583 RTC, this would display the
+fractions of second, seconds, minutes, hours, year/date,
+and weekday/month values.
+Since this RTC uses BCD notation, the actual values displayed
+were decimal then.
+.Pp
+.Dl "smbmsg -s 0xa0 -c 2 -o 5 0x00 0x07 0x22 0x16 0x05"
+.Pp
+Send a
+.Em block write
+command to device at address 0xa0.
+For the PCF8583 RTC, this would set the clock to Sunday (2004%4)-05-16
+22:07:00.
+.Sh DIAGNOSTICS
+Exit status is 0 on success, or according to
+.Xr sysexits 3
+in case of failure.
+Diagnostic messages issued are supposed to be self-explanatory.
+.Sh SEE ALSO
+.Xr printf 3 ,
+.Xr sysexits 3 ,
+.Xr smb 4 ,
+.Xr smbus 4
+.Rs
+.%T "The SMBus specification"
+.%O http://www.smbus.org/specs/
+.Re
+.Sh HISTORY
+The
+.Nm
+command first appeared in
+.Fx 5.3 .
+.Sh AUTHORS
+The
+.Nm
+utility and this manual page were written by
+.An J\(:org Wunsch .
diff --git a/usr.sbin/smbmsg/smbmsg.c b/usr.sbin/smbmsg/smbmsg.c
new file mode 100644
index 0000000..6d1ca94
--- /dev/null
+++ b/usr.sbin/smbmsg/smbmsg.c
@@ -0,0 +1,339 @@
+/*-
+ * Copyright (C) 2004 Joerg Wunsch
+ * All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Send or receive messages over an SMBus.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/ioctl.h>
+
+#include <dev/smbus/smb.h>
+
+#include "pathnames.h"
+
+static const char *dev = PATH_DEFAULTSMBDEV;
+static const char *bytefmt = "0x%02x";
+static const char *wordfmt = "0x%04x";
+static const char *fmt;
+
+static int fd;			/* file descriptor for /dev/smbX */
+static int cflag = -1;		/* SMBus cmd */
+static int iflag = -1;		/* input data */
+static int oflag = -1;		/* output data */
+static int pflag;		/* probe bus */
+static int slave = -1;		/* slave address */
+static int wflag;		/* word IO */
+
+static unsigned char ibuf[SMB_MAXBLOCKSIZE];
+static unsigned char obuf[SMB_MAXBLOCKSIZE];
+static unsigned short oword, iword;
+
+/*
+ * The I2C specs say that all addresses below 16 and above or equal
+ * 240 are reserved.  Address 0 is the global address, but we do not
+ * care for this detail.
+ */
+#define MIN_I2C_ADDR	16
+#define MAX_I2C_ADDR	240
+
+static void
+usage(void)
+{
+	fprintf(stderr,
+		"usage: smbmsg [-f dev] -p\n"
+		"       smbmsg [-f dev] -s slave [-F fmt] [-c cmd] [-w] "
+		"[-i incnt] [-o outcnt] [outdata ...]\n");
+	exit (EX_USAGE);
+}
+
+static int
+getnum(const char *s)
+{
+	char *endp;
+	unsigned long l;
+
+	l = strtoul(s, &endp, 0);
+	if (*s != '\0' && *endp == '\0')
+		return (int)l;
+	return -1;
+}
+
+static void
+probe_i2c(void)
+{
+	unsigned char addr;
+	int flags;
+#define IS_READABLE	1
+#define IS_WRITEABLE	2
+	struct smbcmd c;
+
+	printf("Probing for devices on %s:\n", dev);
+
+	for (addr = MIN_I2C_ADDR; addr < MAX_I2C_ADDR; addr += 2) {
+		c.slave = addr;
+		flags = 0;
+		if (ioctl(fd, SMB_RECVB, &c) != -1)
+			flags = IS_READABLE;
+		if (ioctl(fd, SMB_QUICK_WRITE, &c) != -1)
+			flags |= IS_WRITEABLE;
+		if (flags != 0) {
+			printf("Device @0x%02x: ", addr);
+			if (flags & IS_READABLE)
+				putchar('r');
+			if (flags & IS_WRITEABLE)
+				putchar('w');
+			putchar('\n');
+		}
+	}
+}
+
+static int
+do_io(void)
+{
+	struct smbcmd c;
+	int i;
+
+	c.slave = slave;
+	c.cmd = cflag;
+
+	if (fmt == NULL && iflag > 0)
+		fmt = wflag? wordfmt: bytefmt;
+
+	if (cflag == -1) {
+		/* operations that do not require a command byte */
+		if (iflag == -1 && oflag == 0)
+			/* 0 bytes output: quick write operation */
+			return (ioctl(fd, SMB_QUICK_WRITE, &c));
+		else if (iflag == 0 && oflag == -1)
+			/* 0 bytes input: quick read operation */
+			return (ioctl(fd, SMB_QUICK_READ, &c));
+		else if (iflag == 1 && oflag == -1) {
+			/* no command, 1 byte input: receive byte op. */
+			if (ioctl(fd, SMB_RECVB, &c) == -1)
+				return (-1);
+			printf(fmt, (unsigned char)c.cmd);
+			putchar('\n');
+			return (0);
+		} else if (iflag == -1 && oflag == 1) {
+			/* no command, 1 byte output: send byte op. */
+			c.cmd = obuf[0];
+			return (ioctl(fd, SMB_SENDB, &c));
+		} else
+			return (-2);
+	}
+	if (iflag == 1 && oflag == -1) {
+		/* command + 1 byte input: read byte op. */
+		c.data.byte_ptr = ibuf;
+		if (ioctl(fd, SMB_READB, &c) == -1)
+			return (-1);
+		printf(fmt, (int)(unsigned char)ibuf[0]);
+		putchar('\n');
+		return (0);
+	} else if (iflag == -1 && oflag == 1) {
+		/* command + 1 byte output: write byte op. */
+		c.data.byte = obuf[0];
+		return (ioctl(fd, SMB_WRITEB, &c));
+	} else if (wflag && iflag == 2 && oflag == -1) {
+		/* command + 2 bytes input: read word op. */
+		c.data.word_ptr = &iword;
+		if (ioctl(fd, SMB_READW, &c) == -1)
+			return (-1);
+		printf(fmt, (int)(unsigned short)iword);
+		putchar('\n');
+		return (0);
+	} else if (wflag && iflag == -1 && oflag == 2) {
+		/* command + 2 bytes output: write word op. */
+		c.data.word = oword;
+		return (ioctl(fd, SMB_WRITEW, &c));
+	} else if (wflag && iflag == 2 && oflag == 2) {
+		/*
+		 * command + 2 bytes output + 2 bytes input:
+		 * "process call" op.
+		 */
+		c.data.process.sdata = oword;
+		c.data.process.rdata = &iword;
+		if (ioctl(fd, SMB_PCALL, &c) == -1)
+			return (-1);
+		printf(fmt, (int)(unsigned short)iword);
+		putchar('\n');
+		return (0);
+	} else if (iflag > 1 && oflag == -1) {
+		/* command + > 1 bytes of input: block read */
+		c.data.byte_ptr = ibuf;
+		c.count = iflag;
+		if (ioctl(fd, SMB_BREAD, &c) == -1)
+			return (-1);
+		for (i = 0; i < iflag; i++) {
+			if (i != 0)
+				putchar(' ');
+			printf(fmt, ibuf[i]);
+		}
+		putchar('\n');
+		return (0);
+	} else if (iflag == -1 && oflag > 1) {
+		/* command + > 1 bytes of output: block write */
+		c.data.byte_ptr = obuf;
+		c.count = oflag;
+		return (ioctl(fd, SMB_BWRITE, &c));
+	}
+
+	return (-2);
+}
+
+
+int
+main(int argc, char **argv)
+{
+	int i, n, errs = 0;
+	int savederrno;
+
+	while ((i = getopt(argc, argv, "F:c:f:i:o:ps:w")) != -1)
+		switch (i) {
+		case 'F':
+			fmt = optarg;
+			break;
+
+		case 'c':
+			if ((cflag = getnum(optarg)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", optarg);
+			if (cflag < 0 || cflag >= 256)
+				errx(EX_USAGE,
+				     "CMD out of range: %d",
+				     cflag);
+			break;
+
+		case 'f':
+			dev = optarg;
+			break;
+
+		case 'i':
+			if ((iflag = getnum(optarg)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", optarg);
+			if (iflag < 0 || iflag >= SMB_MAXBLOCKSIZE)
+				errx(EX_USAGE,
+				     "# input bytes out of range: %d",
+				     iflag);
+			break;
+
+		case 'o':
+			if ((oflag = getnum(optarg)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", optarg);
+			if (oflag < 0 || oflag >= SMB_MAXBLOCKSIZE)
+				errx(EX_USAGE,
+				     "# output bytes out of range: %d",
+				     oflag);
+			break;
+
+		case 'p':
+			pflag = 1;
+			break;
+
+		case 's':
+			if ((slave = getnum(optarg)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", optarg);
+
+			if (slave < MIN_I2C_ADDR || slave >= MAX_I2C_ADDR)
+				errx(EX_USAGE,
+				     "Slave address out of range: %d",
+				     slave);
+			break;
+
+		case 'w':
+			wflag = 1;
+			break;
+
+		default:
+			errs++;
+		}
+	argc -= optind;
+	argv += optind;
+	if (errs || (slave != -1 && pflag) || (slave == -1 && !pflag))
+		usage();
+	if (wflag &&
+	    !((iflag == 2 && oflag == -1) ||
+	      (iflag == -1 && oflag == 2) ||
+	      (iflag == 2 && oflag == 2)))
+		errx(EX_USAGE, "Illegal # IO bytes for word IO");
+	if (!pflag && iflag == -1 && oflag == -1)
+		errx(EX_USAGE, "Nothing to do");
+	if (pflag && (cflag != -1 || iflag != -1 || oflag != -1 || wflag != 0))
+		usage();
+	if (oflag > 0) {
+		if (oflag == 2 && wflag) {
+			if (argc == 0)
+				errx(EX_USAGE, "Too few arguments for -o count");
+			if ((n = getnum(*argv)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", *argv);
+			if (n < 0 || n >= 65535)
+				errx(EX_USAGE, "Value out of range: %d", n);
+			oword = n;
+			argc--;
+			argv++;
+		} else for (i = 0; i < oflag; i++, argv++, argc--) {
+			if (argc == 0)
+				errx(EX_USAGE, "Too few arguments for -o count");
+			if ((n = getnum(*argv)) == -1)
+				errx(EX_USAGE, "Invalid number: %s", *argv);
+			if (n < 0 || n >= 256)
+				errx(EX_USAGE, "Value out of range: %d", n);
+			obuf[i] = n;
+		}
+	}
+	if (argc != 0)
+		usage();
+
+	if ((fd = open(dev, O_RDWR)) == -1)
+		err(EX_UNAVAILABLE, "Cannot open %s", dev);
+
+	i = 0;
+	if (pflag)
+		probe_i2c();
+	else
+		i = do_io();
+
+	savederrno = errno;
+	close(fd);
+	errno = savederrno;
+
+	if (i == -1)
+		err(EX_UNAVAILABLE, "Error performing SMBus IO");
+	else if (i == -2)
+		errx(EX_USAGE, "Invalid option combination");
+
+	return 0;
+}