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SMBMSG(8)		  BSD System Manager's Manual		     SMBMSG(8)

     smbmsg -- send or receive messages	over an	SMBus

     smbmsg [-f	dev] -p

     smbmsg [-f	dev] -s	slave [-F fmt] [-c cmd]	[-w] [-i incnt]	[-o outcnt]
	    [outdata ...]

     The smbmsg	utility	can be used to send or receive messages	over an	SMBus,
     see smbus(4).

     The smbmsg	utility	has two	different modi of operation.  The first	form
     shown in the synopsis can be used to "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 re-
     quests will by displayed by their device address, followed	by the strings
     `r', `w', or `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 -p option	that choses the	modus)
     is	-f dev.	 See below for a description.

     Note that probing the bus is risky, since individual devices could	per-
     form unwanted actions upon	receiving one of the mentioned messages.  For
     example, if a particular SMBus device considers any write operation is-
     sued to it	as a request to	power off the system, the probing would	trig-
     ger this action.

     The second	form shown in the synopsis can be used to send or receive ar-
     bitrary 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.

     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 `C' notation (prefix 0 for	octal inter-
     pretation,	or 0x for hexadecimal interpretation).

     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.

     The options are as	follows:

     -F	fmt	Specify	the 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 `0x%02x'
		for byte input operations, and to `0x%04x' for word input op-
		erations.  For multi-byte input	(block read), the same format
		is used	for each individual byte read from the SMBus.

     -c	cmd	This is	the value of the command byte to be issued as part of
		the SMBus message.

     -f	dev	This specifies that dev	should be used as the connection to
		the SMBus, rather than the default of /dev/smb0.

     -i	incnt	An SMBus message should	be generated to	read incnt bytes from
		the device.

     -o	outcnt	An SMBus message should	be generated to	write 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 outcnt value.

     -p		This selects the probe bus modus of operation.

     -s	slave	The slave parameter specifies which SMBus device to connect
		to.  This option also selects the transfer messages from/to
		device modus of	operation, where a slave address is mandatory.

     -w		This option specifies that IO operations are word operations,
		rather than byte operations.  Either incnt, or 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).

     Not all argument combinations make	sense in order to form valid SMBus
     messages.	If no -c cmd option has	been provided, the following messages
     can be issued:

	   message	  incnt	  outcnt
	   quick read	      0	       -
	   quick write	      -	       0
	   receive byte	      1	       -
	   send	byte	      -	       1

     Note in particular	that specifying	0 as a count value has a different
     meaning than omitting the respective option entirely.

     If	a command value	has been given using the -c cmd	option,	the following
     messages can be generated:

	   message	  -w	incnt	outcnt
	   read	byte	  no	    1	     -
	   write byte	  no	    -	     1
	   read	word	  yes	    2	     -
	   write word	  yes	    -	     2
	   process call	  yes	    2	     2
	   block read	  no	 >= 2	     -
	   block write	  no	    -	  >= 2

     /dev/smb0	The default device to connect to, unless -f dev	has been pro-

     Typical usage examples of the smbmsg command include:

	   smbmsg -f /dev/smb1 -p

     Probe all devices on the SMBus attached to	/dev/smb1.

	   smbmsg -s 0x70 -i 1

     Issue a receive byte message to the device	at address 0x70, and display
     the received byte using the default format.

	   smbmsg -s 0x70 -c 0xff -i 1 -F %d

     Issue a 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'.

	   smbmsg -s 0xa0 -c 0 -o 1 0x80

     Send a 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.

	   smbmsg -s 0xa0 -c 1 -i 6 -F %02x

     Send a 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.

	   smbmsg -s 0xa0 -c 2 -o 5 0x00 0x07 0x22 0x16	0x05

     Send a 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.

     Exit status is 0 on success, or according to sysexits(3) in case of fail-
     ure.  Diagnostic messages issued are supposed to be self-explanatory.

     printf(3),	sysexits(3), smb(4), smbus(4)

     The SMBus specification,

     The smbmsg	utility	first appeared in FreeBSD 5.3.

     The smbmsg	utility	and this manual	page were written by Jorg Wunsch.

BSD				 May 16, 2004				   BSD


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