smb(4)

NAME

smb - SMB generic I/O device driver

SYNOPSIS

device smb

DESCRIPTION

The smb character device driver provides generic i/o to any

smbus(4)
instance. In order to control SMB devices, use /dev/smb?

with the ioctls
described below. Any of these ioctl commands takes a point

er to struct
smbcmd as its argument.

#include <sys/types.h>

struct smbcmd {

char cmd;
int count;
u_char slave;
union {

char byte;
short word;

char *byte_ptr;
short *word_ptr;

struct {

short sdata;
short *rdata;

} process;

} data;

};

The slave field is always used, and provides the address of

the SMBus
slave device to talk to.

Ioctl Description

SMB_QUICK_WRITE The QuickWrite command just issues

the device

address with write intent to the bus,

without
transferring any data.

SMB_QUICK_READ The QuickRead command just issues the

device

address with read intent to the bus,

without
transferring any data.

SMB_SENDB The SendByte command sends the byte

provided in

the cmd field to the device.

SMB_RECVB The ReceiveByte command reads a sin

gle byte from

the device which will be returned in

the cmd
field.

SMB_WRITEB The WriteByte command first sends the

byte from

the cmd field to the device, followed

by the byte
given in data.byte.

SMB_WRITEW The WriteWord command first sends the

byte from

the cmd field to the device, followed

by the word
given in data.word. Note that the

SMBus byteorder is little-endian by definition.

SMB_READB The ReadByte command first sends the

byte from the

cmd field to the device, and then

reads one byte
of data from the device. The re

turned data will
be stored in the location pointed to

by
data.byte_ptr.

SMB_READW The ReadWord command first sends the

byte from the

cmd field to the device, and then

reads one word
of data from the device. The re

turned data will
be stored in the location pointed to

by
data.word_ptr.

SMB_PCALL The ProcedureCall command first sends

the byte

from the cmd field to the device,

followed by the
word provided in data.process.sdata.

It then
reads one word of data from the de

vice, and
returns it in the location pointed to

by
data.process.rdata.

SMB_BWRITE The BlockWrite command first sends

the byte from

the cmd field to the device, followed

by count
bytes of data that are taken from the

buffer
pointed to by data.byte_ptr. The SM

Bus specification mandates that no more than 32

bytes of data
can be transferred in a single block

read or write
command. This value is available in

the constant
SMB_MAXBLOCKSIZE.

SMB_BREAD The BlockRead command first sends the

byte from

the cmd field to the device, and then

reads count
bytes of data that from the device.

These data
will be returned in the buffer point

ed to by
data.byte_ptr.

The read(2) and write(2) system calls are not implemented by

this driver.

ERRORS

The ioctl(2) commands can cause the following driver-specif

ic errors:

[ENXIO] Device did not respond to selection.

[EBUSY] Device still in use.

[ENODEV] Operation not supported by device (not

supposed to

happen).

[EINVAL] General argument error.

[EWOULDBLOCK] SMBus transaction timed out.

SEE ALSO

ioctl(2), smbus(4)

HISTORY

The smb manual page first appeared in FreeBSD 3.0.

AUTHORS

This manual page was written by Nicolas Souchu.

BSD October 25, 1998

BSD