SMB(4) BSD Kernel Interfaces Manual SMB(4)NAMEsmb — SMB generic I/O device driver
SYNOPSIS
device smbDESCRIPTION
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 pointer 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. The slave address is specified in the seven
most significant bits (i.e. “left-justified”). The least significant bit
of the slave address must be zero.
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 single 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 byte-order 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 returned 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 returned 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 pro‐
vided in data.process.sdata. It then reads one word
of data from the device, and returns it in the loca‐
tion 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 SMBus 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 pointed 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-specific 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 ALSOioctl(2), smbus(4)HISTORY
The smb manual page first appeared in FreeBSD 3.0.
AUTHORS
This manual page was written by Nicolas Souchu.
BSD February 6, 2009 BSD
