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SMB(4) FreeBSD Kernel Interfaces Manual 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. 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 {
u_char cmd;
u_char reserved;
u_short op;
union {
char byte;
char buf[2];
short word;
} wdata;
union {
char byte;
char buf[2];
short word;
} rdata;
int slave;
char *wbuf; /* use wdata if NULL */
int wcount;
char *rbuf; /* use rdata if NULL */
int rcount;
};
The slave field is always used, and provides the address of the SMBus
slave device. 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 QuickWrite does not transfer any data. It just
issues the device address with write intent to the
bus.
SMB_QUICK_READ QuickRead does not transfer any data. It just
issues the device address with read intent to the
bus.
SMB_SENDB SendByte sends the byte provided in cmd to the
device.
SMB_RECVB ReceiveByte reads a single byte from the device
which is returned in cmd.
SMB_WRITEB WriteByte first sends the byte from cmd to the
device, followed by the byte given in wdata.byte.
SMB_WRITEW WriteWord first sends the byte from cmd to the
device, followed by the word given in wdata.word.
device. Returned data is stored in rdata.word.
SMB_PCALL ProcedureCall first sends the byte from cmd to the
device, followed by the word provided in
wdata.word. It then reads one word of data from
the device and returns it in rdata.word.
SMB_BWRITE BlockWrite first sends the byte from cmd to the
device, then the byte from wcount followed by
wcount bytes of data that are taken from the
buffer pointed to by wbuf. 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 can be read from the
constant SMB_MAXBLOCKSIZE.
SMB_BREAD BlockRead first sends the byte from cmd to the
device, then reads a count of data bytes that the
device is going to provide and then reads that
many bytes. The count is returned in rcount. The
data is returned in the buffer pointed to by rbuf.
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 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 and extended by
Michael Gmelin <freebsd@grem.de>.
FreeBSD 14.0-RELEASE-p11 April 25, 2015 FreeBSD 14.0-RELEASE-p11