smb —
SMB
generic I/O device driver
device smb
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. Note that
the SMBus byte-order is little-endian by definition. |
SMB_READB |
ReadByte first sends the
byte from cmd to the device, then reads
one byte of data from the device. Returned data is stored in
rdata.byte. |
SMB_READW |
ReadWord first sends the
byte from cmd to the device, then reads
one word of data from the 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.
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.
ioctl(2),
smbus(4)
The
smb manual page first appeared in
FreeBSD 3.0.
This manual page was written by
Nicolas
Souchu and extended by
Michael Gmelin
⟨
[email protected]⟩.