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 pointer to Vt 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 Fa 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 Ta Description

SMB_QUICK_WRITE Ta The

QuickWrite command just issues the device address with write intent to the bus, without transferring any data.

SMB_QUICK_READ Ta The

QuickRead command just issues the device address with read intent to the bus, without transferring any data.

SMB_SENDB Ta The

SendByte command sends the byte provided in the Fa cmd field to the device.

SMB_RECVB Ta The

ReceiveByte command reads a single byte from the device which will be returned in the Fa cmd field.

SMB_WRITEB Ta The

WriteByte command first sends the byte from the Fa cmd field to the device, followed by the byte given in Fa data.byte .

SMB_WRITEW Ta The

WriteWord command first sends the byte from the Fa cmd field to the device, followed by the word given in Fa data.word . Note that the SMBus byte-order is little-endian by definition.

SMB_READB Ta The

ReadByte command first sends the byte from the Fa 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 Fa data.byte_ptr .

SMB_READW Ta The

ReadWord command first sends the byte from the Fa 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 Fa data.word_ptr .

SMB_PCALL Ta The

ProcedureCall command first sends the byte from the Fa cmd field to the device, followed by the word provided in Fa data.process.sdata . It then reads one word of data from the device, and returns it in the location pointed to by Fa data.process.rdata .

SMB_BWRITE Ta The

BlockWrite command first sends the byte from the Fa cmd field to the device, followed by Fa count bytes of data that are taken from the buffer pointed to by Fa 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 Ta The

BlockRead command first sends the byte from the Fa cmd field to the device, and then reads Fa count bytes of data that from the device. These data will be returned in the buffer pointed to by Fa data.byte_ptr .

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

HISTORY

The manual page first appeared in Fx 3.0 .

AUTHORS

This manual page was written by An Nicolas Souchu .