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.
                            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.

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 13.1-RELEASE-p6         April 25, 2015         FreeBSD 13.1-RELEASE-p6