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.  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 provided in data.process.sdata.  It then
                        reads one word of data from the device, and returns it in the location
                        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 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.