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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.

     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.