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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.  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.