.\" Copyright (c) 1998, Nicolas Souchu .\" Copyright (c) 2004, Joerg Wunsch .\" Copyright (c) 2015, Michael Gmelin .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd April 25, 2015 .Dt SMB 4 .Os .Sh NAME .Nm smb .Nd System Management Bus (SMBus) generic I/O device driver .Sh SYNOPSIS .Cd "device smb" .Sh DESCRIPTION The .Em smb character device driver provides generic I/O to any .Xr smbus 4 instance. To control SMB devices, use .Pa /dev/smb? with the ioctls described below. Any of these ioctl commands takes a pointer to .Vt struct smbcmd as its argument. .Bd -literal #include 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; }; .Ed .Pp The .Fa 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 .Pq i.e., Dq "left-justified" . The least significant bit of the slave address must be zero. .Pp .Bl -column ".Dv SMB_QUICK_WRITE" -compact .It Em Ioctl Ta Em Description .Pp .It Dv SMB_QUICK_WRITE Ta .Em QuickWrite does not transfer any data. It just issues the device address with write intent to the bus. .It Dv SMB_QUICK_READ Ta .Em QuickRead does not transfer any data. It just issues the device address with read intent to the bus. .It Dv SMB_SENDB Ta .Em SendByte sends the byte provided in .Fa cmd to the device. .It Dv SMB_RECVB Ta .Em ReceiveByte reads a single byte from the device which is returned in .Fa cmd . .It Dv SMB_WRITEB Ta .Em WriteByte first sends the byte from .Fa cmd to the device, followed by the byte given in .Fa wdata.byte . .It Dv SMB_WRITEW Ta .Em WriteWord first sends the byte from .Fa cmd to the device, followed by the word given in .Fa wdata.word . Note that the SMBus byte-order is little-endian by definition. .It Dv SMB_READB Ta .Em ReadByte first sends the byte from .Fa cmd to the device, then reads one byte of data from the device. Returned data is stored in .Fa rdata.byte . .It Dv SMB_READW Ta .Em ReadWord first sends the byte from .Fa cmd to the device, then reads one word of data from the device. Returned data is stored in .Fa rdata.word . .It Dv SMB_PCALL Ta .Em ProcedureCall first sends the byte from .Fa cmd to the device, followed by the word provided in .Fa wdata.word . It then reads one word of data from the device and returns it in .Fa rdata.word . .It Dv SMB_BWRITE Ta .Em BlockWrite first sends the byte from .Fa cmd to the device, then the byte from .Fa wcount followed by .Fa wcount bytes of data that are taken from the buffer pointed to by .Fa 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 .Dv SMB_MAXBLOCKSIZE . .It Dv SMB_BREAD Ta .Em BlockRead first sends the byte from .Fa 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 .Fa rcount . The data is returned in the buffer pointed to by .Fa rbuf . .El .Pp The .Xr read 2 and .Xr write 2 system calls are not implemented by this driver. .Sh ERRORS The .Xr ioctl 2 commands can cause the following driver-specific errors: .Bl -tag -width Er .It Bq Er ENXIO Device did not respond to selection. .It Bq Er EBUSY Device still in use. .It Bq Er ENODEV Operation not supported by device (not supposed to happen). .It Bq Er EINVAL General argument error. .It Bq Er EWOULDBLOCK SMBus transaction timed out. .El .Sh SEE ALSO .Xr ioctl 2 , .Xr smbus 4 .Sh HISTORY The .Nm manual page first appeared in .Fx 3.0 . .Sh AUTHORS This manual page was written by .An Nicolas Souchu and extended by .An Michael Gmelin Aq freebsd@grem.de .