Copyright (c) 2004, Joerg Wunsch
Copyright (c) 2015, Michael Gmelin <freebsd@grem.de>
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$FreeBSD: head/share/man/man4/smb.4 281985 2015-04-25 16:15:01Z grembo $
.Dd April 25, 2015 .Dt SMB 4 .Os .Sh NAME .Nm smb .Nd SMB 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. In order to control SMB devices, use
a /dev/smb? with the ioctls described below. Any of these ioctl commands takes a pointer to .Vt struct smbcmd as its argument. d -literal #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; }; .Ed
p The .Fa 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
q i.e. Dq "left-justified" . The least significant bit of the slave address must be zero.
p l -column ".Dv SMB_QUICK_WRITE" -compact t Em Ioctl Ta Em Description
p t Dv SMB_QUICK_WRITE Ta The .Em QuickWrite command just issues the device address with write intent to the bus, without transferring any data. t Dv SMB_QUICK_READ Ta The .Em QuickRead command just issues the device address with read intent to the bus, without transferring any data. t Dv SMB_SENDB Ta The .Em SendByte command sends the byte provided in the .Fa cmd field to the device. t Dv SMB_RECVB Ta The .Em ReceiveByte command reads a single byte from the device which will be returned in the .Fa cmd field. t Dv SMB_WRITEB Ta The .Em WriteByte command first sends the byte from the .Fa cmd field to the device, followed by the byte given in .Fa wdata.byte . t Dv SMB_WRITEW Ta The .Em WriteWord command first sends the byte from the .Fa cmd field to the device, followed by the word given in .Fa wdata.word . Note that the SMBus byte-order is little-endian by definition. t Dv SMB_READB Ta The .Em ReadByte command first sends the byte from the .Fa cmd field to the device, and then reads one byte of data from the device. The returned data will be stored in .Fa rdata.byte . t Dv SMB_READW Ta The .Em ReadWord command first sends the byte from the .Fa cmd field to the device, and then reads one word of data from the device. The returned data will be stored in .Fa rdata.word . t Dv SMB_PCALL Ta The .Em ProcedureCall command first sends the byte from the .Fa cmd field 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 . t Dv SMB_BWRITE Ta The .Em BlockWrite command first sends the byte from the .Fa cmd field to the device, 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, but since .Xr smbus 4 is also used to access I2C devices, the limit has been increased to 1024. This value is available in the constant .Dv SMB_MAXBLOCKSIZE . t Dv SMB_BREAD Ta The .Em BlockRead command first sends the byte from the .Fa cmd field to the device, and then reads .Fa rcount bytes of data that from the device. These data will be returned in the buffer pointed to by .Fa rbuf . t Dv SMB_TRANS Ta The .Em Trans command sends an SMB roll-up transaction with flags that also allow it to be used for (mostly) I2C pass-through and with with 10-bit addresses. This function can be used to roll up all of the above functions. It first sends the byte from the .Fa cmd field to the device, followed by .Fa wcount bytes of data that are taken from the buffer pointed to by .Fa wbuf , then reads .Fa rcount bytes of data that from the device. These data will be returned in the buffer pointed to by .Fa rbuf .
p The following flags are allowed in .Fa op :
p d -literal -compact SMB_TRANS_NOSTOP Do not send STOP at end SMB_TRANS_NOCMD Ignore cmd field (do not tx) SMB_TRANS_NOCNT Do not tx or rx count field SMB_TRANS_7BIT Change address mode to 7-bit SMB_TRANS_10BIT Change address mode to 10-bit .Ed .El
p 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: l -tag -width Er t Bq Er ENXIO Device did not respond to selection. t Bq Er EBUSY Device still in use. t Bq Er ENODEV Operation not supported by device (not supposed to happen). t Bq Er EINVAL General argument error. t 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 .