freebsd-nq/share/man/man4/smb.4

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.Dd February 6, 2009
.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
.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 <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;
};
.Ed
.Pp
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
.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
The
.Em QuickWrite
command just issues the device address with write intent
to the bus, without transferring any data.
.It Dv SMB_QUICK_READ Ta
The
.Em QuickRead
command just issues the device address with read intent
to the bus, without transferring any data.
.It Dv SMB_SENDB Ta
The
.Em SendByte
command sends the byte provided in the
.Fa cmd
field to the device.
.It Dv SMB_RECVB Ta
The
.Em ReceiveByte
command reads a single byte from the device which will
be returned in the
.Fa cmd
field.
.It 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 data.byte .
.It 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 data.word .
Note that the SMBus byte-order is little-endian by definition.
.It 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 the location pointed to by
.Fa data.byte_ptr .
.It 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 the location pointed to by
.Fa data.word_ptr .
.It 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 data.process.sdata .
It then reads one word of data from the device, and returns it
in the location pointed to by
.Fa data.process.rdata .
.It Dv SMB_BWRITE Ta
The
.Em BlockWrite
command first sends the byte from the
.Fa cmd
field to the device, followed by
.Fa count
bytes of data that are taken from the buffer pointed to by
.Fa 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
.Dv SMB_MAXBLOCKSIZE .
.It Dv SMB_BREAD Ta
The
.Em BlockRead
command first sends the byte from the
.Fa cmd
field to the device, and then reads
.Fa count
bytes of data that from the device.
These data will be returned in the buffer pointed to by
.Fa data.byte_ptr .
.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 .