Now that I learned about how all this is working together, quickly
document it for anyone else who might be interested in it. MFC after: 2 weeks
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Joerg Wunsch
parent
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commit
7d2d5f8049
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=129356
@ -1,4 +1,5 @@
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.\" Copyright (c) 1998, Nicolas Souchu
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.\" Copyright (c) 2004, Joerg Wunsch
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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@ -38,26 +39,157 @@ The
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character device driver provides generic i/o to any
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.Xr smbus 4
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instance.
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In order to control SMB devices, use /dev/smb? with the
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following ioctls:
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In order to control SMB devices, use
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.Pa /dev/smb Ns Em ?
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with the ioctls described below.
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Any of these ioctl commands takes a pointer to
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.Vt struct smbcmd
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as its argument.
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.Pp
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.Bl -column "System Management Bus ioctls" -compact
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.Bd -literal
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#include <sys/types.h>
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struct smbcmd {
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char cmd;
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int count;
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u_char slave;
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union {
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char byte;
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short word;
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char *byte_ptr;
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short *word_ptr;
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struct {
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short sdata;
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short *rdata;
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} process;
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} data;
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};
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.Ed
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.Pp
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The
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.Fa slave
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field is always used, and provides the address of the
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SMBus slave device to talk to.
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.Pp
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.Bl -column ".Sy SMB_QUICK_WRITE" -compact
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.It Em Ioctl Ta Em Description
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.It Sy SMB_QUICK_WRITE Ta "QuickWrite command"
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.It Sy SMB_QUICK_READ Ta "QuickRead command"
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.It Sy SMB_SENDB Ta "SendByte command"
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.It Sy SMB_RECVB Ta "ReceiveByte command"
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.It Sy SMB_WRITEB Ta "WriteByte command"
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.It Sy SMB_WRITEW Ta "WriteWord command"
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.It Sy SMB_READB Ta "ReadByte command"
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.It Sy SMB_READW Ta "ReadWord command"
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.It Sy SMB_PCALL Ta "ProcedureCall command"
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.It Sy SMB_BWRITE Ta "BlockWrite command"
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.It Sy SMB_BREAD Ta "BlockRead command"
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.Pp
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.It Sy SMB_QUICK_WRITE Ta
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The
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.Em QuickWrite
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command just issues the device address with write intent
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to the bus, without transferring any data.
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.It Sy SMB_QUICK_READ Ta
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The
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.Em QuickRead
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command just issues the device address with read intent
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to the bus, without transferring any data.
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.It Sy SMB_SENDB Ta
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The
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.Em SendByte
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command sends the byte provided in the
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.Fa cmd
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field to the device.
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.It Sy SMB_RECVB Ta
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The
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.Em ReceiveByte
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command reads a single byte from the device which will
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be returned in the
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.Fa cmd
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field.
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.It Sy SMB_WRITEB Ta
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The
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.Em WriteByte
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command first sends the byte from the
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.Fa cmd
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field to the device, followed by the byte given in
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.Fa data.byte .
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.It Sy SMB_WRITEW Ta
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The
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.Em WriteWord
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command first sends the byte from the
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.Fa cmd
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field to the device, followed by the word given in
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.Fa data.word .
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Note that the SMBus byte-order is little-endian by definition.
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.It Sy SMB_READB Ta
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The
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.Em ReadByte
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command first sends the byte from the
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.Fa cmd
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field to the device, and then reads one byte of data from
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the device.
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The returned data will be stored in the location pointed to by
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.Fa data.byte_ptr .
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.It Sy SMB_READW Ta
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The
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.Em ReadWord
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command first sends the byte from the
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.Fa cmd
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field to the device, and then reads one word of data from
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the device.
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The returned data will be stored in the location pointed to by
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.Fa data.word_ptr .
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.It Sy SMB_PCALL Ta
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The
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.Em ProcedureCall
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command first sends the byte from the
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.Fa cmd
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field to the device, followed by the word provided in
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.Fa data.process.sdata .
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It then reads one word of data from the device, and returns it
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in the location pointed to by
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.Fa data.process.rdata .
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.It Sy SMB_BWRITE Ta
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The
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.Em BlockWrite
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command first sends the byte from the
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.Fa cmd
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field to the device, followed by
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.Fa count
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bytes of data that are taken from the buffer pointed to by
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.Fa data.byte_ptr .
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The SMBus specification mandates that no more than 32 bytes of
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data can be transferred in a single block read or write command.
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This value is available in the constant
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.Dv SMB_MAXBLOCKSIZE .
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.It Sy SMB_BREAD Ta
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The
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.Em BlockRead
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command first sends the byte from the
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.Fa cmd
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field to the device, and then reads
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.Fa count
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bytes of data that from the device.
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These data will be returned in the buffer pointed to by
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.Fa data.byte_ptr .
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.El
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.Pp
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Using the write routine is equivalent to a SMB_WRITEW ioctl.
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The
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.Xr read 2
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and
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.Xr write 2
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system calls are not implemented by this driver.
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.Sh ERRORS
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The
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.Xr ioctl
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commands can cause the following driver-specific errors:
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.Bl -tag -width Er
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.It Bq Er ENXIO
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Device did not respond to selection.
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.It Bq Er EBUSY
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Device still in use.
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.It Bq Er ENODEV
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Operation not supported by device (not supposed to happen).
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.It Bq Er EINVAL
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General argument error.
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.It Bq Er EWOULDBLOCK
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SMBus transaction timed out.
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.El
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.Sh SEE ALSO
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.Xr ioctl 2 ,
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.Xr smbus 4
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.Sh HISTORY
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The
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