.\" Copyright 2017 IBM Corp.
.\" s390-tools is free software; you can redistribute it and/or modify
.\" it under the terms of the MIT license. See LICENSE for details.
.\"
.TH CHCHP 8 "Mar 2007" s390\-tools

.SH NAME
chchp \- modify channel\-path state.

.SH SYNOPSIS
.B chchp
.RB [ \-v|\-\-vary
.IR value ]
.RB [ \-c|\-\-configure
.IR value ]
.RS 6
.br
.RB [ \-a|\-\-attribute
.IR key = value ]
.I chpid
.br
.RB [ \-h|\-\-help ]
.RB [ \-\-version ]

.SH DESCRIPTION
The chchp command modifies the state of one or more channel\-paths.
Channel\-path identifiers are specified in hexadecimal notation either simply
as the CHPID\-number (e.g. e0) or in the form

.RS
<cssid>.<id>
.RE

where <cssid> is the channel\-subsystem identifier and <id> is the CHPID\-number (e.g. 0.7e).

An operation can be performed on more than one channel\-path by specifying
multiple identifiers as a blank or comma\-separated list or a range or a
combination of both (see EXAMPLES section).

Note that modifying the state of channel\-paths can affect the availability
of I/O devices as well as trigger associated functions (e.g. channel\-path
verification or device scanning) which in turn can result in a temporary
increase in processor, memory and I/O load.
.SH OPTIONS
.BI "\-v " value
.br
.BI "\-\-vary " value
.RS
Change the logical channel\-path state to
.IR value .
The logical channel\-path state determines whether Linux will be actively
using a channel\-path for I/O.
.br

.RI "A " value
of "0" specifies the logical offline state. A value of "1" specifies the logical
online state.
.br

Note that setting the logical state to offline may cause a currently running
I/O operation to be aborted.
.RE

.BI "\-c " value
.br
.BI "\-\-configure " value
.RS
Change the channel\-path configuration state to
.IR value .
.br

.RI "A " value
of "0" specifies standby state. A value of "1" specifies configured state.
.br

Note that setting the configured state to standby may cause a currently running
I/O operation to be aborted.
.RE

.B "\-a "
.IR key = value
.br
.B \-\-attribute
.IR key = value
.RS
Change the channel\-path sysfs attribute
.IR key " to " value .
.br

.I key
can be the name of any available channel-path sysfs attribute (e.g. "configure"
or "status"), while
.I value
can take any valid value that may be written to the attribute (e.g. "0"
or "offline").
.br

This is a more generic way of modifying the state of a channel-path via
the sysfs interface. It is intended for cases where sysfs attributes
or attribute values are available in the kernel but not in chchp.
.RE


.B \-h
.br
.B \-\-help
.RS
Print a short help text, then exit.
.RE

.B \-V
.br
.B \-\-version
.RS
Print version number, then exit.
.RE

.SH EXAMPLES

.B chchp \-c 0 19
.RS
Put channel\-path 0.19 into standby state.
.RE

.B chchp \-a configure=0 19
.RS
Write value "0" into sysfs attribute "configure" of channel-path 0.19. The
result is the same as when using the command chchp \-c 0 19
.RE

.B chchp \-c 1 0.65\-0.6f
.RS
Put channel\-paths 0.65 to 0.6f into configured state.
.RE

.B chchp \-v 0 0.12,0.7f,0.17\-0.20
.RS
Put channel\-paths 0.12, 0.7f and 0.17 to 0.20 into logical offline state.
.RE

.SH SEE ALSO
.BR lschp (8)