doc/sg_reset.8 - platform/external/sg3_utils - Git at Google

 .TH SG_RESET "8" "July 2009" "sg3_utils\-1.28" SG3_UTILS
 .SH NAME
 sg_reset \- sends SCSI device, target, bus or host reset; or checks reset state
 .SH SYNOPSIS
 .B sg_reset
 [\fI\-b\fR] [\fI\-d\fR] [\fI\-h\fR] [\fI\-t\fR] [\fI\-V\fR]
 \fIDEVICE\fR
 .SH DESCRIPTION
 .\" Add any additional description here
 .PP
 The sg_reset utility with no options (just a \fIDEVICE\fR) reports on
 the reset state (e.g. if a reset is underway) of \fIDEVICE\fR. When given
 a \fI\-d\fR, \fI\-t\fR, \fI\-b\fR or \fI\-h\fR option it requests a device,
 target, bus or host reset respectively.
 .PP
 The ability to reset a SCSI target (often called a "hard reset" at the
 transport level) was added in linux kernel 2.6.27 . Low level drivers that
 support target reset hopefully reset a logical unit only when given the
 device reset (i.e. \fI\-d\fR) option. This should removed the ambiguity of
 whether "device" meant LU or target that we have had in the past.
 .PP
 In the linux kernel 2.6 series this utility can be called on sd,
 sr (cd/dvd), st or sg device nodes; if the user has appropriate
 permissions.
 .PP
 In the linux kernel 2.4 series support for this utility first
 appeared in lk 2.4.19 and could only be called on sg device
 nodes. Various vendors made this capability available in their
 kernels prior to lk 2.4.19.
 .SH OPTIONS
 .TP
 \fB\-b\fR
 attempt a SCSI bus reset. This would normally be tried if the
 device reset (i.e. option \fI\-d\fR) was not successful.
 .TP
 \fB\-d\fR
 attempt a SCSI device reset. If the device seems stuck, this is
 the first reset that should be tried. This assumes the linux
 scsi mid level error handler is not already in the process
 of resetting \fIDEVICE\fR.
 .TP
 \fB\-h\fR
 attempt a host adapter reset. This would normally be tried if both
 device reset (i.e. option \fI\-d\fR) and bus reset (i.e. option \fI\-b\fR)
 were not successful.
 .TP
 \fB\-t\fR
 attempt a SCSI target reset. This assumes the linux scsi mid level
 error handler is not already in the process of resetting the target that
 contains the given \fIDEVICE\fR.
 .TP
 \fB\-V\fR
 prints the version string then exits.
 .SH NOTES
 The error recovery code within the linux kernel when faced with a SCSI command
 timing out and no response from the device (LU), first tries a device reset
 and if that is not successful tries a target reset. If that is not successful
 it tries a bus reset. If that is not successful it tries a host reset. Users
 of this utility should check whether such a recovery is already underway
 before trying to reset with this utility. The "device,target,bus,host"
 order is also recommended (i.e. first start with the smallest
 hammer). The above is a generalization and exact details will vary depending
 on the transport and the low level driver concerned.
 .PP
 SAM\-4 defines a hard reset, a logical unit reset and a I_T nexus reset. A
 hard reset is defined to be a power on condition, a microcode change or a
 transport reset event. A LU reset and an I_T nexus reset can be requested
 via task management function (and support for LU reset is mandatory). In
 Linux the SCSI subsystem leaves it up to the low level drivers as to whether
 a "device reset" is only for the addressed LU or all the LUs in the device
 that contains the addressed LU (i.e. a target reset). The additional of the
 target reset (i.e. option \fI\-t\fR) should give more control in this area.
 The "bus reset" is a transport reset and may be a dummy operation, depending
 on the transport. A "host reset" attempts to re\-initialize the HBA that the
 request passes through en route to the \fIDEVICE\fR. Note that a "host reset"
 and a "bus reset" may cause collateral damage.
 .PP
 This utility does not allow individual SCSI commands (or tasks as they are
 called in SAM\-4) to be aborted. SAM\-4 defines ABORT TASK and ABORT TASK
 SET task management functions for that.
 .PP
 Prior to SAM\-3 there was a TARGET RESET task management function. Several
 transports still support that function and many associated linux low level
 drivers map the \fI\-t\fR option to it.
 .SH AUTHORS
 Written by Douglas Gilbert.
 .SH COPYRIGHT
 Copyright \(co 1999\-2009 Douglas Gilbert
 .br
 This software is distributed under the GPL version 2. There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	.TH SG_RESET "8" "July 2009" "sg3_utils\-1.28" SG3_UTILS
	.SH NAME
	sg_reset \- sends SCSI device, target, bus or host reset; or checks reset state
	.SH SYNOPSIS
	.B sg_reset
	[\fI\-b\fR] [\fI\-d\fR] [\fI\-h\fR] [\fI\-t\fR] [\fI\-V\fR]
	\fIDEVICE\fR
	.SH DESCRIPTION
	.\" Add any additional description here
	.PP
	The sg_reset utility with no options (just a \fIDEVICE\fR) reports on
	the reset state (e.g. if a reset is underway) of \fIDEVICE\fR. When given
	a \fI\-d\fR, \fI\-t\fR, \fI\-b\fR or \fI\-h\fR option it requests a device,
	target, bus or host reset respectively.
	.PP
	The ability to reset a SCSI target (often called a "hard reset" at the
	transport level) was added in linux kernel 2.6.27 . Low level drivers that
	support target reset hopefully reset a logical unit only when given the
	device reset (i.e. \fI\-d\fR) option. This should removed the ambiguity of
	whether "device" meant LU or target that we have had in the past.
	.PP
	In the linux kernel 2.6 series this utility can be called on sd,
	sr (cd/dvd), st or sg device nodes; if the user has appropriate
	permissions.
	.PP
	In the linux kernel 2.4 series support for this utility first
	appeared in lk 2.4.19 and could only be called on sg device
	nodes. Various vendors made this capability available in their
	kernels prior to lk 2.4.19.
	.SH OPTIONS
	.TP
	\fB\-b\fR
	attempt a SCSI bus reset. This would normally be tried if the
	device reset (i.e. option \fI\-d\fR) was not successful.
	.TP
	\fB\-d\fR
	attempt a SCSI device reset. If the device seems stuck, this is
	the first reset that should be tried. This assumes the linux
	scsi mid level error handler is not already in the process
	of resetting \fIDEVICE\fR.
	.TP
	\fB\-h\fR
	attempt a host adapter reset. This would normally be tried if both
	device reset (i.e. option \fI\-d\fR) and bus reset (i.e. option \fI\-b\fR)
	were not successful.
	.TP
	\fB\-t\fR
	attempt a SCSI target reset. This assumes the linux scsi mid level
	error handler is not already in the process of resetting the target that
	contains the given \fIDEVICE\fR.
	.TP
	\fB\-V\fR
	prints the version string then exits.
	.SH NOTES
	The error recovery code within the linux kernel when faced with a SCSI command
	timing out and no response from the device (LU), first tries a device reset
	and if that is not successful tries a target reset. If that is not successful
	it tries a bus reset. If that is not successful it tries a host reset. Users
	of this utility should check whether such a recovery is already underway
	before trying to reset with this utility. The "device,target,bus,host"
	order is also recommended (i.e. first start with the smallest
	hammer). The above is a generalization and exact details will vary depending
	on the transport and the low level driver concerned.
	.PP
	SAM\-4 defines a hard reset, a logical unit reset and a I_T nexus reset. A
	hard reset is defined to be a power on condition, a microcode change or a
	transport reset event. A LU reset and an I_T nexus reset can be requested
	via task management function (and support for LU reset is mandatory). In
	Linux the SCSI subsystem leaves it up to the low level drivers as to whether
	a "device reset" is only for the addressed LU or all the LUs in the device
	that contains the addressed LU (i.e. a target reset). The additional of the
	target reset (i.e. option \fI\-t\fR) should give more control in this area.
	The "bus reset" is a transport reset and may be a dummy operation, depending
	on the transport. A "host reset" attempts to re\-initialize the HBA that the
	request passes through en route to the \fIDEVICE\fR. Note that a "host reset"
	and a "bus reset" may cause collateral damage.
	.PP
	This utility does not allow individual SCSI commands (or tasks as they are
	called in SAM\-4) to be aborted. SAM\-4 defines ABORT TASK and ABORT TASK
	SET task management functions for that.
	.PP
	Prior to SAM\-3 there was a TARGET RESET task management function. Several
	transports still support that function and many associated linux low level
	drivers map the \fI\-t\fR option to it.
	.SH AUTHORS
	Written by Douglas Gilbert.
	.SH COPYRIGHT
	Copyright \(co 1999\-2009 Douglas Gilbert
	.br
	This software is distributed under the GPL version 2. There is NO
	warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.