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freebsd-dev/lib/libdevctl/devctl.3
Warner Losh b01f409ffe libdevctl: Add devctl_getpath 
Helper routine to call the kernel to get a path to the named device.
Different path enumeration methods (called locators) can be used
for different path types depending on what the kernel implements.

Sponsored by:		Netflix
Reviewed by:		jhb
Differential Revision:	https://reviews.freebsd.org/D32746
2022-03-01 08:06:41 -07:00

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.\"
.\" Copyright (c) 2014 John Baldwin <jhb@FreeBSD.org>
.\"
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.\" modification, are permitted provided that the following conditions
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.\" $FreeBSD$
.\"
.Dd April 4, 2019
.Dt DEVCTL 3
.Os
.Sh NAME
.Nm devctl ,
.Nm devctl_attach ,
.Nm devctl_clear_driver ,
.Nm devctl_delete ,
.Nm devctl_detach ,
.Nm devctl_disable ,
.Nm devctl_enable ,
.Nm devctl_freeze ,
.Nm devctl_getpath ,
.Nm devctl_rescan ,
.Nm devctl_reset ,
.Nm devctl_resume ,
.Nm devctl_set_driver ,
.Nm devctl_suspend ,
.Nm devctl_thaw
.Nd device control library
.Sh LIBRARY
.Lb libdevctl
.Sh SYNOPSIS
.In devctl.h
.Ft int
.Fn devctl_attach "const char *device"
.Ft int
.Fn devctl_clear_driver "const char *device" "bool force"
.Ft int
.Fn devctl_delete "const char *device" "bool force"
.Ft int
.Fn devctl_detach "const char *device" "bool force"
.Ft int
.Fn devctl_disable "const char *device" "bool force_detach"
.Ft int
.Fn devctl_enable "const char *device"
.Ft int
.Fn devctl_freeze "void"
.Ft int
.Fn devctl_getpath "const char *device" "const char *locator" "char **buffer"
.Ft int
.Fn devctl_rescan "const char *device"
.Ft int
.Fn devctl_reset "const char *device" "bool detach"
.Ft int
.Fn devctl_resume "const char *device"
.Ft int
.Fn devctl_set_driver "const char *device" "const char *driver" "bool force"
.Ft int
.Fn devctl_suspend "const char *device"
.Ft int
.Fn devctl_thaw "void"
.Sh DESCRIPTION
The
.Nm
library adjusts the state of devices in the kernel's internal device
hierarchy.
Each control operation accepts a
.Fa device
argument that identifies the device to adjust.
The
.Fa device
may be specified as either the name of an existing device or as a
bus-specific address.
The following bus-specific address formats are currently supported:
.Bl -tag -offset indent
.It Sy pci Ns Fa domain Ns : Ns Fa bus Ns : Ns Fa slot Ns : Ns Fa function
A PCI device with the specified
.Fa domain ,
.Fa bus ,
.Fa slot ,
and
.Fa function .
.It Sy pci Ns Fa bus Ns : Ns Fa slot Ns : Ns Fa function
A PCI device in domain zero with the specified
.Fa bus ,
.Fa slot ,
and
.Fa function .
.It Fa handle
A device with an ACPI handle of
.Fa handle .
The handle must be specified as an absolute path and must begin with a
.Dq \e .
.El
.Pp
The
.Fn devctl_attach
function probes a device and attaches a suitable device driver if one is
found.
.Pp
The
.Fn devctl_detach
function detaches a device from its current device driver.
The device is left detached until either a new driver for its parent
bus is loaded or the device is explicitly probed via
.Fn devctl_attach .
If
.Fa force
is true,
the current device driver will be detached even if the device is busy.
.Pp
The
.Fn devctl_delete
function deletes a device from the device tree.
No
If
.Fa force
is true,
the device is deleted even if the device is physically present.
.Pp
The
.Fn devctl_disable
function disables a device.
If the device is currently attached to a device driver,
the device driver will be detached from the device,
but the device will retain its current name.
If
.Fa force_detach
is true,
the current device driver will be detached even if the device is busy.
The device will remain disabled and detached until it is explicitly enabled
via
.Fn devctl_enable .
.Pp
The
.Fn devctl_enable
function re-enables a disabled device.
The device will probe and attach if a suitable device driver is found.
.Pp
The
.Fn devctl_suspend
function suspends a device.
This may include placing the device in a reduced power state,
but any device driver currently attached to the device will remain attached.
.Pp
The
.Fn devctl_resume
function resumes a suspended device to a fully working state.
.Pp
The
.Fn devctl_set_driver
function attaches a device driver named
.Fa driver
to a device.
If the device is already attached and
.Fa force
is false,
the request will fail.
If the device is already attached and
.Fa force
is true,
the device will be detached from its current device driver before it is
attached to the new device driver.
.Pp
The
.Fn devctl_clear_driver
function resets a device so that it can be attached to any valid device
driver rather than only drivers with a previously specified name.
This function is used to undo a previous call to
.Fn devctl_set_driver .
If the device is already attached and
.Fa force
is false,
the request will fail.
If the device is already attached and
.Fa force
is true,
the device will be detached from its current device driver.
After the device's name is reset,
it is reprobed and attached to a suitable device driver if one is found.
.Pp
The
.Fn devctl_rescan
function rescans a bus device checking for devices that have been added or
removed.
.Pp
The
.Fn devctl_getpath
retrieves the path to the
.Fa device
from the kernel using the
.Fa locator
method to construct the path.
The
.Fa buffer
pointer is updated with an allocated buffer that must be freed with
.Xr free .
.Pp
The
.Fn devctl_freeze
function freezes probe and attach processing initiated in response to
drivers being loaded.
.Pp
The
.Fn devctl_thaw
function resumes (thaws the freeze) probe and attach processing
initiated in response to drivers being loaded.
.Pp
The
.Fn devctl_reset
function resets the specified device using bus-specific reset method.
The
.Fa detach
argument, if true, specifies that the device driver is detached before
the reset, and re-attached afterwards.
If false, the device is suspended before the reset, and resumed after.
.Sh RETURN VALUES
.Rv -std devctl_attach devctl_clear_driver devctl_delete devctl_detach \
devctl_disable devctl_enable devctl_suspend devctl_rescan devctl_resume \
devctl_set_driver
.Sh ERRORS
In addition to specific errors noted below,
all of the
.Nm
functions may fail for any of the errors described in
.Xr open 2
as well as:
.Bl -tag -width Er
.It Bq Er EINVAL
The device name is too long.
.It Bq Er ENOENT
No existing device matches the specified name or location.
.It Bq Er EPERM
The current process is not permitted to adjust the state of
.Fa device .
.El
.Pp
The
.Fn devctl_attach
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is already attached.
.It Bq Er ENOMEM
An internal memory allocation request failed.
.It Bq Er ENXIO
The device is disabled.
.It Bq Er ENXIO
No suitable driver for the device could be found,
or the driver failed to attach.
.El
.Pp
The
.Fn devctl_detach
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The current device driver for
.Fa device
is busy and cannot detach at this time.
Note that some drivers may return this even if
.Fa force
is true.
.It Bq Er ENXIO
The device is not attached to a driver.
.It Bq Er ENXIO
The current device driver for
.Fa device
does not support detaching.
.El
.Pp
The
.Fn devctl_enable
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is already enabled.
.It Bq Er ENOMEM
An internal memory allocation request failed.
.It Bq Er ENXIO
No suitable driver for the device could be found,
or the driver failed to attach.
.El
.Pp
The
.Fn devctl_disable
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The current device driver for
.Fa device
is busy and cannot detach at this time.
Note that some drivers may return this even if
.Fa force_detach
is true.
.It Bq Er ENXIO
The device is already disabled.
.It Bq Er ENXIO
The current device driver for
.Fa device
does not support detaching.
.El
.Pp
The
.Fn devctl_suspend
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is already suspended.
.It Bq Er EINVAL
The device to be suspended is the root bus device.
.El
.Pp
The
.Fn devctl_resume
function may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The device is not suspended.
.It Bq Er EINVAL
The device to be resumed is the root bus device.
.El
.Pp
The
.Fn devctl_set_driver
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is currently attached to a device driver and
.Fa force
is false.
.It Bq Er EBUSY
The current device driver for
.Fa device
is busy and cannot detach at this time.
.It Bq Er EFAULT
The
.Fa driver
argument points outside the process' allocated address space.
.It Bq Er ENOENT
No device driver with the requested name exists.
.It Bq Er ENOMEM
An internal memory allocation request failed.
.It Bq Er ENXIO
The device is disabled.
.It Bq Er ENXIO
The new device driver failed to attach.
.El
.Pp
The
.Fn devctl_clear_driver
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is currently attached to a device driver and
.Fa force
is false.
.It Bq Er EBUSY
The current device driver for
.Fa device
is busy and cannot detach at this time.
.It Bq Er EINVAL
The device is not configured for a specific device driver name.
.It Bq Er ENXIO
The device driver chosen after reprobing failed to attach.
.El
.Pp
The
.Fn devctl_rescan
function may fail if:
.Bl -tag -width Er
.It Bq Er ENXIO
The device is not attached to a driver.
.It Bq Er ENXIO
The bus driver does not support rescanning.
.El
.Pp
The
.Fn devctl_delete
function may fail if:
.Bl -tag -width Er
.It Bq Er EBUSY
The device is physically present and
.Fa force
is false.
.It Bq Er EINVAL
.Fa dev
is the root device of the device tree.
.El
.Pp
The
.Fn devctl_reset
function may fail if:
.Bl -tag -width Er
.It Bq Er ENXIO
The bus does not implement the reset method.
.It Bq Er ETIMEDOUT
The device failed to respond after the reset in the time limits
specific to the bus.
.El
The
.Fn devctl_reset
function may also return errors caused by the attach, detach, suspend,
and resume methods of the device driver.
.Sh SEE ALSO
.Xr devinfo 3 ,
.Xr devstat 3 ,
.Xr devctl 8
.Sh HISTORY
The
.Nm
library first appeared in
.Fx 10.3 .
.Sh BUGS
If a device is suspended individually via
.Fn devctl_suspend
and the entire machine is subsequently suspended,
the device will be resumed when the machine resumes.
.Pp
Similarly, if the device is suspended, and
.Fn devctl_reset
is called on the device with
.Fa detach
set to
.Va false ,
the device is resumed by the
.Fn devctl_reset
call.
Or, if the driver for the device is detached manually, and
.Fn devctl_reset
is called on the device with
.Fa detach
set to
.Va true ,
device reset re-attaches the driver.
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