xref: /freebsd/share/man/man9/device_probe_and_attach.9 (revision d7fa71dfedd6db18ded3971c6f42b3699b5627d7)

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.Dd February 5, 2025
.Dt DEVICE_PROBE_AND_ATTACH 9
.Os
.Sh NAME
.Nm device_attach ,
.Nm device_detach ,
.Nm device_probe ,
.Nm device_probe_and_attach
.Nd manage device's connection to a device driver
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Ft int
.Fn device_attach "device_t dev"
.Ft int
.Fn device_detach "device_t dev"
.Ft int
.Fn device_probe "device_t dev"
.Ft int
.Fn device_probe_and_attach "device_t dev"
.Sh DESCRIPTION
These functions manage the relationship between a device and device drivers.
.Pp
.Fn device_probe
invokes the
.Xr DEVICE_PROBE 9
method of each suitable driver and to find the driver with the best match for
.Fa dev .
If a matching driver is found,
.Fa dev
is set to the
.Dv DS_ALIVE
state and zero is returned.
If
.Fa dev
is already attached to a device driver or has been disabled via
.Xr device_disable 9 ,
then it will not be probed and -1 is returned.
.Pp
.Fn device_attach
fully attaches a device driver to
.Fa dev .
This function prints a description of the device and invokes the
.Xr DEVICE_ATTACH 9
method.
If the
.Xr DEVICE_ATTACH 9
method succeeds,
.Fa dev
is set to the
.Dv DS_ATTACHED
state and zero is returned.
If the
.Xr DEVICE_ATTACH 9
method fails,
.Xr BUS_CHILD_DETACHED 9
is called and an error value is returned.
.Pp
If the device name and unit are disabled by a hint,
.Fn device_attach
disables the device, demotes it to the
.Dv DS_NOTPRESENT
state,
and returns
.Dv ENXIO .
The device retains its device name and unit and can be re-enabled via
.Xr devctl 8 .
.Pp
.Fn device_probe_and_attach
is a wrapper function around
.Fn device_probe
and
.Fn device_attach
that fully initialises a device.
If
.Fa dev
is already attached or disabled,
.Fn device_probe_and_attach
leaves the device unchanged and returns zero.
Otherwise,
.Fn device_probe
is used to identify a device driver for
.Fa dev
and
.Fn device_attach
finalizes attaching the driver to
.Fa dev .
Device drivers should generally use this function to initialize a device
rather than direct calls to
.Fn device_probe
and
.Fn device_attach .
.Pp
.Fn device_detach
detaches the device driver from
.Fa dev .
This function invokes the
.Xr DEVICE_DETACH 9
method to tear down device driver state for
.Fa dev .
If the method fails,
its error value is returned and
.Fa dev
remains attached.
If the method succeeds,
otherwise,
.Xr BUS_CHILD_DETACHED 9
is called,
the device is set to the
.Dv DS_NOTPRESENT
state,
and zero is returned.
If a device is busy,
.Fn device_detach
fails with
.Dv EBUSY
and leaving
.Fa dev
unchanged.
.Sh RETURN VALUES
Zero is returned on success, otherwise an appropriate error is returned.
In addition,
.Fn device_probe
returns -1 if
.Fa dev
is disabled or already attached.
.Sh SEE ALSO
.Xr devctl 8 ,
.Xr BUS_CHILD_DETACHED 9 ,
.Xr device 9 ,
.Xr DEVICE_ATTACH 9 ,
.Xr DEVICE_DETACH 9 ,
.Xr DEVICE_PROBE 9 ,
.Xr driver 9
.Sh AUTHORS
This manual page was written by
.An Doug Rabson .