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it automatically after it runs. The config_intrhook mechanism allows a driver to stall the boot process until device(s) required for booting are available, by not allowing system inits to proceed until all intrhook functions have been unregistered. Virtually all existing code simply unregisters from within the hook function when it gets called. This new function makes that common usage more convenient. Instead of allocating and filling in a struct, passing it to a function that might (in theory) fail, and checking the return code, now a driver can simply call this cannot-fail routine, passing just the intrhook function and its arg. Differential Revision: https://reviews.freebsd.org/D11963
121 lines
4.5 KiB
Groff
121 lines
4.5 KiB
Groff
.\"
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.\" Copyright (C) 2006 M. Warner Losh <imp@FreeBSD.org>. 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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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 10, 2017
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.Dt CONFIG_INTRHOOK 9
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.Os
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.Sh NAME
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.Nm config_intrhook
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.Nd schedule a function to be run after interrupts have been enabled,
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but before root is mounted
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.Sh SYNOPSIS
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.In sys/kernel.h
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.Vt typedef void (*ich_func_t)(void *arg);
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.Ft int
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.Fn config_intrhook_establish "struct intr_config_hook *hook"
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.Ft void
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.Fn config_intrhook_disestablish "struct intr_config_hook *hook"
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.Ft void
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.Fn config_intrhook_oneshot "ich_func_t func" "void *arg"
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.Sh DESCRIPTION
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The
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.Fn config_intrhook_establish
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function schedules a function to be run after interrupts have been
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enabled, but before root is mounted.
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If the system has already passed this point in its initialization,
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the function is called immediately.
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.Pp
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The
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.Fn config_intrhook_disestablish
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function removes the entry from the hook queue.
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.Pp
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The
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.Fn config_intrhook_oneshot
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function schedules a function to be run as described for
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.Fn config_intrhook_establish ;
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the entry is automatically removed from the hook queue
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after that function runs.
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This is appropriate when additional device configuration must be done
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after interrupts are enabled, but there is no need to stall the
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boot process after that.
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This function allocates memory using M_WAITOK; do not call this while
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holding any non-sleepable locks.
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.Pp
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Before root is mounted, all the previously established hooks are
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run.
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The boot process is then stalled until all handlers remove their hook
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from the hook queue with
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.Fn config_intrhook_disestablish .
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The boot process then proceeds to attempt to mount the root file
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system.
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Any driver that can potentially provide devices they wish to be
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mounted as root must use either this hook, or probe all these devices
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in the initial probe.
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Since interrupts are disabled during the probe process, many drivers
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need a method to probe for devices with interrupts enabled.
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.Pp
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The requests are made with the
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.Vt intr_config_hook
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structure.
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This structure is defined as follows:
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.Bd -literal
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struct intr_config_hook {
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TAILQ_ENTRY(intr_config_hook) ich_links;/* Private */
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ich_func_t ich_func; /* function to call */
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void *ich_arg; /* Argument to call */
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};
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.Ed
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.Pp
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Storage for the
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.Vt intr_config_hook
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structure must be provided by the driver.
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It must be stable from just before the hook is established until
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after the hook is disestablished.
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.Pp
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Specifically, hooks are run at
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.Fn SI_SUB_INT_CONFIG_HOOKS ,
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which is immediately after the scheduler is started,
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and just before the root file system device is discovered.
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.Sh RETURN VALUES
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A zero return value means the hook was successfully added to the queue
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(with either deferred or immediate execution).
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A non-zero return value means the hook could not be added to the queue
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because it was already on the queue.
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.Sh SEE ALSO
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.Xr DEVICE_ATTACH 9
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.Sh HISTORY
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These functions were introduced in
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.Fx 3.0
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with the CAM subsystem, but are available for any driver to use.
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.Sh AUTHORS
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.An -nosplit
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The functions were written by
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.An Justin Gibbs Aq Mt gibbs@FreeBSD.org .
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This manual page was written by
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.An M. Warner Losh Aq Mt imp@FreeBSD.org .
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