CONFIG_INTRHOOK(9)     FreeBSD Kernel Developer's Manual    CONFIG_INTRHOOK(9)

NAME
     config_intrhook - schedule a function to be run after interrupts have
     been enabled, but before root is mounted

SYNOPSIS
     #include <sys/kernel.h>

     typedef void (*ich_func_t)(void *arg);)(void *arg);

     int
     config_intrhook_establish(struct intr_config_hook *hook);

     void
     config_intrhook_disestablish(struct intr_config_hook *hook);

     int
     config_intrhook_drain(struct intr_config_hook *hook);

     void
     config_intrhook_oneshot(ich_func_t func, void *arg);

DESCRIPTION
     The config_intrhook_establish() function schedules a function to be run
     after interrupts have been enabled, but before root is mounted.  If the
     system has already passed this point in its initialization, the function
     is called immediately.

     The config_intrhook_disestablish() function removes the entry from the
     hook queue.

     The config_intrhook_drain() function removes the entry from the hook
     queue in a safe way.  If the hook is not currently active it removes hook
     from the hook queue and returns ICHS_QUEUED.  If the hook is active, it
     waits for the hook to complete before returning ICHS_RUNNING.  If the
     hook has previously completed, it returns ICHS_DONE.  Because a
     config_intrhook is undefined prior to config_intrhook_establish(), this
     function may only be called after that function has returned.

     The config_intrhook_oneshot() function schedules a function to be run as
     described for config_intrhook_establish(); the entry is automatically
     removed from the hook queue after that function runs.  This is
     appropriate when additional device configuration must be done after
     interrupts are enabled, but there is no need to stall the boot process
     after that.  This function allocates memory using M_WAITOK; do not call
     this while holding any non-sleepable locks.

     Before root is mounted, all the previously established hooks are run.
     The boot process is then stalled until all handlers remove their hook
     from the hook queue with config_intrhook_disestablish().  The boot
     process then proceeds to attempt to mount the root file system.  Any
     driver that can potentially provide devices they wish to be mounted as
     root must use either this hook, or probe all these devices in the initial
     probe.  Since interrupts are disabled during the probe process, many
     drivers need a method to probe for devices with interrupts enabled.

     The requests are made with the intr_config_hook structure.  This
     structure is defined as follows:

     struct intr_config_hook {
             TAILQ_ENTRY(intr_config_hook) ich_links;/* Private */
             ich_func_t      ich_func;               /* function to call */
             void            *ich_arg;               /* Argument to call */
     };

     Storage for the intr_config_hook structure must be provided by the
     driver.  It must be stable from just before the hook is established until
     after the hook is disestablished.

     Specifically, hooks are run at SI_SUB_INT_CONFIG_HOOKS(), which is
     immediately after the scheduler is started, and just before the root file
     system device is discovered.

RETURN VALUES
     A zero return value means the hook was successfully added to the queue
     (with either deferred or immediate execution).  A non-zero return value
     means the hook could not be added to the queue because it was already on
     the queue.

SEE ALSO
     DEVICE_ATTACH(9)

HISTORY
     These functions were introduced in FreeBSD 3.0 with the CAM subsystem,
     but are available for any driver to use.

AUTHORS
     The functions were written by Justin Gibbs <gibbs@FreeBSD.org>.  This
     manual page was written by M. Warner Losh <imp@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6          March 8, 2021         FreeBSD 13.1-RELEASE-p6