Add config_intrhook_oneshot(): schedule an intrhook function and unregister

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

share/man/man9/Makefile

@@ -669,7 +669,8 @@ MLINKS+=condvar.9 cv_broadcast.9 \
 	condvar.9 cv_wait_unlock.9 \
 	condvar.9 cv_wmesg.9
 MLINKS+=config_intrhook.9 config_intrhook_disestablish.9 \
-	config_intrhook.9 config_intrhook_establish.9
+	config_intrhook.9 config_intrhook_establish.9 \
+	config_intrhook.9 config_intrhook_oneshot.9
 MLINKS+=contigmalloc.9 contigfree.9
 MLINKS+=casuword.9 casueword.9 \
 	casuword.9 casueword32.9 \

share/man/man9/config_intrhook.9

@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 24, 2006
+.Dd August 10, 2017
 .Dt CONFIG_INTRHOOK 9
 .Os
 .Sh NAME
@@ -35,10 +35,13 @@
 but before root is mounted
 .Sh SYNOPSIS
 .In sys/kernel.h
+.Vt typedef void (*ich_func_t)(void *arg);
 .Ft int
 .Fn config_intrhook_establish "struct intr_config_hook *hook"
 .Ft void
 .Fn config_intrhook_disestablish "struct intr_config_hook *hook"
+.Ft void
+.Fn config_intrhook_oneshot "ich_func_t func" "void *arg"
 .Sh DESCRIPTION
 The
 .Fn config_intrhook_establish
@@ -51,6 +54,18 @@ The
 .Fn config_intrhook_disestablish
 function removes the entry from the hook queue.
 .Pp
+The
+.Fn config_intrhook_oneshot
+function schedules a function to be run as described for
+.Fn 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.
+.Pp
 Before root is mounted, all the previously established hooks are
 run.
 The boot process is then stalled until all handlers remove their hook
@@ -71,8 +86,8 @@ This structure is defined as follows:
 .Bd -literal
 struct intr_config_hook {
 	TAILQ_ENTRY(intr_config_hook) ich_links;/* Private */
-	void	(*ich_func)(void *arg);		/* function to call */
-	void	*ich_arg;			/* Argument to call */
+	ich_func_t	ich_func;		/* function to call */
+	void		*ich_arg;		/* Argument to call */
 };
 .Ed
 .Pp

sys/kern/subr_autoconf.c

@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/kernel.h>
 #include <sys/linker.h>
 #include <sys/lock.h>
+#include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/systm.h>
 
@@ -62,6 +63,27 @@ MTX_SYSINIT(intr_config_hook, &intr_config_hook_lock, "intr config", MTX_DEF);
 /* ARGSUSED */
 static void run_interrupt_driven_config_hooks(void);
 
+/*
+ * Private data and a shim function for implementing config_interhook_oneshot().
+ */
+struct oneshot_config_hook {
+	struct intr_config_hook 
+			och_hook;		/* Must be first */
+	ich_func_t	och_func;
+	void		*och_arg;
+};
+
+static void
+config_intrhook_oneshot_func(void *arg)
+{
+	struct oneshot_config_hook *ohook;
+
+	ohook = arg;
+	ohook->och_func(ohook->och_arg);
+	config_intrhook_disestablish(&ohook->och_hook);
+	free(ohook, M_DEVBUF);
+}
+
 /*
  * If we wait too long for an interrupt-driven config hook to return, print
  * a diagnostic.
@@ -183,6 +205,22 @@ config_intrhook_establish(struct intr_config_hook *hook)
 	return (0);
 }
 
+/*
+ * Register a hook function that is automatically unregistered after it runs.
+ */
+void
+config_intrhook_oneshot(ich_func_t func, void *arg)
+{
+	struct oneshot_config_hook *ohook;
+
+	ohook = malloc(sizeof(*ohook), M_DEVBUF, M_WAITOK);
+	ohook->och_func = func;
+	ohook->och_arg  = arg;
+	ohook->och_hook.ich_func = config_intrhook_oneshot_func;
+	ohook->och_hook.ich_arg  = ohook;
+	config_intrhook_establish(&ohook->och_hook);
+}
+
 void
 config_intrhook_disestablish(struct intr_config_hook *hook)
 {

sys/sys/kernel.h

@@ -400,13 +400,16 @@ struct tunable_str {
 #define	TUNABLE_STR_FETCH(path, var, size)			\
 	getenv_string((path), (var), (size))
 
+typedef void (*ich_func_t)(void *_arg);
+
 struct intr_config_hook {
 	TAILQ_ENTRY(intr_config_hook) ich_links;
-	void	(*ich_func)(void *arg);
-	void	*ich_arg;
+	ich_func_t	ich_func;
+	void		*ich_arg;
 };
 
 int	config_intrhook_establish(struct intr_config_hook *hook);
 void	config_intrhook_disestablish(struct intr_config_hook *hook);
+void	config_intrhook_oneshot(ich_func_t _func, void *_arg);
 
 #endif /* !_SYS_KERNEL_H_*/