make ntpd listen on the hotplug socket and decode yadda yadda, because

new sensors showing up will be announced that way when slacking ml comes
back from food

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.72 2006/05/27 18:32:00 henning Exp $ */
+/*	$OpenBSD: ntp.c,v 1.73 2006/05/27 21:27:34 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -35,7 +35,8 @@
 #include "ntp.h"
 
 #define	PFD_PIPE_MAIN	0
-#define	PFD_MAX		1
+#define	PFD_HOTPLUG	1
+#define	PFD_MAX		2
 
 volatile sig_atomic_t	 ntp_quit = 0;
 struct imsgbuf		*ibuf_main;
@@ -62,7 +63,8 @@ ntp_sighdlr(int sig)
 pid_t
 ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 {
-	int			 a, b, nfds, i, j, idx_peers, timeout, nullfd;
+	int			 a, b, nfds, i, j, idx_peers, timeout;
+	int			 hotplugfd, nullfd;
 	u_int			 pfd_elms = 0, idx2peer_elms = 0;
 	u_int			 listener_cnt, new_cnt, sent_cnt, trial_cnt;
 	u_int			 sensors_cnt = 0;
@@ -97,6 +99,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 
 	if ((nullfd = open(_PATH_DEVNULL, O_RDWR, 0)) == -1)
 		fatal(NULL);
+	hotplugfd = sensor_hotplugfd();
 
 	if (stat(pw->pw_dir, &stb) == -1)
 		fatal("stat");
@@ -187,6 +190,8 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 		nextaction = time(NULL) + 3600;
 		pfd[PFD_PIPE_MAIN].fd = ibuf_main->fd;
 		pfd[PFD_PIPE_MAIN].events = POLLIN;
+		pfd[PFD_HOTPLUG].fd = hotplugfd;
+		pfd[PFD_HOTPLUG].events = POLLIN;
 
 		i = PFD_MAX;
 		TAILQ_FOREACH(la, &conf->listen_addrs, entry) {
@@ -272,6 +277,11 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 				ntp_quit = 1;
 		}
 
+		if (nfds > 0 && pfd[PFD_HOTPLUG].revents & (POLLIN|POLLERR)) {
+			nfds--;
+			sensor_hotplugevent(hotplugfd);
+		}
+
 		for (j = 1; nfds > 0 && j < idx_peers; j++)
 			if (pfd[j].revents & (POLLIN|POLLERR)) {
 				nfds--;

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.65 2006/05/27 18:32:00 henning Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.66 2006/05/27 21:27:34 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -285,3 +285,5 @@ void			sensor_init(struct ntpd_conf *);
 void			sensor_scan(struct ntpd_conf *);
 void			sensor_remove(struct ntpd_conf *, struct ntp_sensor *);
 int			sensor_query(struct ntp_sensor *);
+int			sensor_hotplugfd(void);
+void			sensor_hotplugevent(int);

src/usr.sbin/ntpd/sensors.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: sensors.c,v 1.2 2006/05/27 17:01:07 henning Exp $ */
+/*	$OpenBSD: sensors.c,v 1.3 2006/05/27 21:27:34 henning Exp $ */
 
 /*
  * Copyright (c) 2006 Henning Brauer <henning@openbsd.org>
@@ -20,6 +20,8 @@
 #include <sys/queue.h>
 #include <sys/sensors.h>
 #include <sys/sysctl.h>
+#include <sys/device.h>
+#include <sys/hotplug.h>
 
 #include <errno.h>
 #include <fcntl.h>
@@ -30,6 +32,7 @@
 #include "ntpd.h"
 
 #define SENSORS_MAX	255
+#define	_PATH_DEV_HOTPLUG               "/dev/hotplug"
 
 void	sensor_add(struct ntpd_conf *, struct sensor *);
 
@@ -150,3 +153,41 @@ sensor_query(struct ntp_sensor *s)
 
 	return (0);
 }
+
+int
+sensor_hotplugfd(void)
+{
+	int	fd, flags;
+
+	if ((fd = open(_PATH_DEV_HOTPLUG, O_RDONLY, 0)) == -1)
+		fatal(NULL);
+
+	if ((flags = fcntl(fd, F_GETFL, 0)) == -1)
+		fatal("fnctl F_GETFL");
+	flags |= O_NONBLOCK;
+	if ((flags = fcntl(fd, F_SETFL, flags)) == -1)
+		fatal("fnctl F_SETFL");
+
+	return (fd);
+}
+
+void
+sensor_hotplugevent(int fd)
+{
+	struct hotplug_event	he;
+	ssize_t			n;
+
+	do {
+		if ((n = read(fd, &he, sizeof(he))) == -1 &&
+		    errno != EINTR && errno != EAGAIN)
+			fatal("sensor_hotplugevent read");
+
+		if (n == sizeof(he))
+			switch (he.he_type) {
+			default:		/* ignore */
+				break;
+			}
+		else if (n > 0)
+			fatal("sensor_hotplugevent: short read");
+	} while (n > 0 || (n == -1 && errno == EINTR));
+}