Devd event from GEOM?

[Robert Watson]

On Sun, 23 Jan 2005, Pete Carah wrote:

> Geom doesn't feed node-creations to devd in 5.3.  This would be VERY
> useful for letting ordinary non-programmer users access pen drives,
> among other things (floppies come to mind too...).  (or mount e.g. a pen
> drive as part of an authentication system where no-one is yet logged in,
> so can't manually mount...) 
> 
> umass0 comes in to devd, but this isn't useful for use in "mount".  One
> needs the disk device nodes.  I suppose one *could* parse dmesg for the
> info (or maybe sysctl) but that smacks of a serious kluge.  (not to
> mention that the slice table isn't represented in dmesg anyhow, and
> practically nothing is in sysctl...) 
> 
> Does this yet happen in any later version (RELENG_5 or HEAD)?  If not,
> is there anyone planning or working on it? 
> 
> It *does* work in Solaris and IRIX, (I know - we aren't them...)  I
> don't know about any Linux or other *BSD version either. 
> 
> Geom is modular enough that this shouldn't be difficult... 

I used the attached patches do announce storage device arrival on my
notebook so that I can do auto-mounting of USB storage.  There appears to
be some disagreement regarding layering: my opinion has generally been
that since there are multiple layers involved, we should announce both the
layer and the device, for example:

  Network stack says "ifnet fxp0 arrived"

separately from:

  /dev says "/dev/net/fxp0 arrived"

Since they constitute different "things" with quite different management
properties.  This also provides additional contextual information: rather
than devd having to guess what type of object a device node is using name
matching, by learning about it through geom or the network stack, it knows
what kind it is up front in a strong way. 

Robert N M Watson


Index: geom.h
===================================================================
RCS file: /home/ncvs/src/sys/geom/geom.h,v
retrieving revision 1.90
diff -u -r1.90 geom.h
--- geom.h	21 Dec 2004 18:32:46 -0000	1.90
+++ geom.h	22 Dec 2004 18:43:59 -0000
@@ -200,6 +200,10 @@
 void g_dev_print(void);
 struct g_provider *g_dev_getprovider(struct cdev *dev);
 
+/* geom_devctl.c */
+void g_dev_added(const char *);
+void g_dev_removed(const char *);
+
 /* geom_dump.c */
 void g_trace(int level, const char *, ...);
 #	define G_T_TOPOLOGY	1
Index: geom_dev.c
===================================================================
RCS file: /home/ncvs/src/sys/geom/geom_dev.c,v
retrieving revision 1.87
diff -u -r1.87 geom_dev.c
--- geom_dev.c	12 Dec 2004 10:09:05 -0000	1.87
+++ geom_dev.c	22 Dec 2004 18:43:59 -0000
@@ -151,6 +151,7 @@
 	    UID_ROOT, GID_OPERATOR, 0640, gp->name);
 	if (pp->flags & G_PF_CANDELETE)
 		dev->si_flags |= SI_CANDELETE;
+	g_dev_added(gp->name);
 	mtx_unlock(&Giant);
 	g_topology_lock();
 	dev->si_iosize_max = MAXPHYS;
@@ -415,6 +416,9 @@
 	destroy_dev(dev);
 	free_unr(unithdr, unit);
 
+	/* Send a note to userspace for any cleanup it wants to do. */
+	g_dev_removed(gp->name);
+
 	/* Wait for the cows to come home */
 	while (cp->nstart != cp->nend)
 		msleep(&dev, NULL, PRIBIO, "gdevorphan", hz / 10);
Index: geom_devctl.c
===================================================================
RCS file: geom_devctl.c
diff -N geom_devctl.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ geom_devctl.c	18 Feb 2004 00:26:23 -0000
@@ -0,0 +1,66 @@
+/*-
+ * Copyright (c) 2004 Robert N. M. Watson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * GEOM disk event stream for userspace: notification of arrival and
+ * deletion of GEOM-visible /dev entries.
+ */
+
+#include <sys/param.h>
+#include <sys/bus.h>
+#include <sys/malloc.h>
+#include <sys/sbuf.h>
+#include <sys/systm.h>
+
+#include <geom/geom.h>
+
+void
+g_dev_added(const char *disk)
+{
+	struct sbuf sb;
+
+	sbuf_new(&sb, NULL, 0, SBUF_AUTOEXTEND);
+	sbuf_printf(&sb, "+%s at  on geom", disk);
+	sbuf_finish(&sb);
+	devctl_queue_data(sbuf_data(&sb));
+	printf("geom: sent devctl '%s'\n", sbuf_data(&sb));
+	sbuf_done(&sb);
+}
+
+void
+g_dev_removed(const char *disk)
+{
+	struct sbuf sb;
+
+	sbuf_new(&sb, NULL, 0, SBUF_AUTOEXTEND);
+	sbuf_printf(&sb, "-%s at  on geom", disk);
+	sbuf_finish(&sb);
+	devctl_queue_data(sbuf_data(&sb));
+	printf("geom: sent devctl '%s'\n", sbuf_data(&sb));
+	sbuf_done(&sb);
+}