move forward with scsi multipathing.

the big change is how paths between mpath capable devices and the
kernel are managed.

originally the midlayer would steal the links to the devices and
hide them behind mpath. all the changes an adapter made to a link
(eg activate or detach), the midlayer had to test if it was an mpath
link and then call special mpath code to handle it.

the original code also assumed that all paths behaved the same, but
the reality is that different devices have different command sets
and behaviours. figuring out which behaviour to pick and prioritising
them is basically the same job autoconf does with match and attach.

rather than special casing mpath in the midlayer and reimplimenting
autoconf, this turns paths into actual device drivers with match
and attach routines. after they figure out if the path is active,
they then give it to mpath(4) to use as a backend.

i have written drivers for symmetric access devices (sym(4)) where
all paths to the same logical unit are as good as each other,
lsi/engenio arrays (rdac(4), and emc arrays (emc(4)).

the rdac and emc drivers only detect active paths at attach time,
the do not cope if the controller changes state unless you unplug
the path and plug it in again to retest the active state. they also
do not have support for directing array failover.

operating and hoplugging has been tested with mpii(4), fc and sas
mpi(4), and iscsi via vscsi (claudio did this too).

ok krw@ deraadt@

1 files changed, 55 insertions, 0 deletions

diff --git a/sys/scsi/mpathvar.h b/sys/scsi/mpathvar.h
new file mode 100644
index 00000000000..8a1357a500b
--- /dev/null
+++ b/sys/scsi/mpathvar.h
@@ -0,0 +1,55 @@
+/*	$OpenBSD: mpathvar.h,v 1.1 2011/04/05 14:25:42 dlg Exp $ */
+
+/*
+ * Copyright (c) 2010 David Gwynne <dlg@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _SYS_SCSI_MPATH_H_
+#define _SYS_SCSI_MPATH_H_
+
+struct mpath_dev;
+struct mpath_group;
+
+struct mpath_ops {
+	char	op_name[16];
+	void	(*op_start)(struct scsi_xfer *);
+	int	(*op_checksense)(struct scsi_xfer *);
+	int	(*op_online)(struct scsi_link *);
+	int	(*op_offline)(struct scsi_link *);
+};
+
+struct mpath_path {
+	/* the path driver must set these */
+	struct scsi_xshandler	 p_xsh;
+	struct scsi_link	*p_link;
+	struct mpath_ops	*p_ops;
+	int			 p_gid;
+
+	/* the follwoing are private to mpath.c */
+	TAILQ_ENTRY(mpath_path)	 p_entry;
+	struct mpath_dev	*p_dev;
+	int			 p_state;
+};
+
+int			 mpath_path_probe(struct scsi_link *);
+int			 mpath_path_attach(struct mpath_path *);
+void			 mpath_path_state(struct mpath_path *, int);
+int			 mpath_path_detach(struct mpath_path *);
+
+void			 mpath_start(struct mpath_path *, struct scsi_xfer *);
+
+struct device		*mpath_bootdv(struct device *);
+
+#endif /* _SYS_SCSI_MPATH_H_ */