scsi_transport_srp: Add rport state diagram

Add a diagram in Documentation/scsi/scsi_transport_srp that
illustrates the rport state transitions.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>

Documentation/scsi/scsi_transport_srp/Makefile

+all: rport_state_diagram.svg rport_state_diagram.png
+
+rport_state_diagram.svg: rport_state_diagram.dot
+	dot -Tsvg -o $@ $<
+
+rport_state_diagram.png: rport_state_diagram.dot
+	dot -Tpng -o $@ $<

Documentation/scsi/scsi_transport_srp/rport_state_diagram.dot

+digraph srp_initiator {
+	node [shape = doublecircle]; running lost;
+	node [shape = circle];
+
+	{
+	  rank = min;
+	  running_rta	[ label = "running;\nreconnect\ntimer\nactive" ];
+	};
+	running		[ label = "running;\nreconnect\ntimer\nstopped" ];
+	blocked;
+	failfast	[ label = "fail I/O\nfast" ];
+	lost;
+
+	running -> running_rta		[ label = "fast_io_fail_tmo = off and\ndev_loss_tmo = off;\nsrp_start_tl_fail_timers()" ];
+	running_rta -> running		[ label = "fast_io_fail_tmo = off and\ndev_loss_tmo = off;\nreconnecting succeeded" ];
+	running -> blocked		[ label = "fast_io_fail_tmo >= 0 or\ndev_loss_tmo >= 0;\nsrp_start_tl_fail_timers()" ];
+	running -> failfast		[ label = "fast_io_fail_tmo = off and\ndev_loss_tmo = off;\nreconnecting failed\n" ];
+	blocked -> failfast		[ label = "fast_io_fail_tmo\nexpired or\nreconnecting\nfailed" ];
+	blocked -> lost			[ label = "dev_loss_tmo\nexpired or\nsrp_stop_rport_timers()" ];
+	failfast -> lost		[ label = "dev_loss_tmo\nexpired or\nsrp_stop_rport_timers()" ];
+	blocked -> running		[ label = "reconnecting\nsucceeded" ];
+	failfast -> failfast		[ label = "reconnecting\nfailed" ];
+	failfast -> running		[ label = "reconnecting\nsucceeded" ];
+	running -> lost			[ label = "srp_stop_rport_timers()" ];
+	running_rta -> lost		[ label = "srp_stop_rport_timers()" ];
+}