Change the SCSI INQUIRY peripheral qualifier that CTL reports for LUNs

that don't exist.

Anecdotal evidence indicates that it is better to return 011b (bad LUN)
than 001b (LUN offline).  However, this change also gives the user a
sysctl/tunable, kern.cam.ctl.inquiry_pq_no_lun, to override the change
and return to the previous behavior.  (The previous behavior was to
return 001b, or LUN offline.)

ctl.c:		Change the default inquiry peripheral qualifier to 011b,
		and add a sysctl and tunable to allow the user to change
		it back to 001b if needed.

		Don't insert a Copan copyright statement in the inquiry
		data.  The copyright statements on the files are
		sufficient.

ctl_private.h:	Add sysctl variable context to the CTL softc.

ctl_cmd_table.c,
ctl_frontend_internal.c,
ctl_frontend.c,
ctl_backend.c,
ctl_error.c:	Include sys/sysctl.h.

MFC after:	3 days

sys/cam/ctl/ctl.c

@@ -959,6 +959,33 @@ ctl_init(void)
 
 	softc->dev->si_drv1 = softc;
 
+	/*
+	 * By default, return a "bad LUN" peripheral qualifier for unknown
+	 * LUNs.  The user can override this default using the tunable or
+	 * sysctl.  See the comment in ctl_inquiry_std() for more details.
+	 */
+	softc->inquiry_pq_no_lun = 1;
+	TUNABLE_INT_FETCH("kern.cam.ctl.inquiry_pq_no_lun",
+			  &softc->inquiry_pq_no_lun);
+	sysctl_ctx_init(&softc->sysctl_ctx);
+	softc->sysctl_tree = SYSCTL_ADD_NODE(&softc->sysctl_ctx,
+		SYSCTL_STATIC_CHILDREN(_kern_cam), OID_AUTO, "ctl",
+		CTLFLAG_RD, 0, "CAM Target Layer");
+
+	if (softc->sysctl_tree == NULL) {
+		printf("%s: unable to allocate sysctl tree\n", __func__);
+		destroy_dev(softc->dev);
+		free(control_softc, M_DEVBUF);
+		control_softc = NULL;
+		return;
+	}
+
+	SYSCTL_ADD_INT(&softc->sysctl_ctx,
+		       SYSCTL_CHILDREN(softc->sysctl_tree), OID_AUTO,
+		       "inquiry_pq_no_lun", CTLFLAG_RW,
+		       &softc->inquiry_pq_no_lun, 0,
+		       "Report no lun possible for invalid LUNs");
+
 	mtx_init(&softc->ctl_lock, "CTL mutex", NULL, MTX_DEF);
 	softc->open_count = 0;
 
@@ -1150,6 +1177,11 @@ ctl_shutdown(void)
 
 	destroy_dev(softc->dev);
 
+	sysctl_ctx_free(&softc->sysctl_ctx);
+
+	free(control_softc, M_DEVBUF);
+	control_softc = NULL;
+
 	printf("ctl: CAM Target Layer unloaded\n");
 }
 
@@ -9369,15 +9401,55 @@ ctl_inquiry_std(struct ctl_scsiio *ctsio)
 	memset(inq_ptr, 0, sizeof(*inq_ptr));
 
 	/*
-	 * The control device is always connected.  The disk device, on the
-	 * other hand, may not be online all the time.  If we don't have a
-	 * LUN mapping, we'll just say it's offline.
+	 * If we have a LUN configured, report it as connected.  Otherwise,
+	 * report that it is offline or no device is supported, depending 
+	 * on the value of inquiry_pq_no_lun.
+	 *
+	 * According to the spec (SPC-4 r34), the peripheral qualifier
+	 * SID_QUAL_LU_OFFLINE (001b) is used in the following scenario:
+	 *
+	 * "A peripheral device having the specified peripheral device type 
+	 * is not connected to this logical unit. However, the device
+	 * server is capable of supporting the specified peripheral device
+	 * type on this logical unit."
+	 *
+	 * According to the same spec, the peripheral qualifier
+	 * SID_QUAL_BAD_LU (011b) is used in this scenario:
+	 *
+	 * "The device server is not capable of supporting a peripheral
+	 * device on this logical unit. For this peripheral qualifier the
+	 * peripheral device type shall be set to 1Fh. All other peripheral
+	 * device type values are reserved for this peripheral qualifier."
+	 *
+	 * Given the text, it would seem that we probably want to report that
+	 * the LUN is offline here.  There is no LUN connected, but we can
+	 * support a LUN at the given LUN number.
+	 *
+	 * In the real world, though, it sounds like things are a little
+	 * different:
+	 *
+	 * - Linux, when presented with a LUN with the offline peripheral
+	 *   qualifier, will create an sg driver instance for it.  So when
+	 *   you attach it to CTL, you wind up with a ton of sg driver
+	 *   instances.  (One for every LUN that Linux bothered to probe.)
+	 *   Linux does this despite the fact that it issues a REPORT LUNs
+	 *   to LUN 0 to get the inventory of supported LUNs.
+	 *
+	 * - There is other anecdotal evidence (from Emulex folks) about
+	 *   arrays that use the offline peripheral qualifier for LUNs that
+	 *   are on the "passive" path in an active/passive array.
+	 *
+	 * So the solution is provide a hopefully reasonable default
+	 * (return bad/no LUN) and allow the user to change the behavior
+	 * with a tunable/sysctl variable.
 	 */
 	if (lun != NULL)
 		inq_ptr->device = (SID_QUAL_LU_CONNECTED << 5) |
 				  lun->be_lun->lun_type;
-	else
+	else if (ctl_softc->inquiry_pq_no_lun == 0)
 		inq_ptr->device = (SID_QUAL_LU_OFFLINE << 5) | T_DIRECT;
+	else
+		inq_ptr->device = (SID_QUAL_BAD_LU << 5) | T_NODEVICE;
 
 	/* RMB in byte 2 is 0 */
 	inq_ptr->version = SCSI_REV_SPC3;
@@ -9491,8 +9563,6 @@ ctl_inquiry_std(struct ctl_scsiio *ctsio)
 			break;
 		}
 	}
-	sprintf((char *)inq_ptr->vendor_specific1, "Copyright (C) 2004, COPAN "
-		"Systems, Inc.  All Rights Reserved.");
 
 	ctsio->scsi_status = SCSI_STATUS_OK;
 	if (ctsio->kern_data_len > 0) {

sys/cam/ctl/ctl_backend.c

@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mutex.h>
 #include <sys/condvar.h>
 #include <sys/queue.h>
+#include <sys/sysctl.h>
 
 #include <cam/scsi/scsi_all.h>
 #include <cam/scsi/scsi_da.h>

sys/cam/ctl/ctl_cmd_table.c

@@ -44,6 +44,7 @@
 #include <sys/malloc.h>
 #include <sys/condvar.h>
 #include <sys/queue.h>
+#include <sys/sysctl.h>
 
 #include <cam/scsi/scsi_all.h>
 #include <cam/scsi/scsi_da.h>

sys/cam/ctl/ctl_error.c

@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/condvar.h>
 #include <sys/stddef.h>
 #include <sys/ctype.h>
+#include <sys/sysctl.h>
 #include <machine/stdarg.h>
 
 #include <cam/scsi/scsi_all.h>

sys/cam/ctl/ctl_frontend.c

@@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/condvar.h>
 #include <sys/endian.h>
 #include <sys/queue.h>
+#include <sys/sysctl.h>
 
 #include <cam/scsi/scsi_all.h>
 #include <cam/scsi/scsi_da.h>

sys/cam/ctl/ctl_frontend_internal.c

@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/condvar.h>
 #include <sys/queue.h>
 #include <sys/sbuf.h>
+#include <sys/sysctl.h>
 #include <cam/scsi/scsi_all.h>
 #include <cam/scsi/scsi_da.h>
 #include <cam/ctl/ctl_io.h>

sys/cam/ctl/ctl_private.h

@@ -421,6 +421,9 @@ struct ctl_softc {
 	int num_luns;
 	ctl_gen_flags flags;
 	ctl_ha_mode ha_mode;
+	int inquiry_pq_no_lun;
+	struct sysctl_ctx_list sysctl_ctx;
+	struct sysctl_oid *sysctl_tree;
 	struct ctl_ioctl_info ioctl_info;
 	struct ctl_lun lun;
 	struct ctl_io_pool *internal_pool;