2 * S/390 common I/O routines -- low level i/o calls
4 * Copyright IBM Corp. 1999, 2008
5 * Author(s): Ingo Adlung (adlung@de.ibm.com)
6 * Cornelia Huck (cornelia.huck@de.ibm.com)
7 * Arnd Bergmann (arndb@de.ibm.com)
8 * Martin Schwidefsky (schwidefsky@de.ibm.com)
11 #define KMSG_COMPONENT "cio"
12 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
14 #include <linux/ftrace.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/slab.h>
18 #include <linux/device.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/interrupt.h>
22 #include <asm/delay.h>
24 #include <asm/irq_regs.h>
25 #include <asm/setup.h>
26 #include <asm/reset.h>
28 #include <asm/chpid.h>
31 #include <asm/cputime.h>
40 #include "blacklist.h"
41 #include "cio_debug.h"
44 debug_info_t *cio_debug_msg_id;
45 debug_info_t *cio_debug_trace_id;
46 debug_info_t *cio_debug_crw_id;
49 * Function: cio_debug_init
50 * Initializes three debug logs for common I/O:
51 * - cio_msg logs generic cio messages
52 * - cio_trace logs the calling of different functions
53 * - cio_crw logs machine check related cio messages
55 static int __init cio_debug_init(void)
57 cio_debug_msg_id = debug_register("cio_msg", 16, 1, 16 * sizeof(long));
58 if (!cio_debug_msg_id)
60 debug_register_view(cio_debug_msg_id, &debug_sprintf_view);
61 debug_set_level(cio_debug_msg_id, 2);
62 cio_debug_trace_id = debug_register("cio_trace", 16, 1, 16);
63 if (!cio_debug_trace_id)
65 debug_register_view(cio_debug_trace_id, &debug_hex_ascii_view);
66 debug_set_level(cio_debug_trace_id, 2);
67 cio_debug_crw_id = debug_register("cio_crw", 16, 1, 16 * sizeof(long));
68 if (!cio_debug_crw_id)
70 debug_register_view(cio_debug_crw_id, &debug_sprintf_view);
71 debug_set_level(cio_debug_crw_id, 4);
76 debug_unregister(cio_debug_msg_id);
77 if (cio_debug_trace_id)
78 debug_unregister(cio_debug_trace_id);
80 debug_unregister(cio_debug_crw_id);
84 arch_initcall (cio_debug_init);
86 int cio_set_options(struct subchannel *sch, int flags)
88 struct io_subchannel_private *priv = to_io_private(sch);
90 priv->options.suspend = (flags & DOIO_ALLOW_SUSPEND) != 0;
91 priv->options.prefetch = (flags & DOIO_DENY_PREFETCH) != 0;
92 priv->options.inter = (flags & DOIO_SUPPRESS_INTER) != 0;
97 cio_start_handle_notoper(struct subchannel *sch, __u8 lpm)
106 CIO_MSG_EVENT(2, "cio_start: 'not oper' status for "
107 "subchannel 0.%x.%04x!\n", sch->schid.ssid,
110 if (cio_update_schib(sch))
113 sprintf(dbf_text, "no%s", dev_name(&sch->dev));
114 CIO_TRACE_EVENT(0, dbf_text);
115 CIO_HEX_EVENT(0, &sch->schib, sizeof (struct schib));
117 return (sch->lpm ? -EACCES : -ENODEV);
121 cio_start_key (struct subchannel *sch, /* subchannel structure */
122 struct ccw1 * cpa, /* logical channel prog addr */
123 __u8 lpm, /* logical path mask */
124 __u8 key) /* storage key */
126 struct io_subchannel_private *priv = to_io_private(sch);
127 union orb *orb = &priv->orb;
130 CIO_TRACE_EVENT(5, "stIO");
131 CIO_TRACE_EVENT(5, dev_name(&sch->dev));
133 memset(orb, 0, sizeof(union orb));
134 /* sch is always under 2G. */
135 orb->cmd.intparm = (u32)(addr_t)sch;
138 orb->cmd.pfch = priv->options.prefetch == 0;
139 orb->cmd.spnd = priv->options.suspend;
140 orb->cmd.ssic = priv->options.suspend && priv->options.inter;
141 orb->cmd.lpm = (lpm != 0) ? lpm : sch->lpm;
144 * for 64 bit we always support 64 bit IDAWs with 4k page size only
149 orb->cmd.key = key >> 4;
150 /* issue "Start Subchannel" */
151 orb->cmd.cpa = (__u32) __pa(cpa);
152 ccode = ssch(sch->schid, orb);
154 /* process condition code */
155 CIO_HEX_EVENT(5, &ccode, sizeof(ccode));
160 * initialize device status information
162 sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
164 case 1: /* status pending */
167 case 3: /* device/path not operational */
168 return cio_start_handle_notoper(sch, lpm);
175 cio_start (struct subchannel *sch, struct ccw1 *cpa, __u8 lpm)
177 return cio_start_key(sch, cpa, lpm, PAGE_DEFAULT_KEY);
181 * resume suspended I/O operation
184 cio_resume (struct subchannel *sch)
188 CIO_TRACE_EVENT(4, "resIO");
189 CIO_TRACE_EVENT(4, dev_name(&sch->dev));
191 ccode = rsch (sch->schid);
193 CIO_HEX_EVENT(4, &ccode, sizeof(ccode));
197 sch->schib.scsw.cmd.actl |= SCSW_ACTL_RESUME_PEND;
205 * useless to wait for request completion
206 * as device is no longer operational !
216 cio_halt(struct subchannel *sch)
223 CIO_TRACE_EVENT(2, "haltIO");
224 CIO_TRACE_EVENT(2, dev_name(&sch->dev));
227 * Issue "Halt subchannel" and process condition code
229 ccode = hsch (sch->schid);
231 CIO_HEX_EVENT(2, &ccode, sizeof(ccode));
235 sch->schib.scsw.cmd.actl |= SCSW_ACTL_HALT_PEND;
237 case 1: /* status pending */
240 default: /* device not operational */
246 * Clear I/O operation
249 cio_clear(struct subchannel *sch)
256 CIO_TRACE_EVENT(2, "clearIO");
257 CIO_TRACE_EVENT(2, dev_name(&sch->dev));
260 * Issue "Clear subchannel" and process condition code
262 ccode = csch (sch->schid);
264 CIO_HEX_EVENT(2, &ccode, sizeof(ccode));
268 sch->schib.scsw.cmd.actl |= SCSW_ACTL_CLEAR_PEND;
270 default: /* device not operational */
276 * Function: cio_cancel
277 * Issues a "Cancel Subchannel" on the specified subchannel
278 * Note: We don't need any fancy intparms and flags here
279 * since xsch is executed synchronously.
280 * Only for common I/O internal use as for now.
283 cio_cancel (struct subchannel *sch)
290 CIO_TRACE_EVENT(2, "cancelIO");
291 CIO_TRACE_EVENT(2, dev_name(&sch->dev));
293 ccode = xsch (sch->schid);
295 CIO_HEX_EVENT(2, &ccode, sizeof(ccode));
298 case 0: /* success */
299 /* Update information in scsw. */
300 if (cio_update_schib(sch))
303 case 1: /* status pending */
305 case 2: /* not applicable */
307 default: /* not oper */
313 static void cio_apply_config(struct subchannel *sch, struct schib *schib)
315 schib->pmcw.intparm = sch->config.intparm;
316 schib->pmcw.mbi = sch->config.mbi;
317 schib->pmcw.isc = sch->config.isc;
318 schib->pmcw.ena = sch->config.ena;
319 schib->pmcw.mme = sch->config.mme;
320 schib->pmcw.mp = sch->config.mp;
321 schib->pmcw.csense = sch->config.csense;
322 schib->pmcw.mbfc = sch->config.mbfc;
323 if (sch->config.mbfc)
324 schib->mba = sch->config.mba;
327 static int cio_check_config(struct subchannel *sch, struct schib *schib)
329 return (schib->pmcw.intparm == sch->config.intparm) &&
330 (schib->pmcw.mbi == sch->config.mbi) &&
331 (schib->pmcw.isc == sch->config.isc) &&
332 (schib->pmcw.ena == sch->config.ena) &&
333 (schib->pmcw.mme == sch->config.mme) &&
334 (schib->pmcw.mp == sch->config.mp) &&
335 (schib->pmcw.csense == sch->config.csense) &&
336 (schib->pmcw.mbfc == sch->config.mbfc) &&
337 (!sch->config.mbfc || (schib->mba == sch->config.mba));
341 * cio_commit_config - apply configuration to the subchannel
343 int cio_commit_config(struct subchannel *sch)
346 int ccode, retry, ret = 0;
348 if (stsch_err(sch->schid, &schib) || !css_sch_is_valid(&schib))
351 for (retry = 0; retry < 5; retry++) {
352 /* copy desired changes to local schib */
353 cio_apply_config(sch, &schib);
354 ccode = msch_err(sch->schid, &schib);
355 if (ccode < 0) /* -EIO if msch gets a program check. */
358 case 0: /* successful */
359 if (stsch_err(sch->schid, &schib) ||
360 !css_sch_is_valid(&schib))
362 if (cio_check_config(sch, &schib)) {
363 /* commit changes from local schib */
364 memcpy(&sch->schib, &schib, sizeof(schib));
369 case 1: /* status pending */
372 udelay(100); /* allow for recovery */
375 case 3: /* not operational */
383 * cio_update_schib - Perform stsch and update schib if subchannel is valid.
384 * @sch: subchannel on which to perform stsch
385 * Return zero on success, -ENODEV otherwise.
387 int cio_update_schib(struct subchannel *sch)
391 if (stsch_err(sch->schid, &schib) || !css_sch_is_valid(&schib))
394 memcpy(&sch->schib, &schib, sizeof(schib));
397 EXPORT_SYMBOL_GPL(cio_update_schib);
400 * cio_enable_subchannel - enable a subchannel.
401 * @sch: subchannel to be enabled
402 * @intparm: interruption parameter to set
404 int cio_enable_subchannel(struct subchannel *sch, u32 intparm)
409 CIO_TRACE_EVENT(2, "ensch");
410 CIO_TRACE_EVENT(2, dev_name(&sch->dev));
412 if (sch_is_pseudo_sch(sch))
414 if (cio_update_schib(sch))
418 sch->config.isc = sch->isc;
419 sch->config.intparm = intparm;
421 for (retry = 0; retry < 3; retry++) {
422 ret = cio_commit_config(sch);
425 * Got a program check in msch. Try without
426 * the concurrent sense bit the next time.
428 sch->config.csense = 0;
429 } else if (ret == -EBUSY) {
431 if (tsch(sch->schid, &irb) != 0)
436 CIO_HEX_EVENT(2, &ret, sizeof(ret));
439 EXPORT_SYMBOL_GPL(cio_enable_subchannel);
442 * cio_disable_subchannel - disable a subchannel.
443 * @sch: subchannel to disable
445 int cio_disable_subchannel(struct subchannel *sch)
450 CIO_TRACE_EVENT(2, "dissch");
451 CIO_TRACE_EVENT(2, dev_name(&sch->dev));
453 if (sch_is_pseudo_sch(sch))
455 if (cio_update_schib(sch))
460 for (retry = 0; retry < 3; retry++) {
461 ret = cio_commit_config(sch);
464 if (tsch(sch->schid, &irb) != 0)
469 CIO_HEX_EVENT(2, &ret, sizeof(ret));
472 EXPORT_SYMBOL_GPL(cio_disable_subchannel);
474 static int cio_check_devno_blacklisted(struct subchannel *sch)
476 if (is_blacklisted(sch->schid.ssid, sch->schib.pmcw.dev)) {
478 * This device must not be known to Linux. So we simply
479 * say that there is no device and return ENODEV.
481 CIO_MSG_EVENT(6, "Blacklisted device detected "
482 "at devno %04X, subchannel set %x\n",
483 sch->schib.pmcw.dev, sch->schid.ssid);
489 static int cio_validate_io_subchannel(struct subchannel *sch)
491 /* Initialization for io subchannels. */
492 if (!css_sch_is_valid(&sch->schib))
495 /* Devno is valid. */
496 return cio_check_devno_blacklisted(sch);
499 static int cio_validate_msg_subchannel(struct subchannel *sch)
501 /* Initialization for message subchannels. */
502 if (!css_sch_is_valid(&sch->schib))
505 /* Devno is valid. */
506 return cio_check_devno_blacklisted(sch);
510 * cio_validate_subchannel - basic validation of subchannel
511 * @sch: subchannel structure to be filled out
512 * @schid: subchannel id
514 * Find out subchannel type and initialize struct subchannel.
517 * -ENXIO for non-defined subchannels
518 * -ENODEV for invalid subchannels or blacklisted devices
519 * -EIO for subchannels in an invalid subchannel set
521 int cio_validate_subchannel(struct subchannel *sch, struct subchannel_id schid)
527 sprintf(dbf_txt, "valsch%x", schid.sch_no);
528 CIO_TRACE_EVENT(4, dbf_txt);
531 * The first subchannel that is not-operational (ccode==3)
532 * indicates that there aren't any more devices available.
533 * If stsch gets an exception, it means the current subchannel set
536 ccode = stsch_err(schid, &sch->schib);
538 err = (ccode == 3) ? -ENXIO : ccode;
541 sch->st = sch->schib.pmcw.st;
545 case SUBCHANNEL_TYPE_IO:
546 err = cio_validate_io_subchannel(sch);
548 case SUBCHANNEL_TYPE_MSG:
549 err = cio_validate_msg_subchannel(sch);
557 CIO_MSG_EVENT(4, "Subchannel 0.%x.%04x reports subchannel type %04X\n",
558 sch->schid.ssid, sch->schid.sch_no, sch->st);
564 * do_IRQ() handles all normal I/O device IRQ's (the special
565 * SMP cross-CPU interrupts have their own specific
569 void __irq_entry do_IRQ(struct pt_regs *regs)
571 struct tpi_info *tpi_info = (struct tpi_info *) ®s->int_code;
572 struct subchannel *sch;
574 struct pt_regs *old_regs;
576 old_regs = set_irq_regs(regs);
578 __this_cpu_write(s390_idle.nohz_delay, 1);
579 if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator)
580 /* Serve timer interrupts first. */
581 clock_comparator_work();
583 kstat_incr_irqs_this_cpu(IO_INTERRUPT, NULL);
584 irb = (struct irb *) &S390_lowcore.irb;
585 if (tpi_info->adapter_IO) {
586 do_adapter_IO(tpi_info->isc);
589 sch = (struct subchannel *)(unsigned long) tpi_info->intparm;
591 /* Clear pending interrupt condition. */
592 inc_irq_stat(IRQIO_CIO);
593 tsch(tpi_info->schid, irb);
596 spin_lock(sch->lock);
597 /* Store interrupt response block to lowcore. */
598 if (tsch(tpi_info->schid, irb) == 0) {
599 /* Keep subchannel information word up to date. */
600 memcpy (&sch->schib.scsw, &irb->scsw, sizeof (irb->scsw));
601 /* Call interrupt handler if there is one. */
602 if (sch->driver && sch->driver->irq)
603 sch->driver->irq(sch);
605 inc_irq_stat(IRQIO_CIO);
607 inc_irq_stat(IRQIO_CIO);
608 spin_unlock(sch->lock);
611 set_irq_regs(old_regs);
614 #ifdef CONFIG_CCW_CONSOLE
615 static struct subchannel *console_sch;
618 * Use cio_tsch to update the subchannel status and call the interrupt handler
619 * if status had been pending. Called with the subchannel's lock held.
621 void cio_tsch(struct subchannel *sch)
626 irb = (struct irb *)&S390_lowcore.irb;
627 /* Store interrupt response block to lowcore. */
628 if (tsch(sch->schid, irb) != 0)
629 /* Not status pending or not operational. */
631 memcpy(&sch->schib.scsw, &irb->scsw, sizeof(union scsw));
632 /* Call interrupt handler with updated status. */
633 irq_context = in_interrupt();
638 kstat_incr_irqs_this_cpu(IO_INTERRUPT, NULL);
639 if (sch->driver && sch->driver->irq)
640 sch->driver->irq(sch);
642 inc_irq_stat(IRQIO_CIO);
649 static int cio_test_for_console(struct subchannel_id schid, void *data)
653 if (stsch_err(schid, &schib) != 0)
655 if ((schib.pmcw.st == SUBCHANNEL_TYPE_IO) && schib.pmcw.dnv &&
656 (schib.pmcw.dev == console_devno)) {
657 console_irq = schid.sch_no;
658 return 1; /* found */
663 static int cio_get_console_sch_no(void)
665 struct subchannel_id schid;
668 init_subchannel_id(&schid);
669 if (console_irq != -1) {
670 /* VM provided us with the irq number of the console. */
671 schid.sch_no = console_irq;
672 if (stsch_err(schid, &schib) != 0 ||
673 (schib.pmcw.st != SUBCHANNEL_TYPE_IO) || !schib.pmcw.dnv)
675 console_devno = schib.pmcw.dev;
676 } else if (console_devno != -1) {
677 /* At least the console device number is known. */
678 for_each_subchannel(cio_test_for_console, NULL);
683 struct subchannel *cio_probe_console(void)
685 struct subchannel_id schid;
686 struct subchannel *sch;
689 sch_no = cio_get_console_sch_no();
691 pr_warning("No CCW console was found\n");
692 return ERR_PTR(-ENODEV);
694 init_subchannel_id(&schid);
695 schid.sch_no = sch_no;
696 sch = css_alloc_subchannel(schid);
700 isc_register(CONSOLE_ISC);
701 sch->config.isc = CONSOLE_ISC;
702 sch->config.intparm = (u32)(addr_t)sch;
703 ret = cio_commit_config(sch);
705 isc_unregister(CONSOLE_ISC);
706 put_device(&sch->dev);
713 int cio_is_console(struct subchannel_id schid)
717 return schid_equal(&schid, &console_sch->schid);
720 void cio_register_early_subchannels(void)
727 ret = css_register_subchannel(console_sch);
729 put_device(&console_sch->dev);
731 #endif /* CONFIG_CCW_CONSOLE */
734 __disable_subchannel_easy(struct subchannel_id schid, struct schib *schib)
739 for (retry=0;retry<3;retry++) {
741 cc = msch_err(schid, schib);
743 return (cc==3?-ENODEV:-EBUSY);
744 if (stsch_err(schid, schib) || !css_sch_is_valid(schib))
746 if (!schib->pmcw.ena)
749 return -EBUSY; /* uhm... */
753 __clear_io_subchannel_easy(struct subchannel_id schid)
759 for (retry=0;retry<20;retry++) {
763 tsch(ti.schid, (struct irb *)&S390_lowcore.irb);
764 if (schid_equal(&ti.schid, &schid))
772 static void __clear_chsc_subchannel_easy(void)
774 /* It seems we can only wait for a bit here :/ */
778 static int pgm_check_occured;
780 static void cio_reset_pgm_check_handler(void)
782 pgm_check_occured = 1;
785 static int stsch_reset(struct subchannel_id schid, struct schib *addr)
789 pgm_check_occured = 0;
790 s390_base_pgm_handler_fn = cio_reset_pgm_check_handler;
791 rc = stsch_err(schid, addr);
792 s390_base_pgm_handler_fn = NULL;
794 /* The program check handler could have changed pgm_check_occured. */
797 if (pgm_check_occured)
803 static int __shutdown_subchannel_easy(struct subchannel_id schid, void *data)
807 if (stsch_reset(schid, &schib))
811 switch(__disable_subchannel_easy(schid, &schib)) {
815 default: /* -EBUSY */
816 switch (schib.pmcw.st) {
817 case SUBCHANNEL_TYPE_IO:
818 if (__clear_io_subchannel_easy(schid))
819 goto out; /* give up... */
821 case SUBCHANNEL_TYPE_CHSC:
822 __clear_chsc_subchannel_easy();
825 /* No default clear strategy */
828 stsch_err(schid, &schib);
829 __disable_subchannel_easy(schid, &schib);
835 static atomic_t chpid_reset_count;
837 static void s390_reset_chpids_mcck_handler(void)
842 /* Check for pending channel report word. */
843 mci = (struct mci *)&S390_lowcore.mcck_interruption_code;
846 /* Process channel report words. */
847 while (stcrw(&crw) == 0) {
848 /* Check for responses to RCHP. */
849 if (crw.slct && crw.rsc == CRW_RSC_CPATH)
850 atomic_dec(&chpid_reset_count);
854 #define RCHP_TIMEOUT (30 * USEC_PER_SEC)
855 static void css_reset(void)
858 unsigned long long timeout;
861 /* Reset subchannels. */
862 for_each_subchannel(__shutdown_subchannel_easy, NULL);
863 /* Reset channel paths. */
864 s390_base_mcck_handler_fn = s390_reset_chpids_mcck_handler;
865 /* Enable channel report machine checks. */
866 __ctl_set_bit(14, 28);
867 /* Temporarily reenable machine checks. */
870 for (i = 0; i <= __MAX_CHPID; i++) {
873 if ((ret == 0) || (ret == 2))
875 * rchp either succeeded, or another rchp is already
876 * in progress. In either case, we'll get a crw.
878 atomic_inc(&chpid_reset_count);
880 /* Wait for machine check for all channel paths. */
881 timeout = get_tod_clock() + (RCHP_TIMEOUT << 12);
882 while (atomic_read(&chpid_reset_count) != 0) {
883 if (get_tod_clock() > timeout)
887 /* Disable machine checks again. */
888 local_mcck_disable();
889 /* Disable channel report machine checks. */
890 __ctl_clear_bit(14, 28);
891 s390_base_mcck_handler_fn = NULL;
894 static struct reset_call css_reset_call = {
898 static int __init init_css_reset_call(void)
900 atomic_set(&chpid_reset_count, 0);
901 register_reset_call(&css_reset_call);
905 arch_initcall(init_css_reset_call);
907 struct sch_match_id {
908 struct subchannel_id schid;
909 struct ccw_dev_id devid;
913 static int __reipl_subchannel_match(struct subchannel_id schid, void *data)
916 struct sch_match_id *match_id = data;
918 if (stsch_reset(schid, &schib))
920 if ((schib.pmcw.st == SUBCHANNEL_TYPE_IO) && schib.pmcw.dnv &&
921 (schib.pmcw.dev == match_id->devid.devno) &&
922 (schid.ssid == match_id->devid.ssid)) {
923 match_id->schid = schid;
930 static int reipl_find_schid(struct ccw_dev_id *devid,
931 struct subchannel_id *schid)
933 struct sch_match_id match_id;
935 match_id.devid = *devid;
936 match_id.rc = -ENODEV;
937 for_each_subchannel(__reipl_subchannel_match, &match_id);
938 if (match_id.rc == 0)
939 *schid = match_id.schid;
943 extern void do_reipl_asm(__u32 schid);
945 /* Make sure all subchannels are quiet before we re-ipl an lpar. */
946 void reipl_ccw_dev(struct ccw_dev_id *devid)
948 struct subchannel_id uninitialized_var(schid);
950 s390_reset_system(NULL, NULL);
951 if (reipl_find_schid(devid, &schid) != 0)
952 panic("IPL Device not found\n");
953 do_reipl_asm(*((__u32*)&schid));
956 int __init cio_get_iplinfo(struct cio_iplinfo *iplinfo)
958 struct subchannel_id schid;
961 schid = *(struct subchannel_id *)&S390_lowcore.subchannel_id;
964 if (stsch_err(schid, &schib))
966 if (schib.pmcw.st != SUBCHANNEL_TYPE_IO)
970 iplinfo->devno = schib.pmcw.dev;
971 iplinfo->is_qdio = schib.pmcw.qf;
976 * cio_tm_start_key - perform start function
977 * @sch: subchannel on which to perform the start function
978 * @tcw: transport-command word to be started
979 * @lpm: mask of paths to use
980 * @key: storage key to use for storage access
982 * Start the tcw on the given subchannel. Return zero on success, non-zero
985 int cio_tm_start_key(struct subchannel *sch, struct tcw *tcw, u8 lpm, u8 key)
988 union orb *orb = &to_io_private(sch)->orb;
990 memset(orb, 0, sizeof(union orb));
991 orb->tm.intparm = (u32) (addr_t) sch;
992 orb->tm.key = key >> 4;
994 orb->tm.lpm = lpm ? lpm : sch->lpm;
995 orb->tm.tcw = (u32) (addr_t) tcw;
996 cc = ssch(sch->schid, orb);
1004 return cio_start_handle_notoper(sch, lpm);
1009 * cio_tm_intrg - perform interrogate function
1010 * @sch - subchannel on which to perform the interrogate function
1012 * If the specified subchannel is running in transport-mode, perform the
1013 * interrogate function. Return zero on success, non-zero otherwie.
1015 int cio_tm_intrg(struct subchannel *sch)
1019 if (!to_io_private(sch)->orb.tm.b)
1021 cc = xsch(sch->schid);