/*
   * driver for channel subsystem
   *
   * Copyright IBM Corp. 2002, 2010
   *
   * Author(s): Arnd Bergmann (arndb@de.ibm.com)
   *	      Cornelia Huck (cornelia.huck@de.ibm.com)
   */
  
  #define KMSG_COMPONENT "cio"
  #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/device.h>
  #include <linux/slab.h>
  #include <linux/errno.h>
  #include <linux/list.h>
  #include <linux/reboot.h>
  #include <linux/suspend.h>
  #include <linux/proc_fs.h>
  #include <asm/isc.h>
  #include <asm/crw.h>
  
  #include "css.h"
  #include "cio.h"
  #include "cio_debug.h"
  #include "ioasm.h"
  #include "chsc.h"
  #include "device.h"
  #include "idset.h"
  #include "chp.h"
  
  int css_init_done = 0;
  int max_ssid;
  
  struct channel_subsystem *channel_subsystems[__MAX_CSSID + 1];
  static struct bus_type css_bus_type;
  
  int
  for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *data)
  {
  	struct subchannel_id schid;
  	int ret;
  
  	init_subchannel_id(&schid);
  	ret = -ENODEV;
  	do {
  		do {
  			ret = fn(schid, data);
  			if (ret)
  				break;
  		} while (schid.sch_no++ < __MAX_SUBCHANNEL);
  		schid.sch_no = 0;
  	} while (schid.ssid++ < max_ssid);
  	return ret;
  }
  
  struct cb_data {
  	void *data;
  	struct idset *set;
  	int (*fn_known_sch)(struct subchannel *, void *);
  	int (*fn_unknown_sch)(struct subchannel_id, void *);
  };
  
  static int call_fn_known_sch(struct device *dev, void *data)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct cb_data *cb = data;
  	int rc = 0;
  
  	if (cb->set)
  		idset_sch_del(cb->set, sch->schid);
  	if (cb->fn_known_sch)
  		rc = cb->fn_known_sch(sch, cb->data);
  	return rc;
  }
  
  static int call_fn_unknown_sch(struct subchannel_id schid, void *data)
  {
  	struct cb_data *cb = data;
  	int rc = 0;
  
  	if (idset_sch_contains(cb->set, schid))
  		rc = cb->fn_unknown_sch(schid, cb->data);
  	return rc;
  }
  
  static int call_fn_all_sch(struct subchannel_id schid, void *data)
  {
  	struct cb_data *cb = data;
  	struct subchannel *sch;
  	int rc = 0;
  
  	sch = get_subchannel_by_schid(schid);
  	if (sch) {
  		if (cb->fn_known_sch)
  			rc = cb->fn_known_sch(sch, cb->data);
  		put_device(&sch->dev);
  	} else {
  		if (cb->fn_unknown_sch)
  			rc = cb->fn_unknown_sch(schid, cb->data);
  	}
  
  	return rc;
  }
  
  int for_each_subchannel_staged(int (*fn_known)(struct subchannel *, void *),
  			       int (*fn_unknown)(struct subchannel_id,
  			       void *), void *data)
  {
  	struct cb_data cb;
  	int rc;
  
  	cb.data = data;
  	cb.fn_known_sch = fn_known;
  	cb.fn_unknown_sch = fn_unknown;
  
  	if (fn_known && !fn_unknown) {
  		/* Skip idset allocation in case of known-only loop. */
  		cb.set = NULL;
  		return bus_for_each_dev(&css_bus_type, NULL, &cb,
  					call_fn_known_sch);
  	}
  
  	cb.set = idset_sch_new();
  	if (!cb.set)
  		/* fall back to brute force scanning in case of oom */
  		return for_each_subchannel(call_fn_all_sch, &cb);
  
  	idset_fill(cb.set);
  
  	/* Process registered subchannels. */
  	rc = bus_for_each_dev(&css_bus_type, NULL, &cb, call_fn_known_sch);
  	if (rc)
  		goto out;
  	/* Process unregistered subchannels. */
  	if (fn_unknown)
  		rc = for_each_subchannel(call_fn_unknown_sch, &cb);
  out:
  	idset_free(cb.set);
  
  	return rc;
  }
  
  static void css_sch_todo(struct work_struct *work);
  
  static int css_sch_create_locks(struct subchannel *sch)
  {
  	sch->lock = kmalloc(sizeof(*sch->lock), GFP_KERNEL);
  	if (!sch->lock)
  		return -ENOMEM;
  
  	spin_lock_init(sch->lock);
  	mutex_init(&sch->reg_mutex);
  
  	return 0;
  }
  
  static void css_subchannel_release(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  
  	sch->config.intparm = 0;
  	cio_commit_config(sch);
  	kfree(sch->lock);
  	kfree(sch);
  }
  
  struct subchannel *css_alloc_subchannel(struct subchannel_id schid)
  {
  	struct subchannel *sch;
  	int ret;
  
  	sch = kzalloc(sizeof(*sch), GFP_KERNEL | GFP_DMA);
  	if (!sch)
  		return ERR_PTR(-ENOMEM);
  
  	ret = cio_validate_subchannel(sch, schid);
  	if (ret < 0)
  		goto err;
  
  	ret = css_sch_create_locks(sch);
  	if (ret)
  		goto err;
  
  	INIT_WORK(&sch->todo_work, css_sch_todo);
  	sch->dev.release = &css_subchannel_release;
  	device_initialize(&sch->dev);
  	return sch;
  
  err:
  	kfree(sch);
  	return ERR_PTR(ret);
  }
  
  static int css_sch_device_register(struct subchannel *sch)
  {
  	int ret;
  
  	mutex_lock(&sch->reg_mutex);
  	dev_set_name(&sch->dev, "0.%x.%04x", sch->schid.ssid,
  		     sch->schid.sch_no);
  	ret = device_add(&sch->dev);
  	mutex_unlock(&sch->reg_mutex);
  	return ret;
  }
  
  /**
   * css_sch_device_unregister - unregister a subchannel
   * @sch: subchannel to be unregistered
   */
  void css_sch_device_unregister(struct subchannel *sch)
  {
  	mutex_lock(&sch->reg_mutex);
  	if (device_is_registered(&sch->dev))
  		device_unregister(&sch->dev);
  	mutex_unlock(&sch->reg_mutex);
  }
  EXPORT_SYMBOL_GPL(css_sch_device_unregister);
  
  static void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
  {
  	int i;
  	int mask;
  
  	memset(ssd, 0, sizeof(struct chsc_ssd_info));
  	ssd->path_mask = pmcw->pim;
  	for (i = 0; i < 8; i++) {
  		mask = 0x80 >> i;
  		if (pmcw->pim & mask) {
  			chp_id_init(&ssd->chpid[i]);
  			ssd->chpid[i].id = pmcw->chpid[i];
  		}
  	}
  }
  
  static void ssd_register_chpids(struct chsc_ssd_info *ssd)
  {
  	int i;
  	int mask;
  
  	for (i = 0; i < 8; i++) {
  		mask = 0x80 >> i;
  		if (ssd->path_mask & mask)
  			if (!chp_is_registered(ssd->chpid[i]))
  				chp_new(ssd->chpid[i]);
  	}
  }
  
  void css_update_ssd_info(struct subchannel *sch)
  {
  	int ret;
  
  	ret = chsc_get_ssd_info(sch->schid, &sch->ssd_info);
  	if (ret)
  		ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
  
  	ssd_register_chpids(&sch->ssd_info);
  }
  
  static ssize_t type_show(struct device *dev, struct device_attribute *attr,
  			 char *buf)
  {
  	struct subchannel *sch = to_subchannel(dev);
  
  	return sprintf(buf, "%01x
  ", sch->st);
  }
  
  static DEVICE_ATTR(type, 0444, type_show, NULL);
  
  static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
  			     char *buf)
  {
  	struct subchannel *sch = to_subchannel(dev);
  
  	return sprintf(buf, "css:t%01X
  ", sch->st);
  }
  
  static DEVICE_ATTR(modalias, 0444, modalias_show, NULL);
  
  static struct attribute *subch_attrs[] = {
  	&dev_attr_type.attr,
  	&dev_attr_modalias.attr,
  	NULL,
  };
  
  static struct attribute_group subch_attr_group = {
  	.attrs = subch_attrs,
  };
  
  static const struct attribute_group *default_subch_attr_groups[] = {
  	&subch_attr_group,
  	NULL,
  };
  
  int css_register_subchannel(struct subchannel *sch)
  {
  	int ret;
  
  	/* Initialize the subchannel structure */
  	sch->dev.parent = &channel_subsystems[0]->device;
  	sch->dev.bus = &css_bus_type;
  	sch->dev.groups = default_subch_attr_groups;
  	/*
  	 * We don't want to generate uevents for I/O subchannels that don't
  	 * have a working ccw device behind them since they will be
  	 * unregistered before they can be used anyway, so we delay the add
  	 * uevent until after device recognition was successful.
  	 * Note that we suppress the uevent for all subchannel types;
  	 * the subchannel driver can decide itself when it wants to inform
  	 * userspace of its existence.
  	 */
  	dev_set_uevent_suppress(&sch->dev, 1);
  	css_update_ssd_info(sch);
  	/* make it known to the system */
  	ret = css_sch_device_register(sch);
  	if (ret) {
  		CIO_MSG_EVENT(0, "Could not register sch 0.%x.%04x: %d
  ",
  			      sch->schid.ssid, sch->schid.sch_no, ret);
  		return ret;
  	}
  	if (!sch->driver) {
  		/*
  		 * No driver matched. Generate the uevent now so that
  		 * a fitting driver module may be loaded based on the
  		 * modalias.
  		 */
  		dev_set_uevent_suppress(&sch->dev, 0);
  		kobject_uevent(&sch->dev.kobj, KOBJ_ADD);
  	}
  	return ret;
  }
  
  static int css_probe_device(struct subchannel_id schid)
  {
  	struct subchannel *sch;
  	int ret;
  
  	sch = css_alloc_subchannel(schid);
  	if (IS_ERR(sch))
  		return PTR_ERR(sch);
  
  	ret = css_register_subchannel(sch);
  	if (ret)
  		put_device(&sch->dev);
  
  	return ret;
  }
  
  static int
  check_subchannel(struct device * dev, void * data)
  {
  	struct subchannel *sch;
  	struct subchannel_id *schid = data;
  
  	sch = to_subchannel(dev);
  	return schid_equal(&sch->schid, schid);
  }
  
  struct subchannel *
  get_subchannel_by_schid(struct subchannel_id schid)
  {
  	struct device *dev;
  
  	dev = bus_find_device(&css_bus_type, NULL,
  			      &schid, check_subchannel);
  
  	return dev ? to_subchannel(dev) : NULL;
  }
  
  /**
   * css_sch_is_valid() - check if a subchannel is valid
   * @schib: subchannel information block for the subchannel
   */
  int css_sch_is_valid(struct schib *schib)
  {
  	if ((schib->pmcw.st == SUBCHANNEL_TYPE_IO) && !schib->pmcw.dnv)
  		return 0;
  	if ((schib->pmcw.st == SUBCHANNEL_TYPE_MSG) && !schib->pmcw.w)
  		return 0;
  	return 1;
  }
  EXPORT_SYMBOL_GPL(css_sch_is_valid);
  
  static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
  {
  	struct schib schib;
  
  	if (!slow) {
  		/* Will be done on the slow path. */
  		return -EAGAIN;
  	}
  	if (stsch_err(schid, &schib)) {
  		/* Subchannel is not provided. */
  		return -ENXIO;
  	}
  	if (!css_sch_is_valid(&schib)) {
  		/* Unusable - ignore. */
  		return 0;
  	}
  	CIO_MSG_EVENT(4, "event: sch 0.%x.%04x, new
  ", schid.ssid,
  		      schid.sch_no);
  
  	return css_probe_device(schid);
  }
  
  static int css_evaluate_known_subchannel(struct subchannel *sch, int slow)
  {
  	int ret = 0;
  
  	if (sch->driver) {
  		if (sch->driver->sch_event)
  			ret = sch->driver->sch_event(sch, slow);
  		else
  			dev_dbg(&sch->dev,
  				"Got subchannel machine check but "
  				"no sch_event handler provided.
  ");
  	}
  	if (ret != 0 && ret != -EAGAIN) {
  		CIO_MSG_EVENT(2, "eval: sch 0.%x.%04x, rc=%d
  ",
  			      sch->schid.ssid, sch->schid.sch_no, ret);
  	}
  	return ret;
  }
  
  static void css_evaluate_subchannel(struct subchannel_id schid, int slow)
  {
  	struct subchannel *sch;
  	int ret;
  
  	sch = get_subchannel_by_schid(schid);
  	if (sch) {
  		ret = css_evaluate_known_subchannel(sch, slow);
  		put_device(&sch->dev);
  	} else
  		ret = css_evaluate_new_subchannel(schid, slow);
  	if (ret == -EAGAIN)
  		css_schedule_eval(schid);
  }
  
  /**
   * css_sched_sch_todo - schedule a subchannel operation
   * @sch: subchannel
   * @todo: todo
   *
   * Schedule the operation identified by @todo to be performed on the slow path
   * workqueue. Do nothing if another operation with higher priority is already
   * scheduled. Needs to be called with subchannel lock held.
   */
  void css_sched_sch_todo(struct subchannel *sch, enum sch_todo todo)
  {
  	CIO_MSG_EVENT(4, "sch_todo: sched sch=0.%x.%04x todo=%d
  ",
  		      sch->schid.ssid, sch->schid.sch_no, todo);
  	if (sch->todo >= todo)
  		return;
  	/* Get workqueue ref. */
  	if (!get_device(&sch->dev))
  		return;
  	sch->todo = todo;
  	if (!queue_work(cio_work_q, &sch->todo_work)) {
  		/* Already queued, release workqueue ref. */
  		put_device(&sch->dev);
  	}
  }
  EXPORT_SYMBOL_GPL(css_sched_sch_todo);
  
  static void css_sch_todo(struct work_struct *work)
  {
  	struct subchannel *sch;
  	enum sch_todo todo;
  	int ret;
  
  	sch = container_of(work, struct subchannel, todo_work);
  	/* Find out todo. */
  	spin_lock_irq(sch->lock);
  	todo = sch->todo;
  	CIO_MSG_EVENT(4, "sch_todo: sch=0.%x.%04x, todo=%d
  ", sch->schid.ssid,
  		      sch->schid.sch_no, todo);
  	sch->todo = SCH_TODO_NOTHING;
  	spin_unlock_irq(sch->lock);
  	/* Perform todo. */
  	switch (todo) {
  	case SCH_TODO_NOTHING:
  		break;
  	case SCH_TODO_EVAL:
  		ret = css_evaluate_known_subchannel(sch, 1);
  		if (ret == -EAGAIN) {
  			spin_lock_irq(sch->lock);
  			css_sched_sch_todo(sch, todo);
  			spin_unlock_irq(sch->lock);
  		}
  		break;
  	case SCH_TODO_UNREG:
  		css_sch_device_unregister(sch);
  		break;
  	}
  	/* Release workqueue ref. */
  	put_device(&sch->dev);
  }
  
  static struct idset *slow_subchannel_set;
  static spinlock_t slow_subchannel_lock;
  static wait_queue_head_t css_eval_wq;
  static atomic_t css_eval_scheduled;
  
  static int __init slow_subchannel_init(void)
  {
  	spin_lock_init(&slow_subchannel_lock);
  	atomic_set(&css_eval_scheduled, 0);
  	init_waitqueue_head(&css_eval_wq);
  	slow_subchannel_set = idset_sch_new();
  	if (!slow_subchannel_set) {
  		CIO_MSG_EVENT(0, "could not allocate slow subchannel set
  ");
  		return -ENOMEM;
  	}
  	return 0;
  }
  
  static int slow_eval_known_fn(struct subchannel *sch, void *data)
  {
  	int eval;
  	int rc;
  
  	spin_lock_irq(&slow_subchannel_lock);
  	eval = idset_sch_contains(slow_subchannel_set, sch->schid);
  	idset_sch_del(slow_subchannel_set, sch->schid);
  	spin_unlock_irq(&slow_subchannel_lock);
  	if (eval) {
  		rc = css_evaluate_known_subchannel(sch, 1);
  		if (rc == -EAGAIN)
  			css_schedule_eval(sch->schid);
  	}
  	return 0;
  }
  
  static int slow_eval_unknown_fn(struct subchannel_id schid, void *data)
  {
  	int eval;
  	int rc = 0;
  
  	spin_lock_irq(&slow_subchannel_lock);
  	eval = idset_sch_contains(slow_subchannel_set, schid);
  	idset_sch_del(slow_subchannel_set, schid);
  	spin_unlock_irq(&slow_subchannel_lock);
  	if (eval) {
  		rc = css_evaluate_new_subchannel(schid, 1);
  		switch (rc) {
  		case -EAGAIN:
  			css_schedule_eval(schid);
  			rc = 0;
  			break;
  		case -ENXIO:
  		case -ENOMEM:
  		case -EIO:
  			/* These should abort looping */
  			spin_lock_irq(&slow_subchannel_lock);
  			idset_sch_del_subseq(slow_subchannel_set, schid);
  			spin_unlock_irq(&slow_subchannel_lock);
  			break;
  		default:
  			rc = 0;
  		}
  		/* Allow scheduling here since the containing loop might
  		 * take a while.  */
  		cond_resched();
  	}
  	return rc;
  }
  
  static void css_slow_path_func(struct work_struct *unused)
  {
  	unsigned long flags;
  
  	CIO_TRACE_EVENT(4, "slowpath");
  	for_each_subchannel_staged(slow_eval_known_fn, slow_eval_unknown_fn,
  				   NULL);
  	spin_lock_irqsave(&slow_subchannel_lock, flags);
  	if (idset_is_empty(slow_subchannel_set)) {
  		atomic_set(&css_eval_scheduled, 0);
  		wake_up(&css_eval_wq);
  	}
  	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
  }
  
  static DECLARE_DELAYED_WORK(slow_path_work, css_slow_path_func);
  struct workqueue_struct *cio_work_q;
  
  void css_schedule_eval(struct subchannel_id schid)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&slow_subchannel_lock, flags);
  	idset_sch_add(slow_subchannel_set, schid);
  	atomic_set(&css_eval_scheduled, 1);
  	queue_delayed_work(cio_work_q, &slow_path_work, 0);
  	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
  }
  
  void css_schedule_eval_all(void)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&slow_subchannel_lock, flags);
  	idset_fill(slow_subchannel_set);
  	atomic_set(&css_eval_scheduled, 1);
  	queue_delayed_work(cio_work_q, &slow_path_work, 0);
  	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
  }
  
  static int __unset_registered(struct device *dev, void *data)
  {
  	struct idset *set = data;
  	struct subchannel *sch = to_subchannel(dev);
  
  	idset_sch_del(set, sch->schid);
  	return 0;
  }
  
  void css_schedule_eval_all_unreg(unsigned long delay)
  {
  	unsigned long flags;
  	struct idset *unreg_set;
  
  	/* Find unregistered subchannels. */
  	unreg_set = idset_sch_new();
  	if (!unreg_set) {
  		/* Fallback. */
  		css_schedule_eval_all();
  		return;
  	}
  	idset_fill(unreg_set);
  	bus_for_each_dev(&css_bus_type, NULL, unreg_set, __unset_registered);
  	/* Apply to slow_subchannel_set. */
  	spin_lock_irqsave(&slow_subchannel_lock, flags);
  	idset_add_set(slow_subchannel_set, unreg_set);
  	atomic_set(&css_eval_scheduled, 1);
  	queue_delayed_work(cio_work_q, &slow_path_work, delay);
  	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
  	idset_free(unreg_set);
  }
  
  void css_wait_for_slow_path(void)
  {
  	flush_workqueue(cio_work_q);
  }
  
  /* Schedule reprobing of all unregistered subchannels. */
  void css_schedule_reprobe(void)
  {
  	/* Schedule with a delay to allow merging of subsequent calls. */
  	css_schedule_eval_all_unreg(1 * HZ);
  }
  EXPORT_SYMBOL_GPL(css_schedule_reprobe);
  
  /*
   * Called from the machine check handler for subchannel report words.
   */
  static void css_process_crw(struct crw *crw0, struct crw *crw1, int overflow)
  {
  	struct subchannel_id mchk_schid;
  	struct subchannel *sch;
  
  	if (overflow) {
  		css_schedule_eval_all();
  		return;
  	}
  	CIO_CRW_EVENT(2, "CRW0 reports slct=%d, oflw=%d, "
  		      "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X
  ",
  		      crw0->slct, crw0->oflw, crw0->chn, crw0->rsc, crw0->anc,
  		      crw0->erc, crw0->rsid);
  	if (crw1)
  		CIO_CRW_EVENT(2, "CRW1 reports slct=%d, oflw=%d, "
  			      "chn=%d, rsc=%X, anc=%d, erc=%X, rsid=%X
  ",
  			      crw1->slct, crw1->oflw, crw1->chn, crw1->rsc,
  			      crw1->anc, crw1->erc, crw1->rsid);
  	init_subchannel_id(&mchk_schid);
  	mchk_schid.sch_no = crw0->rsid;
  	if (crw1)
  		mchk_schid.ssid = (crw1->rsid >> 4) & 3;
  
  	if (crw0->erc == CRW_ERC_PMOD) {
  		sch = get_subchannel_by_schid(mchk_schid);
  		if (sch) {
  			css_update_ssd_info(sch);
  			put_device(&sch->dev);
  		}
  	}
  	/*
  	 * Since we are always presented with IPI in the CRW, we have to
  	 * use stsch() to find out if the subchannel in question has come
  	 * or gone.
  	 */
  	css_evaluate_subchannel(mchk_schid, 0);
  }
  
  static void __init
  css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
  {
  	struct cpuid cpu_id;
  
  	if (css_general_characteristics.mcss) {
  		css->global_pgid.pgid_high.ext_cssid.version = 0x80;
  		css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
  	} else {
  #ifdef CONFIG_SMP
  		css->global_pgid.pgid_high.cpu_addr = stap();
  #else
  		css->global_pgid.pgid_high.cpu_addr = 0;
  #endif
  	}
  	get_cpu_id(&cpu_id);
  	css->global_pgid.cpu_id = cpu_id.ident;
  	css->global_pgid.cpu_model = cpu_id.machine;
  	css->global_pgid.tod_high = tod_high;
  
  }
  
  static void
  channel_subsystem_release(struct device *dev)
  {
  	struct channel_subsystem *css;
  
  	css = to_css(dev);
  	mutex_destroy(&css->mutex);
  	if (css->pseudo_subchannel) {
  		/* Implies that it has been generated but never registered. */
  		css_subchannel_release(&css->pseudo_subchannel->dev);
  		css->pseudo_subchannel = NULL;
  	}
  	kfree(css);
  }
  
  static ssize_t
  css_cm_enable_show(struct device *dev, struct device_attribute *attr,
  		   char *buf)
  {
  	struct channel_subsystem *css = to_css(dev);
  	int ret;
  
  	if (!css)
  		return 0;
  	mutex_lock(&css->mutex);
  	ret = sprintf(buf, "%x
  ", css->cm_enabled);
  	mutex_unlock(&css->mutex);
  	return ret;
  }
  
  static ssize_t
  css_cm_enable_store(struct device *dev, struct device_attribute *attr,
  		    const char *buf, size_t count)
  {
  	struct channel_subsystem *css = to_css(dev);
  	int ret;
  	unsigned long val;
  
  	ret = kstrtoul(buf, 16, &val);
  	if (ret)
  		return ret;
  	mutex_lock(&css->mutex);
  	switch (val) {
  	case 0:
  		ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
  		break;
  	case 1:
  		ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
  		break;
  	default:
  		ret = -EINVAL;
  	}
  	mutex_unlock(&css->mutex);
  	return ret < 0 ? ret : count;
  }
  
  static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
  
  static int __init setup_css(int nr)
  {
  	u32 tod_high;
  	int ret;
  	struct channel_subsystem *css;
  
  	css = channel_subsystems[nr];
  	memset(css, 0, sizeof(struct channel_subsystem));
  	css->pseudo_subchannel =
  		kzalloc(sizeof(*css->pseudo_subchannel), GFP_KERNEL);
  	if (!css->pseudo_subchannel)
  		return -ENOMEM;
  	css->pseudo_subchannel->dev.parent = &css->device;
  	css->pseudo_subchannel->dev.release = css_subchannel_release;
  	dev_set_name(&css->pseudo_subchannel->dev, "defunct");
  	mutex_init(&css->pseudo_subchannel->reg_mutex);
  	ret = css_sch_create_locks(css->pseudo_subchannel);
  	if (ret) {
  		kfree(css->pseudo_subchannel);
  		return ret;
  	}
  	mutex_init(&css->mutex);
  	css->valid = 1;
  	css->cssid = nr;
  	dev_set_name(&css->device, "css%x", nr);
  	css->device.release = channel_subsystem_release;
  	tod_high = (u32) (get_tod_clock() >> 32);
  	css_generate_pgid(css, tod_high);
  	return 0;
  }
  
  static int css_reboot_event(struct notifier_block *this,
  			    unsigned long event,
  			    void *ptr)
  {
  	int ret, i;
  
  	ret = NOTIFY_DONE;
  	for (i = 0; i <= __MAX_CSSID; i++) {
  		struct channel_subsystem *css;
  
  		css = channel_subsystems[i];
  		mutex_lock(&css->mutex);
  		if (css->cm_enabled)
  			if (chsc_secm(css, 0))
  				ret = NOTIFY_BAD;
  		mutex_unlock(&css->mutex);
  	}
  
  	return ret;
  }
  
  static struct notifier_block css_reboot_notifier = {
  	.notifier_call = css_reboot_event,
  };
  
  /*
   * Since the css devices are neither on a bus nor have a class
   * nor have a special device type, we cannot stop/restart channel
   * path measurements via the normal suspend/resume callbacks, but have
   * to use notifiers.
   */
  static int css_power_event(struct notifier_block *this, unsigned long event,
  			   void *ptr)
  {
  	int ret, i;
  
  	switch (event) {
  	case PM_HIBERNATION_PREPARE:
  	case PM_SUSPEND_PREPARE:
  		ret = NOTIFY_DONE;
  		for (i = 0; i <= __MAX_CSSID; i++) {
  			struct channel_subsystem *css;
  
  			css = channel_subsystems[i];
  			mutex_lock(&css->mutex);
  			if (!css->cm_enabled) {
  				mutex_unlock(&css->mutex);
  				continue;
  			}
  			ret = __chsc_do_secm(css, 0);
  			ret = notifier_from_errno(ret);
  			mutex_unlock(&css->mutex);
  		}
  		break;
  	case PM_POST_HIBERNATION:
  	case PM_POST_SUSPEND:
  		ret = NOTIFY_DONE;
  		for (i = 0; i <= __MAX_CSSID; i++) {
  			struct channel_subsystem *css;
  
  			css = channel_subsystems[i];
  			mutex_lock(&css->mutex);
  			if (!css->cm_enabled) {
  				mutex_unlock(&css->mutex);
  				continue;
  			}
  			ret = __chsc_do_secm(css, 1);
  			ret = notifier_from_errno(ret);
  			mutex_unlock(&css->mutex);
  		}
  		/* search for subchannels, which appeared during hibernation */
  		css_schedule_reprobe();
  		break;
  	default:
  		ret = NOTIFY_DONE;
  	}
  	return ret;
  
  }
  static struct notifier_block css_power_notifier = {
  	.notifier_call = css_power_event,
  };
  
  /*
   * Now that the driver core is running, we can setup our channel subsystem.
   * The struct subchannel's are created during probing.
   */
  static int __init css_bus_init(void)
  {
  	int ret, i;
  
  	ret = chsc_init();
  	if (ret)
  		return ret;
  
  	chsc_determine_css_characteristics();
  	/* Try to enable MSS. */
  	ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
  	if (ret)
  		max_ssid = 0;
  	else /* Success. */
  		max_ssid = __MAX_SSID;
  
  	ret = slow_subchannel_init();
  	if (ret)
  		goto out;
  
  	ret = crw_register_handler(CRW_RSC_SCH, css_process_crw);
  	if (ret)
  		goto out;
  
  	if ((ret = bus_register(&css_bus_type)))
  		goto out;
  
  	/* Setup css structure. */
  	for (i = 0; i <= __MAX_CSSID; i++) {
  		struct channel_subsystem *css;
  
  		css = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
  		if (!css) {
  			ret = -ENOMEM;
  			goto out_unregister;
  		}
  		channel_subsystems[i] = css;
  		ret = setup_css(i);
  		if (ret) {
  			kfree(channel_subsystems[i]);
  			goto out_unregister;
  		}
  		ret = device_register(&css->device);
  		if (ret) {
  			put_device(&css->device);
  			goto out_unregister;
  		}
  		if (css_chsc_characteristics.secm) {
  			ret = device_create_file(&css->device,
  						 &dev_attr_cm_enable);
  			if (ret)
  				goto out_device;
  		}
  		ret = device_register(&css->pseudo_subchannel->dev);
  		if (ret) {
  			put_device(&css->pseudo_subchannel->dev);
  			goto out_file;
  		}
  	}
  	ret = register_reboot_notifier(&css_reboot_notifier);
  	if (ret)
  		goto out_unregister;
  	ret = register_pm_notifier(&css_power_notifier);
  	if (ret) {
  		unregister_reboot_notifier(&css_reboot_notifier);
  		goto out_unregister;
  	}
  	css_init_done = 1;
  
  	/* Enable default isc for I/O subchannels. */
  	isc_register(IO_SCH_ISC);
  
  	return 0;
  out_file:
  	if (css_chsc_characteristics.secm)
  		device_remove_file(&channel_subsystems[i]->device,
  				   &dev_attr_cm_enable);
  out_device:
  	device_unregister(&channel_subsystems[i]->device);
  out_unregister:
  	while (i > 0) {
  		struct channel_subsystem *css;
  
  		i--;
  		css = channel_subsystems[i];
  		device_unregister(&css->pseudo_subchannel->dev);
  		css->pseudo_subchannel = NULL;
  		if (css_chsc_characteristics.secm)
  			device_remove_file(&css->device,
  					   &dev_attr_cm_enable);
  		device_unregister(&css->device);
  	}
  	bus_unregister(&css_bus_type);
  out:
  	crw_unregister_handler(CRW_RSC_SCH);
  	idset_free(slow_subchannel_set);
  	chsc_init_cleanup();
  	pr_alert("The CSS device driver initialization failed with "
  		 "errno=%d
  ", ret);
  	return ret;
  }
  
  static void __init css_bus_cleanup(void)
  {
  	struct channel_subsystem *css;
  	int i;
  
  	for (i = 0; i <= __MAX_CSSID; i++) {
  		css = channel_subsystems[i];
  		device_unregister(&css->pseudo_subchannel->dev);
  		css->pseudo_subchannel = NULL;
  		if (css_chsc_characteristics.secm)
  			device_remove_file(&css->device, &dev_attr_cm_enable);
  		device_unregister(&css->device);
  	}
  	bus_unregister(&css_bus_type);
  	crw_unregister_handler(CRW_RSC_SCH);
  	idset_free(slow_subchannel_set);
  	chsc_init_cleanup();
  	isc_unregister(IO_SCH_ISC);
  }
  
  static int __init channel_subsystem_init(void)
  {
  	int ret;
  
  	ret = css_bus_init();
  	if (ret)
  		return ret;
  	cio_work_q = create_singlethread_workqueue("cio");
  	if (!cio_work_q) {
  		ret = -ENOMEM;
  		goto out_bus;
  	}
  	ret = io_subchannel_init();
  	if (ret)
  		goto out_wq;
  
  	return ret;
  out_wq:
  	destroy_workqueue(cio_work_q);
  out_bus:
  	css_bus_cleanup();
  	return ret;
  }
  subsys_initcall(channel_subsystem_init);
  
  static int css_settle(struct device_driver *drv, void *unused)
  {
  	struct css_driver *cssdrv = to_cssdriver(drv);
  
  	if (cssdrv->settle)
  		return cssdrv->settle();
  	return 0;
  }
  
  int css_complete_work(void)
  {
  	int ret;
  
  	/* Wait for the evaluation of subchannels to finish. */
  	ret = wait_event_interruptible(css_eval_wq,
  				       atomic_read(&css_eval_scheduled) == 0);
  	if (ret)
  		return -EINTR;
  	flush_workqueue(cio_work_q);
  	/* Wait for the subchannel type specific initialization to finish */
  	return bus_for_each_drv(&css_bus_type, NULL, NULL, css_settle);
  }
  
  
  /*
   * Wait for the initialization of devices to finish, to make sure we are
   * done with our setup if the search for the root device starts.
   */
  static int __init channel_subsystem_init_sync(void)
  {
  	/* Register subchannels which are already in use. */
  	cio_register_early_subchannels();
  	/* Start initial subchannel evaluation. */
  	css_schedule_eval_all();
  	css_complete_work();
  	return 0;
  }
  subsys_initcall_sync(channel_subsystem_init_sync);
  
  void channel_subsystem_reinit(void)
  {
  	struct channel_path *chp;
  	struct chp_id chpid;
  
  	chsc_enable_facility(CHSC_SDA_OC_MSS);
  	chp_id_for_each(&chpid) {
  		chp = chpid_to_chp(chpid);
  		if (chp)
  			chp_update_desc(chp);
  	}
  }
  
  #ifdef CONFIG_PROC_FS
  static ssize_t cio_settle_write(struct file *file, const char __user *buf,
  				size_t count, loff_t *ppos)
  {
  	int ret;
  
  	/* Handle pending CRW's. */
  	crw_wait_for_channel_report();
  	ret = css_complete_work();
  
  	return ret ? ret : count;
  }
  
  static const struct file_operations cio_settle_proc_fops = {
  	.open = nonseekable_open,
  	.write = cio_settle_write,
  	.llseek = no_llseek,
  };
  
  static int __init cio_settle_init(void)
  {
  	struct proc_dir_entry *entry;
  
  	entry = proc_create("cio_settle", S_IWUSR, NULL,
  			    &cio_settle_proc_fops);
  	if (!entry)
  		return -ENOMEM;
  	return 0;
  }
  device_initcall(cio_settle_init);
  #endif /*CONFIG_PROC_FS*/
  
  int sch_is_pseudo_sch(struct subchannel *sch)
  {
  	return sch == to_css(sch->dev.parent)->pseudo_subchannel;
  }
  
  static int css_bus_match(struct device *dev, struct device_driver *drv)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *driver = to_cssdriver(drv);
  	struct css_device_id *id;
  
  	for (id = driver->subchannel_type; id->match_flags; id++) {
  		if (sch->st == id->type)
  			return 1;
  	}
  
  	return 0;
  }
  
  static int css_probe(struct device *dev)
  {
  	struct subchannel *sch;
  	int ret;
  
  	sch = to_subchannel(dev);
  	sch->driver = to_cssdriver(dev->driver);
  	ret = sch->driver->probe ? sch->driver->probe(sch) : 0;
  	if (ret)
  		sch->driver = NULL;
  	return ret;
  }
  
  static int css_remove(struct device *dev)
  {
  	struct subchannel *sch;
  	int ret;
  
  	sch = to_subchannel(dev);
  	ret = sch->driver->remove ? sch->driver->remove(sch) : 0;
  	sch->driver = NULL;
  	return ret;
  }
  
  static void css_shutdown(struct device *dev)
  {
  	struct subchannel *sch;
  
  	sch = to_subchannel(dev);
  	if (sch->driver && sch->driver->shutdown)
  		sch->driver->shutdown(sch);
  }
  
  static int css_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	int ret;
  
  	ret = add_uevent_var(env, "ST=%01X", sch->st);
  	if (ret)
  		return ret;
  	ret = add_uevent_var(env, "MODALIAS=css:t%01X", sch->st);
  	return ret;
  }
  
  static int css_pm_prepare(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *drv;
  
  	if (mutex_is_locked(&sch->reg_mutex))
  		return -EAGAIN;
  	if (!sch->dev.driver)
  		return 0;
  	drv = to_cssdriver(sch->dev.driver);
  	/* Notify drivers that they may not register children. */
  	return drv->prepare ? drv->prepare(sch) : 0;
  }
  
  static void css_pm_complete(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *drv;
  
  	if (!sch->dev.driver)
  		return;
  	drv = to_cssdriver(sch->dev.driver);
  	if (drv->complete)
  		drv->complete(sch);
  }
  
  static int css_pm_freeze(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *drv;
  
  	if (!sch->dev.driver)
  		return 0;
  	drv = to_cssdriver(sch->dev.driver);
  	return drv->freeze ? drv->freeze(sch) : 0;
  }
  
  static int css_pm_thaw(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *drv;
  
  	if (!sch->dev.driver)
  		return 0;
  	drv = to_cssdriver(sch->dev.driver);
  	return drv->thaw ? drv->thaw(sch) : 0;
  }
  
  static int css_pm_restore(struct device *dev)
  {
  	struct subchannel *sch = to_subchannel(dev);
  	struct css_driver *drv;
  
  	css_update_ssd_info(sch);
  	if (!sch->dev.driver)
  		return 0;
  	drv = to_cssdriver(sch->dev.driver);
  	return drv->restore ? drv->restore(sch) : 0;
  }
  
  static const struct dev_pm_ops css_pm_ops = {
  	.prepare = css_pm_prepare,
  	.complete = css_pm_complete,
  	.freeze = css_pm_freeze,
  	.thaw = css_pm_thaw,
  	.restore = css_pm_restore,
  };
  
  static struct bus_type css_bus_type = {
  	.name     = "css",
  	.match    = css_bus_match,
  	.probe    = css_probe,
  	.remove   = css_remove,
  	.shutdown = css_shutdown,
  	.uevent   = css_uevent,
  	.pm = &css_pm_ops,
  };
  
  /**
   * css_driver_register - register a css driver
   * @cdrv: css driver to register
   *
   * This is mainly a wrapper around driver_register that sets name
   * and bus_type in the embedded struct device_driver correctly.
   */
  int css_driver_register(struct css_driver *cdrv)
  {
  	cdrv->drv.bus = &css_bus_type;
  	return driver_register(&cdrv->drv);
  }
  EXPORT_SYMBOL_GPL(css_driver_register);
  
  /**
   * css_driver_unregister - unregister a css driver
   * @cdrv: css driver to unregister
   *
   * This is a wrapper around driver_unregister.
   */
  void css_driver_unregister(struct css_driver *cdrv)
  {
  	driver_unregister(&cdrv->drv);
  }
  EXPORT_SYMBOL_GPL(css_driver_unregister);
  
  MODULE_LICENSE("GPL");