css.c

/*
 *  drivers/s390/cio/css.c
 *  driver for channel subsystem
 *
 *    Copyright IBM Corp. 2002,2008
 *    Author(s): Arnd Bergmann (arndb@de.ibm.com)
 *		 Cornelia Huck (cornelia.huck@de.ibm.com)
 */
#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 <asm/isc.h>

#include "../s390mach.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;
static int need_reprobe = 0;
static int max_ssid = 0;

struct channel_subsystem *channel_subsystems[__MAX_CSSID + 1];

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;

	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;
}

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.set = idset_sch_new();
	if (!cb.set)
		return -ENOMEM;
	idset_fill(cb.set);
	cb.data = data;
	cb.fn_known_sch = fn_known;
	cb.fn_unknown_sch = fn_unknown;
	/* 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 struct subchannel *
css_alloc_subchannel(struct subchannel_id schid)
{
	struct subchannel *sch;
	int ret;

	sch = kmalloc (sizeof (*sch), GFP_KERNEL | GFP_DMA);
	if (sch == NULL)
		return ERR_PTR(-ENOMEM);
	ret = cio_validate_subchannel (sch, schid);
	if (ret < 0) {
		kfree(sch);
		return ERR_PTR(ret);
	}
	return sch;
}

static void
css_free_subchannel(struct subchannel *sch)
{
	if (sch) {
		/* Reset intparm to zeroes. */
		sch->schib.pmcw.intparm = 0;
		cio_modify(sch);
		kfree(sch->lock);
		kfree(sch);
	}
}

static void
css_subchannel_release(struct device *dev)
{
	struct subchannel *sch;

	sch = to_subchannel(dev);
	if (!cio_is_console(sch->schid)) {
		kfree(sch->lock);
		kfree(sch);
	}
}

static int css_sch_device_register(struct subchannel *sch)
{
	int ret;

	mutex_lock(&sch->reg_mutex);
	ret = device_register(&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);
	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;

	if (cio_is_console(sch->schid)) {
		/* Console is initialized too early for functions requiring
		 * memory allocation. */
		ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
	} else {
		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\n", 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\n", 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 struct attribute_group *default_subch_attr_groups[] = {
	&subch_attr_group,
	NULL,
};

static 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.release = &css_subchannel_release;
	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.
	 */
	sch->dev.uevent_suppress = 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\n",
			      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.
		 */
		sch->dev.uevent_suppress = 0;
		kobject_uevent(&sch->dev.kobj, KOBJ_ADD);
	}
	return ret;
}

int css_probe_device(struct subchannel_id schid)
{
	int ret;
	struct subchannel *sch;

	sch = css_alloc_subchannel(schid);
	if (IS_ERR(sch))
		return PTR_ERR(sch);
	ret = css_register_subchannel(sch);
	if (ret)
		css_free_subchannel(sch);
	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) || !css_sch_is_valid(&schib)) {
		/* Unusable - ignore. */
		return 0;
	}
	CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, unknown, "
			 "slow path.\n", schid.ssid, schid.sch_no, CIO_OPER);

	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.\n");
	}
	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);
}

static struct idset *slow_subchannel_set;
static spinlock_t slow_subchannel_lock;

static int __init slow_subchannel_init(void)
{
	spin_lock_init(&slow_subchannel_lock);
	slow_subchannel_set = idset_sch_new();
	if (!slow_subchannel_set) {
		CIO_MSG_EVENT(0, "could not allocate slow subchannel set\n");
		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 */
			break;
		default:
			rc = 0;
		}
	}
	return rc;
}

static void css_slow_path_func(struct work_struct *unused)
{
	CIO_TRACE_EVENT(4, "slowpath");
	for_each_subchannel_staged(slow_eval_known_fn, slow_eval_unknown_fn,
				   NULL);
}

static DECLARE_WORK(slow_path_work, css_slow_path_func);
struct workqueue_struct *slow_path_wq;

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);
	queue_work(slow_path_wq, &slow_path_work);
	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);
	queue_work(slow_path_wq, &slow_path_work);
	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
}

void css_wait_for_slow_path(void)
{
	flush_workqueue(ccw_device_notify_work);
	flush_workqueue(slow_path_wq);
}

/* Reprobe subchannel if unregistered. */
static int reprobe_subchannel(struct subchannel_id schid, void *data)
{
	int ret;

	CIO_MSG_EVENT(6, "cio: reprobe 0.%x.%04x\n",
		      schid.ssid, schid.sch_no);
	if (need_reprobe)
		return -EAGAIN;

	ret = css_probe_device(schid);
	switch (ret) {
	case 0:
		break;
	case -ENXIO:
	case -ENOMEM:
	case -EIO:
		/* These should abort looping */
		break;
	default:
		ret = 0;
	}

	return ret;
}

/* Work function used to reprobe all unregistered subchannels. */
static void reprobe_all(struct work_struct *unused)
{
	int ret;

	CIO_MSG_EVENT(4, "reprobe start\n");

	need_reprobe = 0;
	/* Make sure initial subchannel scan is done. */
	wait_event(ccw_device_init_wq,
		   atomic_read(&ccw_device_init_count) == 0);
	ret = for_each_subchannel_staged(NULL, reprobe_subchannel, NULL);

	CIO_MSG_EVENT(4, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
		      need_reprobe);
}

static DECLARE_WORK(css_reprobe_work, reprobe_all);

/* Schedule reprobing of all unregistered subchannels. */
void css_schedule_reprobe(void)
{
	need_reprobe = 1;
	queue_work(slow_path_wq, &css_reprobe_work);
}

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;

	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\n",
		      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\n",
			      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 >> 8) & 3;

	/*
	 * 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 int __init
__init_channel_subsystem(struct subchannel_id schid, void *data)
{
	struct subchannel *sch;
	int ret;

	if (cio_is_console(schid))
		sch = cio_get_console_subchannel();
	else {
		sch = css_alloc_subchannel(schid);
		if (IS_ERR(sch))
			ret = PTR_ERR(sch);
		else
			ret = 0;
		switch (ret) {
		case 0:
			break;
		case -ENOMEM:
			panic("Out of memory in init_channel_subsystem\n");
		/* -ENXIO: no more subchannels. */
		case -ENXIO:
			return ret;
		/* -EIO: this subchannel set not supported. */
		case -EIO:
			return ret;
		default:
			return 0;
		}
	}
	/*
	 * We register ALL valid subchannels in ioinfo, even those
	 * that have been present before init_channel_subsystem.
	 * These subchannels can't have been registered yet (kmalloc
	 * not working) so we do it now. This is true e.g. for the
	 * console subchannel.
	 */
	css_register_subchannel(sch);
	return 0;
}

static void __init
css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
{
	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 = hard_smp_processor_id();
#else
		css->global_pgid.pgid_high.cpu_addr = 0;
#endif
	}
	css->global_pgid.cpu_id = ((cpuid_t *) __LC_CPUID)->ident;
	css->global_pgid.cpu_model = ((cpuid_t *) __LC_CPUID)->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);
	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\n", 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 = strict_strtoul(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;
	sprintf(css->pseudo_subchannel->dev.bus_id, "defunct");
	ret = cio_create_sch_lock(css->pseudo_subchannel);
	if (ret) {
		kfree(css->pseudo_subchannel);
		return ret;
	}
	mutex_init(&css->mutex);
	css->valid = 1;
	css->cssid = nr;
	sprintf(css->device.bus_id, "css%x", nr);
	css->device.release = channel_subsystem_release;
	tod_high = (u32) (get_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,
};

/*
 * Now that the driver core is running, we can setup our channel subsystem.
 * The struct subchannel's are created during probing (except for the
 * static console subchannel).
 */
static int __init
init_channel_subsystem (void)
{
	int ret, i;

	ret = chsc_determine_css_characteristics();
	if (ret == -ENOMEM)
		goto out; /* No need to continue. */

	ret = chsc_alloc_sei_area();
	if (ret)
		goto out;

	ret = slow_subchannel_init();
	if (ret)
		goto out;

	ret = s390_register_crw_handler(CRW_RSC_SCH, css_process_crw);
	if (ret)
		goto out;

	if ((ret = bus_register(&css_bus_type)))
		goto out;

	/* Try to enable MSS. */
	ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
	switch (ret) {
	case 0: /* Success. */
		max_ssid = __MAX_SSID;
		break;
	case -ENOMEM:
		goto out_bus;
	default:
		max_ssid = 0;
	}
	/* 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)
			goto out_free;
		ret = device_register(&css->device);
		if (ret)
			goto out_free_all;
		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)
			goto out_file;
	}
	ret = register_reboot_notifier(&css_reboot_notifier);
	if (ret)
		goto out_pseudo;
	css_init_done = 1;

	/* Enable default isc for I/O subchannels. */
	isc_register(IO_SCH_ISC);

	for_each_subchannel(__init_channel_subsystem, NULL);
	return 0;
out_pseudo:
	device_unregister(&channel_subsystems[i]->pseudo_subchannel->dev);
out_file:
	device_remove_file(&channel_subsystems[i]->device,
			   &dev_attr_cm_enable);
out_device:
	device_unregister(&channel_subsystems[i]->device);
out_free_all:
	kfree(channel_subsystems[i]->pseudo_subchannel->lock);
	kfree(channel_subsystems[i]->pseudo_subchannel);
out_free:
	kfree(channel_subsystems[i]);
out_unregister:
	while (i > 0) {
		struct channel_subsystem *css;

		i--;
		css = channel_subsystems[i];
		device_unregister(&css->pseudo_subchannel->dev);
		if (css_chsc_characteristics.secm)
			device_remove_file(&css->device,
					   &dev_attr_cm_enable);
		device_unregister(&css->device);
	}
out_bus:
	bus_unregister(&css_bus_type);
out:
	s390_unregister_crw_handler(CRW_RSC_CSS);
	chsc_free_sei_area();
	kfree(slow_subchannel_set);
	printk(KERN_WARNING"cio: failed to initialize css driver (%d)!\n",
	       ret);
	return ret;
}

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;
}

struct bus_type css_bus_type = {
	.name     = "css",
	.match    = css_bus_match,
	.probe    = css_probe,
	.remove   = css_remove,
	.shutdown = css_shutdown,
	.uevent   = css_uevent,
};

/**
 * 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.name = cdrv->name;
	cdrv->drv.bus = &css_bus_type;
	cdrv->drv.owner = cdrv->owner;
	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);

subsys_initcall(init_channel_subsystem);

MODULE_LICENSE("GPL");
EXPORT_SYMBOL(css_bus_type);