Merge master.kernel.org:/pub/scm/linux/kernel/git/paulus/powerpc

[deliverable/linux.git] / drivers / s390 / cio / device.c

/*
 *  drivers/s390/cio/device.c
 *  bus driver for ccw devices
 *
 *    Copyright (C) 2002 IBM Deutschland Entwicklung GmbH,
 *                       IBM Corporation
 *    Author(s): Arnd Bergmann (arndb@de.ibm.com)
 *               Cornelia Huck (cornelia.huck@de.ibm.com)
 *               Martin Schwidefsky (schwidefsky@de.ibm.com)
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/device.h>
#include <linux/workqueue.h>

#include <asm/ccwdev.h>
#include <asm/cio.h>
#include <asm/param.h>          /* HZ */

#include "cio.h"
#include "css.h"
#include "device.h"
#include "ioasm.h"

/******************* bus type handling ***********************/

/* The Linux driver model distinguishes between a bus type and
 * the bus itself. Of course we only have one channel
 * subsystem driver and one channel system per machine, but
 * we still use the abstraction. T.R. says it's a good idea. */
static int
ccw_bus_match (struct device * dev, struct device_driver * drv)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_driver *cdrv = to_ccwdrv(drv);
        const struct ccw_device_id *ids = cdrv->ids, *found;

        if (!ids)
                return 0;

        found = ccw_device_id_match(ids, &cdev->id);
        if (!found)
                return 0;

        cdev->id.driver_info = found->driver_info;

        return 1;
}

/* Store modalias string delimited by prefix/suffix string into buffer with
 * specified size. Return length of resulting string (excluding trailing '\0')
 * even if string doesn't fit buffer (snprintf semantics). */
static int snprint_alias(char *buf, size_t size, const char *prefix,
                         struct ccw_device_id *id, const char *suffix)
{
        int len;

        len = snprintf(buf, size, "%sccw:t%04Xm%02X", prefix, id->cu_type,
                       id->cu_model);
        if (len > size)
                return len;
        buf += len;
        size -= len;

        if (id->dev_type != 0)
                len += snprintf(buf, size, "dt%04Xdm%02X%s", id->dev_type,
                                id->dev_model, suffix);
        else
                len += snprintf(buf, size, "dtdm%s", suffix);

        return len;
}

/* Set up environment variables for ccw device uevent. Return 0 on success,
 * non-zero otherwise. */
static int ccw_uevent(struct device *dev, char **envp, int num_envp,
                      char *buffer, int buffer_size)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_device_id *id = &(cdev->id);
        int i = 0;
        int len;

        /* CU_TYPE= */
        len = snprintf(buffer, buffer_size, "CU_TYPE=%04X", id->cu_type) + 1;
        if (len > buffer_size || i >= num_envp)
                return -ENOMEM;
        envp[i++] = buffer;
        buffer += len;
        buffer_size -= len;

        /* CU_MODEL= */
        len = snprintf(buffer, buffer_size, "CU_MODEL=%02X", id->cu_model) + 1;
        if (len > buffer_size || i >= num_envp)
                return -ENOMEM;
        envp[i++] = buffer;
        buffer += len;
        buffer_size -= len;

        /* The next two can be zero, that's ok for us */
        /* DEV_TYPE= */
        len = snprintf(buffer, buffer_size, "DEV_TYPE=%04X", id->dev_type) + 1;
        if (len > buffer_size || i >= num_envp)
                return -ENOMEM;
        envp[i++] = buffer;
        buffer += len;
        buffer_size -= len;

        /* DEV_MODEL= */
        len = snprintf(buffer, buffer_size, "DEV_MODEL=%02X",
                        (unsigned char) id->dev_model) + 1;
        if (len > buffer_size || i >= num_envp)
                return -ENOMEM;
        envp[i++] = buffer;
        buffer += len;
        buffer_size -= len;

        /* MODALIAS=  */
        len = snprint_alias(buffer, buffer_size, "MODALIAS=", id, "") + 1;
        if (len > buffer_size || i >= num_envp)
                return -ENOMEM;
        envp[i++] = buffer;
        buffer += len;
        buffer_size -= len;

        envp[i] = NULL;

        return 0;
}

struct bus_type ccw_bus_type;

static int io_subchannel_probe (struct subchannel *);
static int io_subchannel_remove (struct subchannel *);
void io_subchannel_irq (struct device *);
static int io_subchannel_notify(struct device *, int);
static void io_subchannel_verify(struct device *);
static void io_subchannel_ioterm(struct device *);
static void io_subchannel_shutdown(struct subchannel *);

struct css_driver io_subchannel_driver = {
        .subchannel_type = SUBCHANNEL_TYPE_IO,
        .drv = {
                .name = "io_subchannel",
                .bus  = &css_bus_type,
        },
        .irq = io_subchannel_irq,
        .notify = io_subchannel_notify,
        .verify = io_subchannel_verify,
        .termination = io_subchannel_ioterm,
        .probe = io_subchannel_probe,
        .remove = io_subchannel_remove,
        .shutdown = io_subchannel_shutdown,
};

struct workqueue_struct *ccw_device_work;
struct workqueue_struct *ccw_device_notify_work;
wait_queue_head_t ccw_device_init_wq;
atomic_t ccw_device_init_count;

static int __init
init_ccw_bus_type (void)
{
        int ret;

        init_waitqueue_head(&ccw_device_init_wq);
        atomic_set(&ccw_device_init_count, 0);

        ccw_device_work = create_singlethread_workqueue("cio");
        if (!ccw_device_work)
                return -ENOMEM; /* FIXME: better errno ? */
        ccw_device_notify_work = create_singlethread_workqueue("cio_notify");
        if (!ccw_device_notify_work) {
                ret = -ENOMEM; /* FIXME: better errno ? */
                goto out_err;
        }
        slow_path_wq = create_singlethread_workqueue("kslowcrw");
        if (!slow_path_wq) {
                ret = -ENOMEM; /* FIXME: better errno ? */
                goto out_err;
        }
        if ((ret = bus_register (&ccw_bus_type)))
                goto out_err;

        if ((ret = driver_register(&io_subchannel_driver.drv)))
                goto out_err;

        wait_event(ccw_device_init_wq,
                   atomic_read(&ccw_device_init_count) == 0);
        flush_workqueue(ccw_device_work);
        return 0;
out_err:
        if (ccw_device_work)
                destroy_workqueue(ccw_device_work);
        if (ccw_device_notify_work)
                destroy_workqueue(ccw_device_notify_work);
        if (slow_path_wq)
                destroy_workqueue(slow_path_wq);
        return ret;
}

static void __exit
cleanup_ccw_bus_type (void)
{
        driver_unregister(&io_subchannel_driver.drv);
        bus_unregister(&ccw_bus_type);
        destroy_workqueue(ccw_device_notify_work);
        destroy_workqueue(ccw_device_work);
}

subsys_initcall(init_ccw_bus_type);
module_exit(cleanup_ccw_bus_type);

/************************ device handling **************************/

/*
 * A ccw_device has some interfaces in sysfs in addition to the
 * standard ones.
 * The following entries are designed to export the information which
 * resided in 2.4 in /proc/subchannels. Subchannel and device number
 * are obvious, so they don't have an entry :)
 * TODO: Split chpids and pimpampom up? Where is "in use" in the tree?
 */
static ssize_t
chpids_show (struct device * dev, struct device_attribute *attr, char * buf)
{
        struct subchannel *sch = to_subchannel(dev);
        struct ssd_info *ssd = &sch->ssd_info;
        ssize_t ret = 0;
        int chp;

        for (chp = 0; chp < 8; chp++)
                ret += sprintf (buf+ret, "%02x ", ssd->chpid[chp]);

        ret += sprintf (buf+ret, "\n");
        return min((ssize_t)PAGE_SIZE, ret);
}

static ssize_t
pimpampom_show (struct device * dev, struct device_attribute *attr, char * buf)
{
        struct subchannel *sch = to_subchannel(dev);
        struct pmcw *pmcw = &sch->schib.pmcw;

        return sprintf (buf, "%02x %02x %02x\n",
                        pmcw->pim, pmcw->pam, pmcw->pom);
}

static ssize_t
devtype_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_device_id *id = &(cdev->id);

        if (id->dev_type != 0)
                return sprintf(buf, "%04x/%02x\n",
                                id->dev_type, id->dev_model);
        else
                return sprintf(buf, "n/a\n");
}

static ssize_t
cutype_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_device_id *id = &(cdev->id);

        return sprintf(buf, "%04x/%02x\n",
                       id->cu_type, id->cu_model);
}

static ssize_t
modalias_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_device_id *id = &(cdev->id);
        int len;

        len = snprint_alias(buf, PAGE_SIZE, "", id, "\n") + 1;

        return len > PAGE_SIZE ? PAGE_SIZE : len;
}

static ssize_t
online_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        struct ccw_device *cdev = to_ccwdev(dev);

        return sprintf(buf, cdev->online ? "1\n" : "0\n");
}

static void
ccw_device_remove_disconnected(struct ccw_device *cdev)
{
        struct subchannel *sch;
        /*
         * Forced offline in disconnected state means
         * 'throw away device'.
         */
        sch = to_subchannel(cdev->dev.parent);
        css_sch_device_unregister(sch);
        /* Reset intparm to zeroes. */
        sch->schib.pmcw.intparm = 0;
        cio_modify(sch);
        put_device(&sch->dev);
}

int
ccw_device_set_offline(struct ccw_device *cdev)
{
        int ret;

        if (!cdev)
                return -ENODEV;
        if (!cdev->online || !cdev->drv)
                return -EINVAL;

        if (cdev->drv->set_offline) {
                ret = cdev->drv->set_offline(cdev);
                if (ret != 0)
                        return ret;
        }
        cdev->online = 0;
        spin_lock_irq(cdev->ccwlock);
        ret = ccw_device_offline(cdev);
        if (ret == -ENODEV) {
                if (cdev->private->state != DEV_STATE_NOT_OPER) {
                        cdev->private->state = DEV_STATE_OFFLINE;
                        dev_fsm_event(cdev, DEV_EVENT_NOTOPER);
                }
                spin_unlock_irq(cdev->ccwlock);
                return ret;
        }
        spin_unlock_irq(cdev->ccwlock);
        if (ret == 0)
                wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
        else {
                pr_debug("ccw_device_offline returned %d, device %s\n",
                         ret, cdev->dev.bus_id);
                cdev->online = 1;
        }
        return ret;
}

int
ccw_device_set_online(struct ccw_device *cdev)
{
        int ret;

        if (!cdev)
                return -ENODEV;
        if (cdev->online || !cdev->drv)
                return -EINVAL;

        spin_lock_irq(cdev->ccwlock);
        ret = ccw_device_online(cdev);
        spin_unlock_irq(cdev->ccwlock);
        if (ret == 0)
                wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
        else {
                pr_debug("ccw_device_online returned %d, device %s\n",
                         ret, cdev->dev.bus_id);
                return ret;
        }
        if (cdev->private->state != DEV_STATE_ONLINE)
                return -ENODEV;
        if (!cdev->drv->set_online || cdev->drv->set_online(cdev) == 0) {
                cdev->online = 1;
                return 0;
        }
        spin_lock_irq(cdev->ccwlock);
        ret = ccw_device_offline(cdev);
        spin_unlock_irq(cdev->ccwlock);
        if (ret == 0)
                wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
        else 
                pr_debug("ccw_device_offline returned %d, device %s\n",
                         ret, cdev->dev.bus_id);
        return (ret == 0) ? -ENODEV : ret;
}

static ssize_t
online_store (struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        int i, force, ret;
        char *tmp;

        if (atomic_cmpxchg(&cdev->private->onoff, 0, 1) != 0)
                return -EAGAIN;

        if (cdev->drv && !try_module_get(cdev->drv->owner)) {
                atomic_set(&cdev->private->onoff, 0);
                return -EINVAL;
        }
        if (!strncmp(buf, "force\n", count)) {
                force = 1;
                i = 1;
        } else {
                force = 0;
                i = simple_strtoul(buf, &tmp, 16);
        }
        if (i == 1) {
                /* Do device recognition, if needed. */
                if (cdev->id.cu_type == 0) {
                        ret = ccw_device_recognition(cdev);
                        if (ret) {
                                printk(KERN_WARNING"Couldn't start recognition "
                                       "for device %s (ret=%d)\n",
                                       cdev->dev.bus_id, ret);
                                goto out;
                        }
                        wait_event(cdev->private->wait_q,
                                   cdev->private->flags.recog_done);
                }
                if (cdev->drv && cdev->drv->set_online)
                        ccw_device_set_online(cdev);
        } else if (i == 0) {
                if (cdev->private->state == DEV_STATE_DISCONNECTED)
                        ccw_device_remove_disconnected(cdev);
                else if (cdev->drv && cdev->drv->set_offline)
                        ccw_device_set_offline(cdev);
        }
        if (force && cdev->private->state == DEV_STATE_BOXED) {
                ret = ccw_device_stlck(cdev);
                if (ret) {
                        printk(KERN_WARNING"ccw_device_stlck for device %s "
                               "returned %d!\n", cdev->dev.bus_id, ret);
                        goto out;
                }
                /* Do device recognition, if needed. */
                if (cdev->id.cu_type == 0) {
                        cdev->private->state = DEV_STATE_NOT_OPER;
                        ret = ccw_device_recognition(cdev);
                        if (ret) {
                                printk(KERN_WARNING"Couldn't start recognition "
                                       "for device %s (ret=%d)\n",
                                       cdev->dev.bus_id, ret);
                                goto out;
                        }
                        wait_event(cdev->private->wait_q,
                                   cdev->private->flags.recog_done);
                }
                if (cdev->drv && cdev->drv->set_online)
                        ccw_device_set_online(cdev);
        }
        out:
        if (cdev->drv)
                module_put(cdev->drv->owner);
        atomic_set(&cdev->private->onoff, 0);
        return count;
}

static ssize_t
available_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct subchannel *sch;

        switch (cdev->private->state) {
        case DEV_STATE_BOXED:
                return sprintf(buf, "boxed\n");
        case DEV_STATE_DISCONNECTED:
        case DEV_STATE_DISCONNECTED_SENSE_ID:
        case DEV_STATE_NOT_OPER:
                sch = to_subchannel(dev->parent);
                if (!sch->lpm)
                        return sprintf(buf, "no path\n");
                else
                        return sprintf(buf, "no device\n");
        default:
                /* All other states considered fine. */
                return sprintf(buf, "good\n");
        }
}

static DEVICE_ATTR(chpids, 0444, chpids_show, NULL);
static DEVICE_ATTR(pimpampom, 0444, pimpampom_show, NULL);
static DEVICE_ATTR(devtype, 0444, devtype_show, NULL);
static DEVICE_ATTR(cutype, 0444, cutype_show, NULL);
static DEVICE_ATTR(modalias, 0444, modalias_show, NULL);
static DEVICE_ATTR(online, 0644, online_show, online_store);
extern struct device_attribute dev_attr_cmb_enable;
static DEVICE_ATTR(availability, 0444, available_show, NULL);

static struct attribute * subch_attrs[] = {
        &dev_attr_chpids.attr,
        &dev_attr_pimpampom.attr,
        NULL,
};

static struct attribute_group subch_attr_group = {
        .attrs = subch_attrs,
};

static inline int
subchannel_add_files (struct device *dev)
{
        return sysfs_create_group(&dev->kobj, &subch_attr_group);
}

static struct attribute * ccwdev_attrs[] = {
        &dev_attr_devtype.attr,
        &dev_attr_cutype.attr,
        &dev_attr_modalias.attr,
        &dev_attr_online.attr,
        &dev_attr_cmb_enable.attr,
        &dev_attr_availability.attr,
        NULL,
};

static struct attribute_group ccwdev_attr_group = {
        .attrs = ccwdev_attrs,
};

static inline int
device_add_files (struct device *dev)
{
        return sysfs_create_group(&dev->kobj, &ccwdev_attr_group);
}

static inline void
device_remove_files(struct device *dev)
{
        sysfs_remove_group(&dev->kobj, &ccwdev_attr_group);
}

/* this is a simple abstraction for device_register that sets the
 * correct bus type and adds the bus specific files */
static int ccw_device_register(struct ccw_device *cdev)
{
        struct device *dev = &cdev->dev;
        int ret;

        dev->bus = &ccw_bus_type;

        if ((ret = device_add(dev)))
                return ret;

        set_bit(1, &cdev->private->registered);
        if ((ret = device_add_files(dev))) {
                if (test_and_clear_bit(1, &cdev->private->registered))
                        device_del(dev);
        }
        return ret;
}

struct match_data {
        struct ccw_dev_id dev_id;
        struct ccw_device * sibling;
};

static int
match_devno(struct device * dev, void * data)
{
        struct match_data * d = data;
        struct ccw_device * cdev;

        cdev = to_ccwdev(dev);
        if ((cdev->private->state == DEV_STATE_DISCONNECTED) &&
            ccw_dev_id_is_equal(&cdev->private->dev_id, &d->dev_id) &&
            (cdev != d->sibling)) {
                cdev->private->state = DEV_STATE_NOT_OPER;
                return 1;
        }
        return 0;
}

static struct ccw_device * get_disc_ccwdev_by_dev_id(struct ccw_dev_id *dev_id,
                                                     struct ccw_device *sibling)
{
        struct device *dev;
        struct match_data data;

        data.dev_id = *dev_id;
        data.sibling = sibling;
        dev = bus_find_device(&ccw_bus_type, NULL, &data, match_devno);

        return dev ? to_ccwdev(dev) : NULL;
}

static void
ccw_device_add_changed(void *data)
{

        struct ccw_device *cdev;

        cdev = data;
        if (device_add(&cdev->dev)) {
                put_device(&cdev->dev);
                return;
        }
        set_bit(1, &cdev->private->registered);
        if (device_add_files(&cdev->dev)) {
                if (test_and_clear_bit(1, &cdev->private->registered))
                        device_unregister(&cdev->dev);
        }
}

extern int css_get_ssd_info(struct subchannel *sch);

void
ccw_device_do_unreg_rereg(void *data)
{
        struct ccw_device *cdev;
        struct subchannel *sch;
        int need_rename;

        cdev = data;
        sch = to_subchannel(cdev->dev.parent);
        if (cdev->private->dev_id.devno != sch->schib.pmcw.dev) {
                /*
                 * The device number has changed. This is usually only when
                 * a device has been detached under VM and then re-appeared
                 * on another subchannel because of a different attachment
                 * order than before. Ideally, we should should just switch
                 * subchannels, but unfortunately, this is not possible with
                 * the current implementation.
                 * Instead, we search for the old subchannel for this device
                 * number and deregister so there are no collisions with the
                 * newly registered ccw_device.
                 * FIXME: Find another solution so the block layer doesn't
                 *        get possibly sick...
                 */
                struct ccw_device *other_cdev;
                struct ccw_dev_id dev_id;

                need_rename = 1;
                dev_id.devno = sch->schib.pmcw.dev;
                dev_id.ssid = sch->schid.ssid;
                other_cdev = get_disc_ccwdev_by_dev_id(&dev_id, cdev);
                if (other_cdev) {
                        struct subchannel *other_sch;

                        other_sch = to_subchannel(other_cdev->dev.parent);
                        if (get_device(&other_sch->dev)) {
                                stsch(other_sch->schid, &other_sch->schib);
                                if (other_sch->schib.pmcw.dnv) {
                                        other_sch->schib.pmcw.intparm = 0;
                                        cio_modify(other_sch);
                                }
                                css_sch_device_unregister(other_sch);
                        }
                }
                /* Update ssd info here. */
                css_get_ssd_info(sch);
                cdev->private->dev_id.devno = sch->schib.pmcw.dev;
        } else
                need_rename = 0;
        device_remove_files(&cdev->dev);
        if (test_and_clear_bit(1, &cdev->private->registered))
                device_del(&cdev->dev);
        if (need_rename)
                snprintf (cdev->dev.bus_id, BUS_ID_SIZE, "0.%x.%04x",
                          sch->schid.ssid, sch->schib.pmcw.dev);
        PREPARE_WORK(&cdev->private->kick_work,
                     ccw_device_add_changed, cdev);
        queue_work(ccw_device_work, &cdev->private->kick_work);
}

static void
ccw_device_release(struct device *dev)
{
        struct ccw_device *cdev;

        cdev = to_ccwdev(dev);
        kfree(cdev->private);
        kfree(cdev);
}

/*
 * Register recognized device.
 */
static void
io_subchannel_register(void *data)
{
        struct ccw_device *cdev;
        struct subchannel *sch;
        int ret;
        unsigned long flags;

        cdev = data;
        sch = to_subchannel(cdev->dev.parent);

        /*
         * io_subchannel_register() will also be called after device
         * recognition has been done for a boxed device (which will already
         * be registered). We need to reprobe since we may now have sense id
         * information.
         */
        if (klist_node_attached(&cdev->dev.knode_parent)) {
                if (!cdev->drv) {
                        ret = device_reprobe(&cdev->dev);
                        if (ret)
                                /* We can't do much here. */
                                dev_info(&cdev->dev, "device_reprobe() returned"
                                         " %d\n", ret);
                }
                goto out;
        }
        /* make it known to the system */
        ret = ccw_device_register(cdev);
        if (ret) {
                printk (KERN_WARNING "%s: could not register %s\n",
                        __func__, cdev->dev.bus_id);
                put_device(&cdev->dev);
                spin_lock_irqsave(&sch->lock, flags);
                sch->dev.driver_data = NULL;
                spin_unlock_irqrestore(&sch->lock, flags);
                kfree (cdev->private);
                kfree (cdev);
                put_device(&sch->dev);
                if (atomic_dec_and_test(&ccw_device_init_count))
                        wake_up(&ccw_device_init_wq);
                return;
        }

        ret = subchannel_add_files(cdev->dev.parent);
        if (ret)
                printk(KERN_WARNING "%s: could not add attributes to %s\n",
                       __func__, sch->dev.bus_id);
        put_device(&cdev->dev);
out:
        cdev->private->flags.recog_done = 1;
        put_device(&sch->dev);
        wake_up(&cdev->private->wait_q);
        if (atomic_dec_and_test(&ccw_device_init_count))
                wake_up(&ccw_device_init_wq);
}

void
ccw_device_call_sch_unregister(void *data)
{
        struct ccw_device *cdev = data;
        struct subchannel *sch;

        sch = to_subchannel(cdev->dev.parent);
        css_sch_device_unregister(sch);
        /* Reset intparm to zeroes. */
        sch->schib.pmcw.intparm = 0;
        cio_modify(sch);
        put_device(&cdev->dev);
        put_device(&sch->dev);
}

/*
 * subchannel recognition done. Called from the state machine.
 */
void
io_subchannel_recog_done(struct ccw_device *cdev)
{
        struct subchannel *sch;

        if (css_init_done == 0) {
                cdev->private->flags.recog_done = 1;
                return;
        }
        switch (cdev->private->state) {
        case DEV_STATE_NOT_OPER:
                cdev->private->flags.recog_done = 1;
                /* Remove device found not operational. */
                if (!get_device(&cdev->dev))
                        break;
                sch = to_subchannel(cdev->dev.parent);
                PREPARE_WORK(&cdev->private->kick_work,
                             ccw_device_call_sch_unregister, cdev);
                queue_work(slow_path_wq, &cdev->private->kick_work);
                if (atomic_dec_and_test(&ccw_device_init_count))
                        wake_up(&ccw_device_init_wq);
                break;
        case DEV_STATE_BOXED:
                /* Device did not respond in time. */
        case DEV_STATE_OFFLINE:
                /* 
                 * We can't register the device in interrupt context so
                 * we schedule a work item.
                 */
                if (!get_device(&cdev->dev))
                        break;
                PREPARE_WORK(&cdev->private->kick_work,
                             io_subchannel_register, cdev);
                queue_work(slow_path_wq, &cdev->private->kick_work);
                break;
        }
}

static int
io_subchannel_recog(struct ccw_device *cdev, struct subchannel *sch)
{
        int rc;
        struct ccw_device_private *priv;

        sch->dev.driver_data = cdev;
        sch->driver = &io_subchannel_driver;
        cdev->ccwlock = &sch->lock;

        /* Init private data. */
        priv = cdev->private;
        priv->dev_id.devno = sch->schib.pmcw.dev;
        priv->dev_id.ssid = sch->schid.ssid;
        priv->schid = sch->schid;
        priv->state = DEV_STATE_NOT_OPER;
        INIT_LIST_HEAD(&priv->cmb_list);
        init_waitqueue_head(&priv->wait_q);
        init_timer(&priv->timer);

        /* Set an initial name for the device. */
        snprintf (cdev->dev.bus_id, BUS_ID_SIZE, "0.%x.%04x",
                  sch->schid.ssid, sch->schib.pmcw.dev);

        /* Increase counter of devices currently in recognition. */
        atomic_inc(&ccw_device_init_count);

        /* Start async. device sensing. */
        spin_lock_irq(&sch->lock);
        rc = ccw_device_recognition(cdev);
        spin_unlock_irq(&sch->lock);
        if (rc) {
                if (atomic_dec_and_test(&ccw_device_init_count))
                        wake_up(&ccw_device_init_wq);
        }
        return rc;
}

static int
io_subchannel_probe (struct subchannel *sch)
{
        struct ccw_device *cdev;
        int rc;
        unsigned long flags;

        if (sch->dev.driver_data) {
                /*
                 * This subchannel already has an associated ccw_device.
                 * Register it and exit. This happens for all early
                 * device, e.g. the console.
                 */
                cdev = sch->dev.driver_data;
                device_initialize(&cdev->dev);
                ccw_device_register(cdev);
                subchannel_add_files(&sch->dev);
                /*
                 * Check if the device is already online. If it is
                 * the reference count needs to be corrected
                 * (see ccw_device_online and css_init_done for the
                 * ugly details).
                 */
                if (cdev->private->state != DEV_STATE_NOT_OPER &&
                    cdev->private->state != DEV_STATE_OFFLINE &&
                    cdev->private->state != DEV_STATE_BOXED)
                        get_device(&cdev->dev);
                return 0;
        }
        cdev = kzalloc (sizeof(*cdev), GFP_KERNEL);
        if (!cdev)
                return -ENOMEM;
        cdev->private = kzalloc(sizeof(struct ccw_device_private),
                                GFP_KERNEL | GFP_DMA);
        if (!cdev->private) {
                kfree(cdev);
                return -ENOMEM;
        }
        atomic_set(&cdev->private->onoff, 0);
        cdev->dev.parent = &sch->dev;
        cdev->dev.release = ccw_device_release;
        INIT_LIST_HEAD(&cdev->private->kick_work.entry);
        /* Do first half of device_register. */
        device_initialize(&cdev->dev);

        if (!get_device(&sch->dev)) {
                if (cdev->dev.release)
                        cdev->dev.release(&cdev->dev);
                return -ENODEV;
        }

        rc = io_subchannel_recog(cdev, sch);
        if (rc) {
                spin_lock_irqsave(&sch->lock, flags);
                sch->dev.driver_data = NULL;
                spin_unlock_irqrestore(&sch->lock, flags);
                if (cdev->dev.release)
                        cdev->dev.release(&cdev->dev);
        }

        return rc;
}

static void
ccw_device_unregister(void *data)
{
        struct ccw_device *cdev;

        cdev = (struct ccw_device *)data;
        if (test_and_clear_bit(1, &cdev->private->registered))
                device_unregister(&cdev->dev);
        put_device(&cdev->dev);
}

static int
io_subchannel_remove (struct subchannel *sch)
{
        struct ccw_device *cdev;
        unsigned long flags;

        if (!sch->dev.driver_data)
                return 0;
        cdev = sch->dev.driver_data;
        /* Set ccw device to not operational and drop reference. */
        spin_lock_irqsave(cdev->ccwlock, flags);
        sch->dev.driver_data = NULL;
        cdev->private->state = DEV_STATE_NOT_OPER;
        spin_unlock_irqrestore(cdev->ccwlock, flags);
        /*
         * Put unregistration on workqueue to avoid livelocks on the css bus
         * semaphore.
         */
        if (get_device(&cdev->dev)) {
                PREPARE_WORK(&cdev->private->kick_work,
                             ccw_device_unregister, cdev);
                queue_work(ccw_device_work, &cdev->private->kick_work);
        }
        return 0;
}

static int
io_subchannel_notify(struct device *dev, int event)
{
        struct ccw_device *cdev;

        cdev = dev->driver_data;
        if (!cdev)
                return 0;
        if (!cdev->drv)
                return 0;
        if (!cdev->online)
                return 0;
        return cdev->drv->notify ? cdev->drv->notify(cdev, event) : 0;
}

static void
io_subchannel_verify(struct device *dev)
{
        struct ccw_device *cdev;

        cdev = dev->driver_data;
        if (cdev)
                dev_fsm_event(cdev, DEV_EVENT_VERIFY);
}

static void
io_subchannel_ioterm(struct device *dev)
{
        struct ccw_device *cdev;

        cdev = dev->driver_data;
        if (!cdev)
                return;
        /* Internal I/O will be retried by the interrupt handler. */
        if (cdev->private->flags.intretry)
                return;
        cdev->private->state = DEV_STATE_CLEAR_VERIFY;
        if (cdev->handler)
                cdev->handler(cdev, cdev->private->intparm,
                              ERR_PTR(-EIO));
}

static void
io_subchannel_shutdown(struct subchannel *sch)
{
        struct ccw_device *cdev;
        int ret;

        cdev = sch->dev.driver_data;

        if (cio_is_console(sch->schid))
                return;
        if (!sch->schib.pmcw.ena)
                /* Nothing to do. */
                return;
        ret = cio_disable_subchannel(sch);
        if (ret != -EBUSY)
                /* Subchannel is disabled, we're done. */
                return;
        cdev->private->state = DEV_STATE_QUIESCE;
        if (cdev->handler)
                cdev->handler(cdev, cdev->private->intparm,
                              ERR_PTR(-EIO));
        ret = ccw_device_cancel_halt_clear(cdev);
        if (ret == -EBUSY) {
                ccw_device_set_timeout(cdev, HZ/10);
                wait_event(cdev->private->wait_q, dev_fsm_final_state(cdev));
        }
        cio_disable_subchannel(sch);
}

#ifdef CONFIG_CCW_CONSOLE
static struct ccw_device console_cdev;
static struct ccw_device_private console_private;
static int console_cdev_in_use;

static int
ccw_device_console_enable (struct ccw_device *cdev, struct subchannel *sch)
{
        int rc;

        /* Initialize the ccw_device structure. */
        cdev->dev.parent= &sch->dev;
        rc = io_subchannel_recog(cdev, sch);
        if (rc)
                return rc;

        /* Now wait for the async. recognition to come to an end. */
        spin_lock_irq(cdev->ccwlock);
        while (!dev_fsm_final_state(cdev))
                wait_cons_dev();
        rc = -EIO;
        if (cdev->private->state != DEV_STATE_OFFLINE)
                goto out_unlock;
        ccw_device_online(cdev);
        while (!dev_fsm_final_state(cdev))
                wait_cons_dev();
        if (cdev->private->state != DEV_STATE_ONLINE)
                goto out_unlock;
        rc = 0;
out_unlock:
        spin_unlock_irq(cdev->ccwlock);
        return 0;
}

struct ccw_device *
ccw_device_probe_console(void)
{
        struct subchannel *sch;
        int ret;

        if (xchg(&console_cdev_in_use, 1) != 0)
                return ERR_PTR(-EBUSY);
        sch = cio_probe_console();
        if (IS_ERR(sch)) {
                console_cdev_in_use = 0;
                return (void *) sch;
        }
        memset(&console_cdev, 0, sizeof(struct ccw_device));
        memset(&console_private, 0, sizeof(struct ccw_device_private));
        console_cdev.private = &console_private;
        ret = ccw_device_console_enable(&console_cdev, sch);
        if (ret) {
                cio_release_console();
                console_cdev_in_use = 0;
                return ERR_PTR(ret);
        }
        console_cdev.online = 1;
        return &console_cdev;
}
#endif

/*
 * get ccw_device matching the busid, but only if owned by cdrv
 */
static int
__ccwdev_check_busid(struct device *dev, void *id)
{
        char *bus_id;

        bus_id = id;

        return (strncmp(bus_id, dev->bus_id, BUS_ID_SIZE) == 0);
}


struct ccw_device *
get_ccwdev_by_busid(struct ccw_driver *cdrv, const char *bus_id)
{
        struct device *dev;
        struct device_driver *drv;

        drv = get_driver(&cdrv->driver);
        if (!drv)
                return NULL;

        dev = driver_find_device(drv, NULL, (void *)bus_id,
                                 __ccwdev_check_busid);
        put_driver(drv);

        return dev ? to_ccwdev(dev) : NULL;
}

/************************** device driver handling ************************/

/* This is the implementation of the ccw_driver class. The probe, remove
 * and release methods are initially very similar to the device_driver
 * implementations, with the difference that they have ccw_device
 * arguments.
 *
 * A ccw driver also contains the information that is needed for
 * device matching.
 */
static int
ccw_device_probe (struct device *dev)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_driver *cdrv = to_ccwdrv(dev->driver);
        int ret;

        cdev->drv = cdrv; /* to let the driver call _set_online */

        ret = cdrv->probe ? cdrv->probe(cdev) : -ENODEV;

        if (ret) {
                cdev->drv = NULL;
                return ret;
        }

        return 0;
}

static int
ccw_device_remove (struct device *dev)
{
        struct ccw_device *cdev = to_ccwdev(dev);
        struct ccw_driver *cdrv = cdev->drv;
        int ret;

        pr_debug("removing device %s\n", cdev->dev.bus_id);
        if (cdrv->remove)
                cdrv->remove(cdev);
        if (cdev->online) {
                cdev->online = 0;
                spin_lock_irq(cdev->ccwlock);
                ret = ccw_device_offline(cdev);
                spin_unlock_irq(cdev->ccwlock);
                if (ret == 0)
                        wait_event(cdev->private->wait_q,
                                   dev_fsm_final_state(cdev));
                else
                        //FIXME: we can't fail!
                        pr_debug("ccw_device_offline returned %d, device %s\n",
                                 ret, cdev->dev.bus_id);
        }
        ccw_device_set_timeout(cdev, 0);
        cdev->drv = NULL;
        return 0;
}

struct bus_type ccw_bus_type = {
        .name   = "ccw",
        .match  = ccw_bus_match,
        .uevent = ccw_uevent,
        .probe  = ccw_device_probe,
        .remove = ccw_device_remove,
};

int
ccw_driver_register (struct ccw_driver *cdriver)
{
        struct device_driver *drv = &cdriver->driver;

        drv->bus = &ccw_bus_type;
        drv->name = cdriver->name;

        return driver_register(drv);
}

void
ccw_driver_unregister (struct ccw_driver *cdriver)
{
        driver_unregister(&cdriver->driver);
}

/* Helper func for qdio. */
struct subchannel_id
ccw_device_get_subchannel_id(struct ccw_device *cdev)
{
        struct subchannel *sch;

        sch = to_subchannel(cdev->dev.parent);
        return sch->schid;
}

MODULE_LICENSE("GPL");
EXPORT_SYMBOL(ccw_device_set_online);
EXPORT_SYMBOL(ccw_device_set_offline);
EXPORT_SYMBOL(ccw_driver_register);
EXPORT_SYMBOL(ccw_driver_unregister);
EXPORT_SYMBOL(get_ccwdev_by_busid);
EXPORT_SYMBOL(ccw_bus_type);
EXPORT_SYMBOL(ccw_device_work);
EXPORT_SYMBOL(ccw_device_notify_work);
EXPORT_SYMBOL_GPL(ccw_device_get_subchannel_id);