virtio_ccw.c

// SPDX-License-Identifier: GPL-2.0
/*
 * ccw based virtio transport
 *
 * Copyright IBM Corp. 2012, 2014
 *
 *    Author(s): Cornelia Huck <cornelia.huck@de.ibm.com>
 */

#include <linux/kernel_stat.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/err.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/virtio_ring.h>
#include <linux/pfn.h>
#include <linux/async.h>
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/bitops.h>
#include <linux/moduleparam.h>
#include <linux/io.h>
#include <linux/kvm_para.h>
#include <linux/notifier.h>
#include <asm/diag.h>
#include <asm/setup.h>
#include <asm/irq.h>
#include <asm/cio.h>
#include <asm/ccwdev.h>
#include <asm/virtio-ccw.h>
#include <asm/isc.h>
#include <asm/airq.h>

/*
 * virtio related functions
 */

struct vq_config_block {
	__u16 index;
	__u16 num;
} __packed;

#define VIRTIO_CCW_CONFIG_SIZE 0x100
/* same as PCI config space size, should be enough for all drivers */

struct virtio_ccw_device {
	struct virtio_device vdev;
	__u8 *status;
	__u8 config[VIRTIO_CCW_CONFIG_SIZE];
	struct ccw_device *cdev;
	__u32 curr_io;
	int err;
	unsigned int revision; /* Transport revision */
	wait_queue_head_t wait_q;
	spinlock_t lock;
	struct mutex io_lock; /* Serializes I/O requests */
	struct list_head virtqueues;
	unsigned long indicators;
	unsigned long indicators2;
	struct vq_config_block *config_block;
	bool is_thinint;
	bool going_away;
	bool device_lost;
	unsigned int config_ready;
	void *airq_info;
};

struct vq_info_block_legacy {
	__u64 queue;
	__u32 align;
	__u16 index;
	__u16 num;
} __packed;

struct vq_info_block {
	__u64 desc;
	__u32 res0;
	__u16 index;
	__u16 num;
	__u64 avail;
	__u64 used;
} __packed;

struct virtio_feature_desc {
	__le32 features;
	__u8 index;
} __packed;

struct virtio_thinint_area {
	unsigned long summary_indicator;
	unsigned long indicator;
	u64 bit_nr;
	u8 isc;
} __packed;

struct virtio_rev_info {
	__u16 revision;
	__u16 length;
	__u8 data[];
};

/* the highest virtio-ccw revision we support */
#define VIRTIO_CCW_REV_MAX 1

struct virtio_ccw_vq_info {
	struct virtqueue *vq;
	int num;
	void *queue;
	union {
		struct vq_info_block s;
		struct vq_info_block_legacy l;
	} *info_block;
	int bit_nr;
	struct list_head node;
	long cookie;
};

#define VIRTIO_AIRQ_ISC IO_SCH_ISC /* inherit from subchannel */

#define VIRTIO_IV_BITS (L1_CACHE_BYTES * 8)
#define MAX_AIRQ_AREAS 20

static int virtio_ccw_use_airq = 1;

struct airq_info {
	rwlock_t lock;
	u8 summary_indicator;
	struct airq_struct airq;
	struct airq_iv *aiv;
};
static struct airq_info *airq_areas[MAX_AIRQ_AREAS];

#define CCW_CMD_SET_VQ 0x13
#define CCW_CMD_VDEV_RESET 0x33
#define CCW_CMD_SET_IND 0x43
#define CCW_CMD_SET_CONF_IND 0x53
#define CCW_CMD_READ_FEAT 0x12
#define CCW_CMD_WRITE_FEAT 0x11
#define CCW_CMD_READ_CONF 0x22
#define CCW_CMD_WRITE_CONF 0x21
#define CCW_CMD_WRITE_STATUS 0x31
#define CCW_CMD_READ_VQ_CONF 0x32
#define CCW_CMD_READ_STATUS 0x72
#define CCW_CMD_SET_IND_ADAPTER 0x73
#define CCW_CMD_SET_VIRTIO_REV 0x83

#define VIRTIO_CCW_DOING_SET_VQ 0x00010000
#define VIRTIO_CCW_DOING_RESET 0x00040000
#define VIRTIO_CCW_DOING_READ_FEAT 0x00080000
#define VIRTIO_CCW_DOING_WRITE_FEAT 0x00100000
#define VIRTIO_CCW_DOING_READ_CONFIG 0x00200000
#define VIRTIO_CCW_DOING_WRITE_CONFIG 0x00400000
#define VIRTIO_CCW_DOING_WRITE_STATUS 0x00800000
#define VIRTIO_CCW_DOING_SET_IND 0x01000000
#define VIRTIO_CCW_DOING_READ_VQ_CONF 0x02000000
#define VIRTIO_CCW_DOING_SET_CONF_IND 0x04000000
#define VIRTIO_CCW_DOING_SET_IND_ADAPTER 0x08000000
#define VIRTIO_CCW_DOING_SET_VIRTIO_REV 0x10000000
#define VIRTIO_CCW_DOING_READ_STATUS 0x20000000
#define VIRTIO_CCW_INTPARM_MASK 0xffff0000

static struct virtio_ccw_device *to_vc_device(struct virtio_device *vdev)
{
	return container_of(vdev, struct virtio_ccw_device, vdev);
}

static void drop_airq_indicator(struct virtqueue *vq, struct airq_info *info)
{
	unsigned long i, flags;

	write_lock_irqsave(&info->lock, flags);
	for (i = 0; i < airq_iv_end(info->aiv); i++) {
		if (vq == (void *)airq_iv_get_ptr(info->aiv, i)) {
			airq_iv_free_bit(info->aiv, i);
			airq_iv_set_ptr(info->aiv, i, 0);
			break;
		}
	}
	write_unlock_irqrestore(&info->lock, flags);
}

static void virtio_airq_handler(struct airq_struct *airq)
{
	struct airq_info *info = container_of(airq, struct airq_info, airq);
	unsigned long ai;

	inc_irq_stat(IRQIO_VAI);
	read_lock(&info->lock);
	/* Walk through indicators field, summary indicator active. */
	for (ai = 0;;) {
		ai = airq_iv_scan(info->aiv, ai, airq_iv_end(info->aiv));
		if (ai == -1UL)
			break;
		vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
	}
	info->summary_indicator = 0;
	smp_wmb();
	/* Walk through indicators field, summary indicator not active. */
	for (ai = 0;;) {
		ai = airq_iv_scan(info->aiv, ai, airq_iv_end(info->aiv));
		if (ai == -1UL)
			break;
		vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
	}
	read_unlock(&info->lock);
}

static struct airq_info *new_airq_info(void)
{
	struct airq_info *info;
	int rc;

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (!info)
		return NULL;
	rwlock_init(&info->lock);
	info->aiv = airq_iv_create(VIRTIO_IV_BITS, AIRQ_IV_ALLOC | AIRQ_IV_PTR);
	if (!info->aiv) {
		kfree(info);
		return NULL;
	}
	info->airq.handler = virtio_airq_handler;
	info->airq.lsi_ptr = &info->summary_indicator;
	info->airq.lsi_mask = 0xff;
	info->airq.isc = VIRTIO_AIRQ_ISC;
	rc = register_adapter_interrupt(&info->airq);
	if (rc) {
		airq_iv_release(info->aiv);
		kfree(info);
		return NULL;
	}
	return info;
}

static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs,
					u64 *first, void **airq_info)
{
	int i, j;
	struct airq_info *info;
	unsigned long indicator_addr = 0;
	unsigned long bit, flags;

	for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) {
		if (!airq_areas[i])
			airq_areas[i] = new_airq_info();
		info = airq_areas[i];
		if (!info)
			return 0;
		write_lock_irqsave(&info->lock, flags);
		bit = airq_iv_alloc(info->aiv, nvqs);
		if (bit == -1UL) {
			/* Not enough vacancies. */
			write_unlock_irqrestore(&info->lock, flags);
			continue;
		}
		*first = bit;
		*airq_info = info;
		indicator_addr = (unsigned long)info->aiv->vector;
		for (j = 0; j < nvqs; j++) {
			airq_iv_set_ptr(info->aiv, bit + j,
					(unsigned long)vqs[j]);
		}
		write_unlock_irqrestore(&info->lock, flags);
	}
	return indicator_addr;
}

static void virtio_ccw_drop_indicators(struct virtio_ccw_device *vcdev)
{
	struct virtio_ccw_vq_info *info;

	if (!vcdev->airq_info)
		return;
	list_for_each_entry(info, &vcdev->virtqueues, node)
		drop_airq_indicator(info->vq, vcdev->airq_info);
}

static int doing_io(struct virtio_ccw_device *vcdev, __u32 flag)
{
	unsigned long flags;
	__u32 ret;

	spin_lock_irqsave(get_ccwdev_lock(vcdev->cdev), flags);
	if (vcdev->err)
		ret = 0;
	else
		ret = vcdev->curr_io & flag;
	spin_unlock_irqrestore(get_ccwdev_lock(vcdev->cdev), flags);
	return ret;
}

static int ccw_io_helper(struct virtio_ccw_device *vcdev,
			 struct ccw1 *ccw, __u32 intparm)
{
	int ret;
	unsigned long flags;
	int flag = intparm & VIRTIO_CCW_INTPARM_MASK;

	mutex_lock(&vcdev->io_lock);
	do {
		spin_lock_irqsave(get_ccwdev_lock(vcdev->cdev), flags);
		ret = ccw_device_start(vcdev->cdev, ccw, intparm, 0, 0);
		if (!ret) {
			if (!vcdev->curr_io)
				vcdev->err = 0;
			vcdev->curr_io |= flag;
		}
		spin_unlock_irqrestore(get_ccwdev_lock(vcdev->cdev), flags);
		cpu_relax();
	} while (ret == -EBUSY);
	wait_event(vcdev->wait_q, doing_io(vcdev, flag) == 0);
	ret = ret ? ret : vcdev->err;
	mutex_unlock(&vcdev->io_lock);
	return ret;
}

static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev,
				      struct ccw1 *ccw)
{
	int ret;
	unsigned long *indicatorp = NULL;
	struct virtio_thinint_area *thinint_area = NULL;
	struct airq_info *airq_info = vcdev->airq_info;

	if (vcdev->is_thinint) {
		thinint_area = kzalloc(sizeof(*thinint_area),
				       GFP_DMA | GFP_KERNEL);
		if (!thinint_area)
			return;
		thinint_area->summary_indicator =
			(unsigned long) &airq_info->summary_indicator;
		thinint_area->isc = VIRTIO_AIRQ_ISC;
		ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
		ccw->count = sizeof(*thinint_area);
		ccw->cda = (__u32)(unsigned long) thinint_area;
	} else {
		/* payload is the address of the indicators */
		indicatorp = kmalloc(sizeof(&vcdev->indicators),
				     GFP_DMA | GFP_KERNEL);
		if (!indicatorp)
			return;
		*indicatorp = 0;
		ccw->cmd_code = CCW_CMD_SET_IND;
		ccw->count = sizeof(&vcdev->indicators);
		ccw->cda = (__u32)(unsigned long) indicatorp;
	}
	/* Deregister indicators from host. */
	vcdev->indicators = 0;
	ccw->flags = 0;
	ret = ccw_io_helper(vcdev, ccw,
			    vcdev->is_thinint ?
			    VIRTIO_CCW_DOING_SET_IND_ADAPTER :
			    VIRTIO_CCW_DOING_SET_IND);
	if (ret && (ret != -ENODEV))
		dev_info(&vcdev->cdev->dev,
			 "Failed to deregister indicators (%d)\n", ret);
	else if (vcdev->is_thinint)
		virtio_ccw_drop_indicators(vcdev);
	kfree(indicatorp);
	kfree(thinint_area);
}

static inline long __do_kvm_notify(struct subchannel_id schid,
				   unsigned long queue_index,
				   long cookie)
{
	register unsigned long __nr asm("1") = KVM_S390_VIRTIO_CCW_NOTIFY;
	register struct subchannel_id __schid asm("2") = schid;
	register unsigned long __index asm("3") = queue_index;
	register long __rc asm("2");
	register long __cookie asm("4") = cookie;

	asm volatile ("diag 2,4,0x500\n"
		      : "=d" (__rc) : "d" (__nr), "d" (__schid), "d" (__index),
		      "d"(__cookie)
		      : "memory", "cc");
	return __rc;
}

static inline long do_kvm_notify(struct subchannel_id schid,
				 unsigned long queue_index,
				 long cookie)
{
	diag_stat_inc(DIAG_STAT_X500);
	return __do_kvm_notify(schid, queue_index, cookie);
}

static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
{
	struct virtio_ccw_vq_info *info = vq->priv;
	struct virtio_ccw_device *vcdev;
	struct subchannel_id schid;

	vcdev = to_vc_device(info->vq->vdev);
	ccw_device_get_schid(vcdev->cdev, &schid);
	info->cookie = do_kvm_notify(schid, vq->index, info->cookie);
	if (info->cookie < 0)
		return false;
	return true;
}

static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
				   struct ccw1 *ccw, int index)
{
	int ret;

	vcdev->config_block->index = index;
	ccw->cmd_code = CCW_CMD_READ_VQ_CONF;
	ccw->flags = 0;
	ccw->count = sizeof(struct vq_config_block);
	ccw->cda = (__u32)(unsigned long)(vcdev->config_block);
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_VQ_CONF);
	if (ret)
		return ret;
	return vcdev->config_block->num ?: -ENOENT;
}

static void virtio_ccw_del_vq(struct virtqueue *vq, struct ccw1 *ccw)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vq->vdev);
	struct virtio_ccw_vq_info *info = vq->priv;
	unsigned long flags;
	unsigned long size;
	int ret;
	unsigned int index = vq->index;

	/* Remove from our list. */
	spin_lock_irqsave(&vcdev->lock, flags);
	list_del(&info->node);
	spin_unlock_irqrestore(&vcdev->lock, flags);

	/* Release from host. */
	if (vcdev->revision == 0) {
		info->info_block->l.queue = 0;
		info->info_block->l.align = 0;
		info->info_block->l.index = index;
		info->info_block->l.num = 0;
		ccw->count = sizeof(info->info_block->l);
	} else {
		info->info_block->s.desc = 0;
		info->info_block->s.index = index;
		info->info_block->s.num = 0;
		info->info_block->s.avail = 0;
		info->info_block->s.used = 0;
		ccw->count = sizeof(info->info_block->s);
	}
	ccw->cmd_code = CCW_CMD_SET_VQ;
	ccw->flags = 0;
	ccw->cda = (__u32)(unsigned long)(info->info_block);
	ret = ccw_io_helper(vcdev, ccw,
			    VIRTIO_CCW_DOING_SET_VQ | index);
	/*
	 * -ENODEV isn't considered an error: The device is gone anyway.
	 * This may happen on device detach.
	 */
	if (ret && (ret != -ENODEV))
		dev_warn(&vq->vdev->dev, "Error %d while deleting queue %d\n",
			 ret, index);

	vring_del_virtqueue(vq);
	size = PAGE_ALIGN(vring_size(info->num, KVM_VIRTIO_CCW_RING_ALIGN));
	free_pages_exact(info->queue, size);
	kfree(info->info_block);
	kfree(info);
}

static void virtio_ccw_del_vqs(struct virtio_device *vdev)
{
	struct virtqueue *vq, *n;
	struct ccw1 *ccw;
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return;

	virtio_ccw_drop_indicator(vcdev, ccw);

	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
		virtio_ccw_del_vq(vq, ccw);

	kfree(ccw);
}

static struct virtqueue *virtio_ccw_setup_vq(struct virtio_device *vdev,
					     int i, vq_callback_t *callback,
					     const char *name, bool ctx,
					     struct ccw1 *ccw)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	int err;
	struct virtqueue *vq = NULL;
	struct virtio_ccw_vq_info *info;
	unsigned long size = 0; /* silence the compiler */
	unsigned long flags;

	/* Allocate queue. */
	info = kzalloc(sizeof(struct virtio_ccw_vq_info), GFP_KERNEL);
	if (!info) {
		dev_warn(&vcdev->cdev->dev, "no info\n");
		err = -ENOMEM;
		goto out_err;
	}
	info->info_block = kzalloc(sizeof(*info->info_block),
				   GFP_DMA | GFP_KERNEL);
	if (!info->info_block) {
		dev_warn(&vcdev->cdev->dev, "no info block\n");
		err = -ENOMEM;
		goto out_err;
	}
	info->num = virtio_ccw_read_vq_conf(vcdev, ccw, i);
	if (info->num < 0) {
		err = info->num;
		goto out_err;
	}
	size = PAGE_ALIGN(vring_size(info->num, KVM_VIRTIO_CCW_RING_ALIGN));
	info->queue = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO);
	if (info->queue == NULL) {
		dev_warn(&vcdev->cdev->dev, "no queue\n");
		err = -ENOMEM;
		goto out_err;
	}

	vq = vring_new_virtqueue(i, info->num, KVM_VIRTIO_CCW_RING_ALIGN, vdev,
				 true, ctx, info->queue, virtio_ccw_kvm_notify,
				 callback, name);
	if (!vq) {
		/* For now, we fail if we can't get the requested size. */
		dev_warn(&vcdev->cdev->dev, "no vq\n");
		err = -ENOMEM;
		goto out_err;
	}

	/* Register it with the host. */
	if (vcdev->revision == 0) {
		info->info_block->l.queue = (__u64)info->queue;
		info->info_block->l.align = KVM_VIRTIO_CCW_RING_ALIGN;
		info->info_block->l.index = i;
		info->info_block->l.num = info->num;
		ccw->count = sizeof(info->info_block->l);
	} else {
		info->info_block->s.desc = (__u64)info->queue;
		info->info_block->s.index = i;
		info->info_block->s.num = info->num;
		info->info_block->s.avail = (__u64)virtqueue_get_avail(vq);
		info->info_block->s.used = (__u64)virtqueue_get_used(vq);
		ccw->count = sizeof(info->info_block->s);
	}
	ccw->cmd_code = CCW_CMD_SET_VQ;
	ccw->flags = 0;
	ccw->cda = (__u32)(unsigned long)(info->info_block);
	err = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_VQ | i);
	if (err) {
		dev_warn(&vcdev->cdev->dev, "SET_VQ failed\n");
		goto out_err;
	}

	info->vq = vq;
	vq->priv = info;

	/* Save it to our list. */
	spin_lock_irqsave(&vcdev->lock, flags);
	list_add(&info->node, &vcdev->virtqueues);
	spin_unlock_irqrestore(&vcdev->lock, flags);

	return vq;

out_err:
	if (vq)
		vring_del_virtqueue(vq);
	if (info) {
		if (info->queue)
			free_pages_exact(info->queue, size);
		kfree(info->info_block);
	}
	kfree(info);
	return ERR_PTR(err);
}

static int virtio_ccw_register_adapter_ind(struct virtio_ccw_device *vcdev,
					   struct virtqueue *vqs[], int nvqs,
					   struct ccw1 *ccw)
{
	int ret;
	struct virtio_thinint_area *thinint_area = NULL;
	struct airq_info *info;

	thinint_area = kzalloc(sizeof(*thinint_area), GFP_DMA | GFP_KERNEL);
	if (!thinint_area) {
		ret = -ENOMEM;
		goto out;
	}
	/* Try to get an indicator. */
	thinint_area->indicator = get_airq_indicator(vqs, nvqs,
						     &thinint_area->bit_nr,
						     &vcdev->airq_info);
	if (!thinint_area->indicator) {
		ret = -ENOSPC;
		goto out;
	}
	info = vcdev->airq_info;
	thinint_area->summary_indicator =
		(unsigned long) &info->summary_indicator;
	thinint_area->isc = VIRTIO_AIRQ_ISC;
	ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
	ccw->flags = CCW_FLAG_SLI;
	ccw->count = sizeof(*thinint_area);
	ccw->cda = (__u32)(unsigned long)thinint_area;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_IND_ADAPTER);
	if (ret) {
		if (ret == -EOPNOTSUPP) {
			/*
			 * The host does not support adapter interrupts
			 * for virtio-ccw, stop trying.
			 */
			virtio_ccw_use_airq = 0;
			pr_info("Adapter interrupts unsupported on host\n");
		} else
			dev_warn(&vcdev->cdev->dev,
				 "enabling adapter interrupts = %d\n", ret);
		virtio_ccw_drop_indicators(vcdev);
	}
out:
	kfree(thinint_area);
	return ret;
}

static int virtio_ccw_find_vqs(struct virtio_device *vdev, unsigned nvqs,
			       struct virtqueue *vqs[],
			       vq_callback_t *callbacks[],
			       const char * const names[],
			       const bool *ctx,
			       struct irq_affinity *desc)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	unsigned long *indicatorp = NULL;
	int ret, i;
	struct ccw1 *ccw;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return -ENOMEM;

	for (i = 0; i < nvqs; ++i) {
		vqs[i] = virtio_ccw_setup_vq(vdev, i, callbacks[i], names[i],
					     ctx ? ctx[i] : false, ccw);
		if (IS_ERR(vqs[i])) {
			ret = PTR_ERR(vqs[i]);
			vqs[i] = NULL;
			goto out;
		}
	}
	ret = -ENOMEM;
	/*
	 * We need a data area under 2G to communicate. Our payload is
	 * the address of the indicators.
	*/
	indicatorp = kmalloc(sizeof(&vcdev->indicators), GFP_DMA | GFP_KERNEL);
	if (!indicatorp)
		goto out;
	*indicatorp = (unsigned long) &vcdev->indicators;
	if (vcdev->is_thinint) {
		ret = virtio_ccw_register_adapter_ind(vcdev, vqs, nvqs, ccw);
		if (ret)
			/* no error, just fall back to legacy interrupts */
			vcdev->is_thinint = false;
	}
	if (!vcdev->is_thinint) {
		/* Register queue indicators with host. */
		vcdev->indicators = 0;
		ccw->cmd_code = CCW_CMD_SET_IND;
		ccw->flags = 0;
		ccw->count = sizeof(&vcdev->indicators);
		ccw->cda = (__u32)(unsigned long) indicatorp;
		ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_IND);
		if (ret)
			goto out;
	}
	/* Register indicators2 with host for config changes */
	*indicatorp = (unsigned long) &vcdev->indicators2;
	vcdev->indicators2 = 0;
	ccw->cmd_code = CCW_CMD_SET_CONF_IND;
	ccw->flags = 0;
	ccw->count = sizeof(&vcdev->indicators2);
	ccw->cda = (__u32)(unsigned long) indicatorp;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_SET_CONF_IND);
	if (ret)
		goto out;

	kfree(indicatorp);
	kfree(ccw);
	return 0;
out:
	kfree(indicatorp);
	kfree(ccw);
	virtio_ccw_del_vqs(vdev);
	return ret;
}

static void virtio_ccw_reset(struct virtio_device *vdev)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	struct ccw1 *ccw;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return;

	/* Zero status bits. */
	*vcdev->status = 0;

	/* Send a reset ccw on device. */
	ccw->cmd_code = CCW_CMD_VDEV_RESET;
	ccw->flags = 0;
	ccw->count = 0;
	ccw->cda = 0;
	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_RESET);
	kfree(ccw);
}

static u64 virtio_ccw_get_features(struct virtio_device *vdev)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	struct virtio_feature_desc *features;
	int ret;
	u64 rc;
	struct ccw1 *ccw;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return 0;

	features = kzalloc(sizeof(*features), GFP_DMA | GFP_KERNEL);
	if (!features) {
		rc = 0;
		goto out_free;
	}
	/* Read the feature bits from the host. */
	features->index = 0;
	ccw->cmd_code = CCW_CMD_READ_FEAT;
	ccw->flags = 0;
	ccw->count = sizeof(*features);
	ccw->cda = (__u32)(unsigned long)features;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_FEAT);
	if (ret) {
		rc = 0;
		goto out_free;
	}

	rc = le32_to_cpu(features->features);

	if (vcdev->revision == 0)
		goto out_free;

	/* Read second half of the feature bits from the host. */
	features->index = 1;
	ccw->cmd_code = CCW_CMD_READ_FEAT;
	ccw->flags = 0;
	ccw->count = sizeof(*features);
	ccw->cda = (__u32)(unsigned long)features;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_FEAT);
	if (ret == 0)
		rc |= (u64)le32_to_cpu(features->features) << 32;

out_free:
	kfree(features);
	kfree(ccw);
	return rc;
}

static int virtio_ccw_finalize_features(struct virtio_device *vdev)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	struct virtio_feature_desc *features;
	struct ccw1 *ccw;
	int ret;

	if (vcdev->revision >= 1 &&
	    !__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
		dev_err(&vdev->dev, "virtio: device uses revision 1 "
			"but does not have VIRTIO_F_VERSION_1\n");
		return -EINVAL;
	}

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return -ENOMEM;

	features = kzalloc(sizeof(*features), GFP_DMA | GFP_KERNEL);
	if (!features) {
		ret = -ENOMEM;
		goto out_free;
	}
	/* Give virtio_ring a chance to accept features. */
	vring_transport_features(vdev);

	features->index = 0;
	features->features = cpu_to_le32((u32)vdev->features);
	/* Write the first half of the feature bits to the host. */
	ccw->cmd_code = CCW_CMD_WRITE_FEAT;
	ccw->flags = 0;
	ccw->count = sizeof(*features);
	ccw->cda = (__u32)(unsigned long)features;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
	if (ret)
		goto out_free;

	if (vcdev->revision == 0)
		goto out_free;

	features->index = 1;
	features->features = cpu_to_le32(vdev->features >> 32);
	/* Write the second half of the feature bits to the host. */
	ccw->cmd_code = CCW_CMD_WRITE_FEAT;
	ccw->flags = 0;
	ccw->count = sizeof(*features);
	ccw->cda = (__u32)(unsigned long)features;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);

out_free:
	kfree(features);
	kfree(ccw);

	return ret;
}

static void virtio_ccw_get_config(struct virtio_device *vdev,
				  unsigned int offset, void *buf, unsigned len)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	int ret;
	struct ccw1 *ccw;
	void *config_area;
	unsigned long flags;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return;

	config_area = kzalloc(VIRTIO_CCW_CONFIG_SIZE, GFP_DMA | GFP_KERNEL);
	if (!config_area)
		goto out_free;

	/* Read the config area from the host. */
	ccw->cmd_code = CCW_CMD_READ_CONF;
	ccw->flags = 0;
	ccw->count = offset + len;
	ccw->cda = (__u32)(unsigned long)config_area;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_CONFIG);
	if (ret)
		goto out_free;

	spin_lock_irqsave(&vcdev->lock, flags);
	memcpy(vcdev->config, config_area, offset + len);
	if (vcdev->config_ready < offset + len)
		vcdev->config_ready = offset + len;
	spin_unlock_irqrestore(&vcdev->lock, flags);
	if (buf)
		memcpy(buf, config_area + offset, len);

out_free:
	kfree(config_area);
	kfree(ccw);
}

static void virtio_ccw_set_config(struct virtio_device *vdev,
				  unsigned int offset, const void *buf,
				  unsigned len)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	struct ccw1 *ccw;
	void *config_area;
	unsigned long flags;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return;

	config_area = kzalloc(VIRTIO_CCW_CONFIG_SIZE, GFP_DMA | GFP_KERNEL);
	if (!config_area)
		goto out_free;

	/* Make sure we don't overwrite fields. */
	if (vcdev->config_ready < offset)
		virtio_ccw_get_config(vdev, 0, NULL, offset);
	spin_lock_irqsave(&vcdev->lock, flags);
	memcpy(&vcdev->config[offset], buf, len);
	/* Write the config area to the host. */
	memcpy(config_area, vcdev->config, sizeof(vcdev->config));
	spin_unlock_irqrestore(&vcdev->lock, flags);
	ccw->cmd_code = CCW_CMD_WRITE_CONF;
	ccw->flags = 0;
	ccw->count = offset + len;
	ccw->cda = (__u32)(unsigned long)config_area;
	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_CONFIG);

out_free:
	kfree(config_area);
	kfree(ccw);
}

static u8 virtio_ccw_get_status(struct virtio_device *vdev)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	u8 old_status = *vcdev->status;
	struct ccw1 *ccw;

	if (vcdev->revision < 1)
		return *vcdev->status;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return old_status;

	ccw->cmd_code = CCW_CMD_READ_STATUS;
	ccw->flags = 0;
	ccw->count = sizeof(*vcdev->status);
	ccw->cda = (__u32)(unsigned long)vcdev->status;
	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_STATUS);
/*
 * If the channel program failed (should only happen if the device
 * was hotunplugged, and then we clean up via the machine check
 * handler anyway), vcdev->status was not overwritten and we just
 * return the old status, which is fine.
*/
	kfree(ccw);

	return *vcdev->status;
}

static void virtio_ccw_set_status(struct virtio_device *vdev, u8 status)
{
	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
	u8 old_status = *vcdev->status;
	struct ccw1 *ccw;
	int ret;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return;

	/* Write the status to the host. */
	*vcdev->status = status;
	ccw->cmd_code = CCW_CMD_WRITE_STATUS;
	ccw->flags = 0;
	ccw->count = sizeof(status);
	ccw->cda = (__u32)(unsigned long)vcdev->status;
	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_STATUS);
	/* Write failed? We assume status is unchanged. */
	if (ret)
		*vcdev->status = old_status;
	kfree(ccw);
}

static const struct virtio_config_ops virtio_ccw_config_ops = {
	.get_features = virtio_ccw_get_features,
	.finalize_features = virtio_ccw_finalize_features,
	.get = virtio_ccw_get_config,
	.set = virtio_ccw_set_config,
	.get_status = virtio_ccw_get_status,
	.set_status = virtio_ccw_set_status,
	.reset = virtio_ccw_reset,
	.find_vqs = virtio_ccw_find_vqs,
	.del_vqs = virtio_ccw_del_vqs,
};


/*
 * ccw bus driver related functions
 */

static void virtio_ccw_release_dev(struct device *_d)
{
	struct virtio_device *dev = dev_to_virtio(_d);
	struct virtio_ccw_device *vcdev = to_vc_device(dev);

	kfree(vcdev->status);
	kfree(vcdev->config_block);
	kfree(vcdev);
}

static int irb_is_error(struct irb *irb)
{
	if (scsw_cstat(&irb->scsw) != 0)
		return 1;
	if (scsw_dstat(&irb->scsw) & ~(DEV_STAT_CHN_END | DEV_STAT_DEV_END))
		return 1;
	if (scsw_cc(&irb->scsw) != 0)
		return 1;
	return 0;
}

static struct virtqueue *virtio_ccw_vq_by_ind(struct virtio_ccw_device *vcdev,
					      int index)
{
	struct virtio_ccw_vq_info *info;
	unsigned long flags;
	struct virtqueue *vq;

	vq = NULL;
	spin_lock_irqsave(&vcdev->lock, flags);
	list_for_each_entry(info, &vcdev->virtqueues, node) {
		if (info->vq->index == index) {
			vq = info->vq;
			break;
		}
	}
	spin_unlock_irqrestore(&vcdev->lock, flags);
	return vq;
}

static void virtio_ccw_check_activity(struct virtio_ccw_device *vcdev,
				      __u32 activity)
{
	if (vcdev->curr_io & activity) {
		switch (activity) {
		case VIRTIO_CCW_DOING_READ_FEAT:
		case VIRTIO_CCW_DOING_WRITE_FEAT:
		case VIRTIO_CCW_DOING_READ_CONFIG:
		case VIRTIO_CCW_DOING_WRITE_CONFIG:
		case VIRTIO_CCW_DOING_WRITE_STATUS:
		case VIRTIO_CCW_DOING_READ_STATUS:
		case VIRTIO_CCW_DOING_SET_VQ:
		case VIRTIO_CCW_DOING_SET_IND:
		case VIRTIO_CCW_DOING_SET_CONF_IND:
		case VIRTIO_CCW_DOING_RESET:
		case VIRTIO_CCW_DOING_READ_VQ_CONF:
		case VIRTIO_CCW_DOING_SET_IND_ADAPTER:
		case VIRTIO_CCW_DOING_SET_VIRTIO_REV:
			vcdev->curr_io &= ~activity;
			wake_up(&vcdev->wait_q);
			break;
		default:
			/* don't know what to do... */
			dev_warn(&vcdev->cdev->dev,
				 "Suspicious activity '%08x'\n", activity);
			WARN_ON(1);
			break;
		}
	}
}

static void virtio_ccw_int_handler(struct ccw_device *cdev,
				   unsigned long intparm,
				   struct irb *irb)
{
	__u32 activity = intparm & VIRTIO_CCW_INTPARM_MASK;
	struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
	int i;
	struct virtqueue *vq;

	if (!vcdev)
		return;
	if (IS_ERR(irb)) {
		vcdev->err = PTR_ERR(irb);
		virtio_ccw_check_activity(vcdev, activity);
		/* Don't poke around indicators, something's wrong. */
		return;
	}
	/* Check if it's a notification from the host. */
	if ((intparm == 0) &&
	    (scsw_stctl(&irb->scsw) ==
	     (SCSW_STCTL_ALERT_STATUS | SCSW_STCTL_STATUS_PEND))) {
		/* OK */
	}
	if (irb_is_error(irb)) {
		/* Command reject? */
		if ((scsw_dstat(&irb->scsw) & DEV_STAT_UNIT_CHECK) &&
		    (irb->ecw[0] & SNS0_CMD_REJECT))
			vcdev->err = -EOPNOTSUPP;
		else
			/* Map everything else to -EIO. */
			vcdev->err = -EIO;
	}
	virtio_ccw_check_activity(vcdev, activity);
	for_each_set_bit(i, &vcdev->indicators,
			 sizeof(vcdev->indicators) * BITS_PER_BYTE) {
		/* The bit clear must happen before the vring kick. */
		clear_bit(i, &vcdev->indicators);
		barrier();
		vq = virtio_ccw_vq_by_ind(vcdev, i);
		vring_interrupt(0, vq);
	}
	if (test_bit(0, &vcdev->indicators2)) {
		virtio_config_changed(&vcdev->vdev);
		clear_bit(0, &vcdev->indicators2);
	}
}

/*
 * We usually want to autoonline all devices, but give the admin
 * a way to exempt devices from this.
 */
#define __DEV_WORDS ((__MAX_SUBCHANNEL + (8*sizeof(long) - 1)) / \
		     (8*sizeof(long)))
static unsigned long devs_no_auto[__MAX_SSID + 1][__DEV_WORDS];

static char *no_auto = "";

module_param(no_auto, charp, 0444);
MODULE_PARM_DESC(no_auto, "list of ccw bus id ranges not to be auto-onlined");

static int virtio_ccw_check_autoonline(struct ccw_device *cdev)
{
	struct ccw_dev_id id;

	ccw_device_get_id(cdev, &id);
	if (test_bit(id.devno, devs_no_auto[id.ssid]))
		return 0;
	return 1;
}

static void virtio_ccw_auto_online(void *data, async_cookie_t cookie)
{
	struct ccw_device *cdev = data;
	int ret;

	ret = ccw_device_set_online(cdev);
	if (ret)
		dev_warn(&cdev->dev, "Failed to set online: %d\n", ret);
}

static int virtio_ccw_probe(struct ccw_device *cdev)
{
	cdev->handler = virtio_ccw_int_handler;

	if (virtio_ccw_check_autoonline(cdev))
		async_schedule(virtio_ccw_auto_online, cdev);
	return 0;
}

static struct virtio_ccw_device *virtio_grab_drvdata(struct ccw_device *cdev)
{
	unsigned long flags;
	struct virtio_ccw_device *vcdev;

	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
	vcdev = dev_get_drvdata(&cdev->dev);
	if (!vcdev || vcdev->going_away) {
		spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
		return NULL;
	}
	vcdev->going_away = true;
	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
	return vcdev;
}

static void virtio_ccw_remove(struct ccw_device *cdev)
{
	unsigned long flags;
	struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);

	if (vcdev && cdev->online) {
		if (vcdev->device_lost)
			virtio_break_device(&vcdev->vdev);
		unregister_virtio_device(&vcdev->vdev);
		spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
		dev_set_drvdata(&cdev->dev, NULL);
		spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
	}
	cdev->handler = NULL;
}

static int virtio_ccw_offline(struct ccw_device *cdev)
{
	unsigned long flags;
	struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);

	if (!vcdev)
		return 0;
	if (vcdev->device_lost)
		virtio_break_device(&vcdev->vdev);
	unregister_virtio_device(&vcdev->vdev);
	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
	dev_set_drvdata(&cdev->dev, NULL);
	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
	return 0;
}

static int virtio_ccw_set_transport_rev(struct virtio_ccw_device *vcdev)
{
	struct virtio_rev_info *rev;
	struct ccw1 *ccw;
	int ret;

	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
	if (!ccw)
		return -ENOMEM;
	rev = kzalloc(sizeof(*rev), GFP_DMA | GFP_KERNEL);
	if (!rev) {
		kfree(ccw);
		return -ENOMEM;
	}

	/* Set transport revision */
	ccw->cmd_code = CCW_CMD_SET_VIRTIO_REV;
	ccw->flags = 0;
	ccw->count = sizeof(*rev);
	ccw->cda = (__u32)(unsigned long)rev;

	vcdev->revision = VIRTIO_CCW_REV_MAX;
	do {
		rev->revision = vcdev->revision;
		/* none of our supported revisions carry payload */
		rev->length = 0;
		ret = ccw_io_helper(vcdev, ccw,
				    VIRTIO_CCW_DOING_SET_VIRTIO_REV);
		if (ret == -EOPNOTSUPP) {
			if (vcdev->revision == 0)
				/*
				 * The host device does not support setting
				 * the revision: let's operate it in legacy
				 * mode.
				 */
				ret = 0;
			else
				vcdev->revision--;
		}
	} while (ret == -EOPNOTSUPP);

	kfree(ccw);
	kfree(rev);
	return ret;
}

static int virtio_ccw_online(struct ccw_device *cdev)
{
	int ret;
	struct virtio_ccw_device *vcdev;
	unsigned long flags;

	vcdev = kzalloc(sizeof(*vcdev), GFP_KERNEL);
	if (!vcdev) {
		dev_warn(&cdev->dev, "Could not get memory for virtio\n");
		ret = -ENOMEM;
		goto out_free;
	}
	vcdev->config_block = kzalloc(sizeof(*vcdev->config_block),
				   GFP_DMA | GFP_KERNEL);
	if (!vcdev->config_block) {
		ret = -ENOMEM;
		goto out_free;
	}
	vcdev->status = kzalloc(sizeof(*vcdev->status), GFP_DMA | GFP_KERNEL);
	if (!vcdev->status) {
		ret = -ENOMEM;
		goto out_free;
	}

	vcdev->is_thinint = virtio_ccw_use_airq; /* at least try */

	vcdev->vdev.dev.parent = &cdev->dev;
	vcdev->vdev.dev.release = virtio_ccw_release_dev;
	vcdev->vdev.config = &virtio_ccw_config_ops;
	vcdev->cdev = cdev;
	init_waitqueue_head(&vcdev->wait_q);
	INIT_LIST_HEAD(&vcdev->virtqueues);
	spin_lock_init(&vcdev->lock);
	mutex_init(&vcdev->io_lock);

	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
	dev_set_drvdata(&cdev->dev, vcdev);
	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
	vcdev->vdev.id.vendor = cdev->id.cu_type;
	vcdev->vdev.id.device = cdev->id.cu_model;

	ret = virtio_ccw_set_transport_rev(vcdev);
	if (ret)
		goto out_free;

	ret = register_virtio_device(&vcdev->vdev);
	if (ret) {
		dev_warn(&cdev->dev, "Failed to register virtio device: %d\n",
			 ret);
		goto out_put;
	}
	return 0;
out_put:
	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
	dev_set_drvdata(&cdev->dev, NULL);
	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
	put_device(&vcdev->vdev.dev);
	return ret;
out_free:
	if (vcdev) {
		kfree(vcdev->status);
		kfree(vcdev->config_block);
	}
	kfree(vcdev);
	return ret;
}

static int virtio_ccw_cio_notify(struct ccw_device *cdev, int event)
{
	int rc;
	struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);

	/*
	 * Make sure vcdev is set
	 * i.e. set_offline/remove callback not already running
	 */
	if (!vcdev)
		return NOTIFY_DONE;

	switch (event) {
	case CIO_GONE:
		vcdev->device_lost = true;
		rc = NOTIFY_DONE;
		break;
	case CIO_OPER:
		rc = NOTIFY_OK;
		break;
	default:
		rc = NOTIFY_DONE;
		break;
	}
	return rc;
}

static struct ccw_device_id virtio_ids[] = {
	{ CCW_DEVICE(0x3832, 0) },
	{},
};

#ifdef CONFIG_PM_SLEEP
static int virtio_ccw_freeze(struct ccw_device *cdev)
{
	struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);

	return virtio_device_freeze(&vcdev->vdev);
}

static int virtio_ccw_restore(struct ccw_device *cdev)
{
	struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
	int ret;

	ret = virtio_ccw_set_transport_rev(vcdev);
	if (ret)
		return ret;

	return virtio_device_restore(&vcdev->vdev);
}
#endif

static struct ccw_driver virtio_ccw_driver = {
	.driver = {
		.owner = THIS_MODULE,
		.name = "virtio_ccw",
	},
	.ids = virtio_ids,
	.probe = virtio_ccw_probe,
	.remove = virtio_ccw_remove,
	.set_offline = virtio_ccw_offline,
	.set_online = virtio_ccw_online,
	.notify = virtio_ccw_cio_notify,
	.int_class = IRQIO_VIR,
#ifdef CONFIG_PM_SLEEP
	.freeze = virtio_ccw_freeze,
	.thaw = virtio_ccw_restore,
	.restore = virtio_ccw_restore,
#endif
};

static int __init pure_hex(char **cp, unsigned int *val, int min_digit,
			   int max_digit, int max_val)
{
	int diff;

	diff = 0;
	*val = 0;

	while (diff <= max_digit) {
		int value = hex_to_bin(**cp);

		if (value < 0)
			break;
		*val = *val * 16 + value;
		(*cp)++;
		diff++;
	}

	if ((diff < min_digit) || (diff > max_digit) || (*val > max_val))
		return 1;

	return 0;
}

static int __init parse_busid(char *str, unsigned int *cssid,
			      unsigned int *ssid, unsigned int *devno)
{
	char *str_work;
	int rc, ret;

	rc = 1;

	if (*str == '\0')
		goto out;

	str_work = str;
	ret = pure_hex(&str_work, cssid, 1, 2, __MAX_CSSID);
	if (ret || (str_work[0] != '.'))
		goto out;
	str_work++;
	ret = pure_hex(&str_work, ssid, 1, 1, __MAX_SSID);
	if (ret || (str_work[0] != '.'))
		goto out;
	str_work++;
	ret = pure_hex(&str_work, devno, 4, 4, __MAX_SUBCHANNEL);
	if (ret || (str_work[0] != '\0'))
		goto out;

	rc = 0;
out:
	return rc;
}

static void __init no_auto_parse(void)
{
	unsigned int from_cssid, to_cssid, from_ssid, to_ssid, from, to;
	char *parm, *str;
	int rc;

	str = no_auto;
	while ((parm = strsep(&str, ","))) {
		rc = parse_busid(strsep(&parm, "-"), &from_cssid,
				 &from_ssid, &from);
		if (rc)
			continue;
		if (parm != NULL) {
			rc = parse_busid(parm, &to_cssid,
					 &to_ssid, &to);
			if ((from_ssid > to_ssid) ||
			    ((from_ssid == to_ssid) && (from > to)))
				rc = -EINVAL;
		} else {
			to_cssid = from_cssid;
			to_ssid = from_ssid;
			to = from;
		}
		if (rc)
			continue;
		while ((from_ssid < to_ssid) ||
		       ((from_ssid == to_ssid) && (from <= to))) {
			set_bit(from, devs_no_auto[from_ssid]);
			from++;
			if (from > __MAX_SUBCHANNEL) {
				from_ssid++;
				from = 0;
			}
		}
	}
}

static int __init virtio_ccw_init(void)
{
	/* parse no_auto string before we do anything further */
	no_auto_parse();
	return ccw_driver_register(&virtio_ccw_driver);
}
device_initcall(virtio_ccw_init);