/*
 *	character device driver for extended error reporting
 *
 *
 *	Copyright (C) 2005 IBM Corporation
 *	extended error reporting for DASD ECKD devices
 *	Author(s): Stefan Weinhuber <wein@de.ibm.com>
 *
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/device.h>
#include <linux/workqueue.h>
#include <linux/poll.h>
#include <linux/notifier.h>

#include <asm/uaccess.h>
#include <asm/semaphore.h>
#include <asm/atomic.h>
#include <asm/ebcdic.h>

#include "dasd_int.h"
#include "dasd_eckd.h"


MODULE_LICENSE("GPL");

MODULE_AUTHOR("Stefan Weinhuber <wein@de.ibm.com>");
MODULE_DESCRIPTION("DASD extended error reporting module");


#ifdef PRINTK_HEADER
#undef PRINTK_HEADER
#endif				/* PRINTK_HEADER */
#define PRINTK_HEADER "dasd(eer):"


/*****************************************************************************/
/*      the internal buffer                                                  */
/*****************************************************************************/

/*
 * The internal buffer is meant to store obaque blobs of data, so it doesn't
 * know of higher level concepts like triggers.
 * It consists of a number of pages that are used as a ringbuffer. Each data
 * blob is stored in a simple record that consists of an integer, which
 * contains the size of the following data, and the data bytes themselfes.
 *
 * To allow for multiple independent readers we create one internal buffer
 * each time the device is opened and destroy the buffer when the file is
 * closed again.
 *
 * One record can be written to a buffer by using the functions
 * - dasd_eer_start_record (one time per record to write the size to the buffer
 *                          and reserve the space for the data)
 * - dasd_eer_write_buffer (one or more times per record to write the data)
 * The data can be written in several steps but you will have to compute
 * the total size up front for the invocation of dasd_eer_start_record.
 * If the ringbuffer is full, dasd_eer_start_record will remove the required
 * number of old records.
 *
 * A record is typically read in two steps, first read the integer that
 * specifies the size of the following data, then read the data.
 * Both can be done by
 * - dasd_eer_read_buffer
 *
 * For all mentioned functions you need to get the bufferlock first and keep it
 * until a complete record is written or read.
 */


/*
 * Alle information necessary to keep track of an internal buffer is kept in
 * a struct eerbuffer. The buffer specific to a file pointer is strored in
 * the private_data field of that file. To be able to write data to all
 * existing buffers, each buffer is also added to the bufferlist.
 * If the user doesn't want to read a complete record in one go, we have to
 * keep track of the rest of the record. residual stores the number of bytes
 * that are still to deliver. If the rest of the record is invalidated between
 * two reads then residual will be set to -1 so that the next read will fail.
 * All entries in the eerbuffer structure are protected with the bufferlock.
 * To avoid races between writing to a buffer on the one side and creating
 * and destroying buffers on the other side, the bufferlock must also be used
 * to protect the bufferlist.
 */

struct eerbuffer {
	struct list_head list;
	char **buffer;
	int buffersize;
	int buffer_page_count;
	int head;
        int tail;
	int residual;
};

LIST_HEAD(bufferlist);

static spinlock_t bufferlock = SPIN_LOCK_UNLOCKED;

DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);

/*
 * How many free bytes are available on the buffer.
 * needs to be called with bufferlock held
 */
static int
dasd_eer_get_free_bytes(struct eerbuffer *eerb)
{
	if (eerb->head < eerb->tail) {
		return eerb->tail - eerb->head - 1;
	} else
		return eerb->buffersize - eerb->head + eerb->tail -1;
}

/*
 * How many bytes of buffer space are used.
 * needs to be called with bufferlock held
 */
static int
dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
{

	if (eerb->head >= eerb->tail) {
		return eerb->head - eerb->tail;
	} else
		return eerb->buffersize - eerb->tail + eerb->head;
}

/*
 * The dasd_eer_write_buffer function just copies count bytes of data
 * to the buffer. Make sure to call dasd_eer_start_record first, to
 * make sure that enough free space is available.
 * needs to be called with bufferlock held
 */
static void
dasd_eer_write_buffer(struct eerbuffer *eerb, int count, char *data)
{

	unsigned long headindex,localhead;
	unsigned long rest, len;
	char *nextdata;

	nextdata = data;
	rest = count;
	while (rest > 0) {
 		headindex = eerb->head / PAGE_SIZE;
 		localhead = eerb->head % PAGE_SIZE;
		len = min(rest, (PAGE_SIZE - localhead));
		memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
		nextdata += len;
		rest -= len;
		eerb->head += len;
		if ( eerb->head == eerb->buffersize )
			eerb->head = 0; /* wrap around */
		if (eerb->head > eerb->buffersize) {
			MESSAGE(KERN_ERR, "%s", "runaway buffer head.");
			BUG();
		}
	}
}

/*
 * needs to be called with bufferlock held
 */
static int
dasd_eer_read_buffer(struct eerbuffer *eerb, int count, char *data)
{

	unsigned long tailindex,localtail;
	unsigned long rest, len, finalcount;
	char *nextdata;

	finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
	nextdata = data;
	rest = finalcount;
	while (rest > 0) {
 		tailindex = eerb->tail / PAGE_SIZE;
 		localtail = eerb->tail % PAGE_SIZE;
		len = min(rest, (PAGE_SIZE - localtail));
		memcpy(nextdata, eerb->buffer[tailindex]+localtail, len);
		nextdata += len;
		rest -= len;
		eerb->tail += len;
		if ( eerb->tail == eerb->buffersize )
			eerb->tail = 0; /* wrap around */
		if (eerb->tail > eerb->buffersize) {
			MESSAGE(KERN_ERR, "%s", "runaway buffer tail.");
			BUG();
		}
	}
	return finalcount;
}

/*
 * Whenever you want to write a blob of data to the internal buffer you
 * have to start by using this function first. It will write the number
 * of bytes that will be written to the buffer. If necessary it will remove
 * old records to make room for the new one.
 * needs to be called with bufferlock held
 */
static int
dasd_eer_start_record(struct eerbuffer *eerb, int count)
{
	int tailcount;
	if (count + sizeof(count) > eerb->buffersize)
		return -ENOMEM;
	while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
		if (eerb->residual > 0) {
			eerb->tail += eerb->residual;
			if (eerb->tail >= eerb->buffersize)
				eerb->tail -= eerb->buffersize;
			eerb->residual = -1;
		}
		dasd_eer_read_buffer(eerb, sizeof(tailcount),
				     (char*)(&tailcount));
		eerb->tail += tailcount;
		if (eerb->tail >= eerb->buffersize)
			eerb->tail -= eerb->buffersize;
	}
	dasd_eer_write_buffer(eerb, sizeof(count), (char*)(&count));

	return 0;
};

/*
 * release pages that are not used anymore
 */
static void
dasd_eer_free_buffer_pages(char **buf, int no_pages)
{
	int i;

	for (i = 0; i < no_pages; ++i) {
		free_page((unsigned long)buf[i]);
	}
}

/*
 * allocate a new set of memory pages
 */
static int
dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
{
	int i;

	for (i = 0; i < no_pages; ++i) {
		buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
		if (!buf[i]) {
			dasd_eer_free_buffer_pages(buf, i);
			return -ENOMEM;
		}
	}
	return 0;
}

/*
 * empty the buffer by resetting head and tail
 * In case there is a half read data blob in the buffer, we set residual
 * to -1 to indicate that the remainder of the blob is lost.
 */
static void
dasd_eer_purge_buffer(struct eerbuffer *eerb)
{
	unsigned long flags;

	spin_lock_irqsave(&bufferlock, flags);
	if (eerb->residual > 0)
		eerb->residual = -1;
	eerb->tail=0;
	eerb->head=0;
	spin_unlock_irqrestore(&bufferlock, flags);
}

/*
 * set the size of the buffer, newsize is the new number of pages to be used
 * we don't try to copy any data back an forth, so any resize will also purge
 * the buffer
 */
static int
dasd_eer_resize_buffer(struct eerbuffer *eerb, int newsize)
{
	int i, oldcount, reuse;
	char **new;
	char **old;
	unsigned long flags;

	if (newsize < 1)
		return -EINVAL;
	if (eerb->buffer_page_count == newsize) {
		/* documented behaviour is that any successfull invocation
                 * will purge all records */
		dasd_eer_purge_buffer(eerb);
		return 0;
	}
	new = kmalloc(newsize*sizeof(char*), GFP_KERNEL);
	if (!new)
		return -ENOMEM;

	reuse=min(eerb->buffer_page_count, newsize);
	for (i = 0; i < reuse; ++i) {
		new[i] = eerb->buffer[i];
	}
	if (eerb->buffer_page_count < newsize) {
		if (dasd_eer_allocate_buffer_pages(
			    &new[eerb->buffer_page_count],
			    newsize - eerb->buffer_page_count)) {
			kfree(new);
			return -ENOMEM;
		}
	}

	spin_lock_irqsave(&bufferlock, flags);
	old = eerb->buffer;
	eerb->buffer = new;
	if (eerb->residual > 0)
		eerb->residual = -1;
	eerb->tail = 0;
	eerb->head = 0;
	oldcount = eerb->buffer_page_count;
	eerb->buffer_page_count = newsize;
	spin_unlock_irqrestore(&bufferlock, flags);

	if (oldcount > newsize) {
		for (i = newsize; i < oldcount; ++i) {
			free_page((unsigned long)old[i]);
		}
	}
	kfree(old);

	return 0;
}


/*****************************************************************************/
/*      The extended error reporting functionality                           */
/*****************************************************************************/

/*
 * When a DASD device driver wants to report an error, it calls the
 * function dasd_eer_write_trigger (via a notifier mechanism) and gives the
 * respective trigger ID as parameter.
 * Currently there are four kinds of triggers:
 *
 * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
 * DASD_EER_PPRCSUSPEND: PPRC was suspended
 * DASD_EER_NOPATH:      There is no path to the device left.
 * DASD_EER_STATECHANGE: The state of the device has changed.
 *
 * For the first three triggers all required information can be supplied by
 * the caller. For these triggers a record is written by the function
 * dasd_eer_write_standard_trigger.
 *
 * When dasd_eer_write_trigger is called to write a DASD_EER_STATECHANGE
 * trigger, we have to gather the necessary sense data first. We cannot queue
 * the necessary SNSS (sense subsystem status) request immediatly, since we
 * are likely to run in a deadlock situation. Instead, we schedule a
 * work_struct that calls the function dasd_eer_sense_subsystem_status to
 * create and start an SNSS  request asynchronously.
 *
 * To avoid memory allocations at runtime, the necessary memory is allocated
 * when the extended error reporting is enabled for a device (by
 * dasd_eer_probe). There is one private eer data structure for each eer
 * enabled DASD device. It contains memory for the work_struct, one SNSS cqr
 * and a flags field that is used to coordinate the use of the cqr. The call
 * to write a state change trigger can come in at any time, so we have one flag
 * CQR_IN_USE that protects the cqr itself. When this flag indicates that the
 * cqr is currently in use, dasd_eer_sense_subsystem_status cannot start a
 * second request but sets the SNSS_REQUESTED flag instead.
 *
 * When the request is finished, the callback function dasd_eer_SNSS_cb
 * is called. This function will invoke the function
 * dasd_eer_write_SNSS_trigger to finally write the trigger. It will also
 * check the SNSS_REQUESTED flag and if it is set it will call
 * dasd_eer_sense_subsystem_status again.
 *
 * To avoid race conditions during the handling of the lock, the flags must
 * be protected by the snsslock.
 */

struct dasd_eer_private {
	struct dasd_ccw_req *cqr;
	unsigned long flags;
	struct work_struct worker;
};

static void dasd_eer_destroy(struct dasd_device *device,
			     struct dasd_eer_private *eer);
static int
dasd_eer_write_trigger(struct dasd_eer_trigger *trigger);
static void dasd_eer_sense_subsystem_status(void *data);
static int dasd_eer_notify(struct notifier_block *self,
			   unsigned long action, void *data);

struct workqueue_struct *dasd_eer_workqueue;

#define SNSS_DATA_SIZE 44
static spinlock_t snsslock = SPIN_LOCK_UNLOCKED;

#define DASD_EER_BUSID_SIZE 10
struct dasd_eer_header {
	__u32 total_size;
	__u32 trigger;
	__u64 tv_sec;
	__u64 tv_usec;
	char busid[DASD_EER_BUSID_SIZE];
} __attribute__ ((packed));

static struct notifier_block dasd_eer_nb = {
	.notifier_call = dasd_eer_notify,
};

/*
 * flags for use with dasd_eer_private
 */
#define CQR_IN_USE     0
#define SNSS_REQUESTED 1

/*
 * This function checks if extended error reporting is available for a given
 * dasd_device. If yes, then it creates and returns a struct dasd_eer,
 * otherwise it returns an -EPERM error pointer.
 */
struct dasd_eer_private *
dasd_eer_probe(struct dasd_device *device)
{
	struct dasd_eer_private *private;

	if (!(device && device->discipline
	      && !strcmp(device->discipline->name, "ECKD"))) {
		return ERR_PTR(-EPERM);
	}
	/* allocate the private data structure */
	private = (struct dasd_eer_private *)kmalloc(
		sizeof(struct dasd_eer_private), GFP_KERNEL);
	if (!private) {
		return ERR_PTR(-ENOMEM);
	}
	INIT_WORK(&private->worker, dasd_eer_sense_subsystem_status,
		  (void *)device);
	private->cqr = dasd_kmalloc_request("ECKD",
					    1 /* SNSS */ ,
					    SNSS_DATA_SIZE ,
					    device);
	if (!private->cqr) {
		kfree(private);
		return ERR_PTR(-ENOMEM);
	}
	private->flags = 0;
	return private;
};

/*
 * If our private SNSS request is queued, remove it from the
 * dasd ccw queue so we can free the requests memory.
 */
static void
dasd_eer_dequeue_SNSS_request(struct dasd_device *device,
			      struct dasd_eer_private *eer)
{
	struct list_head *lst, *nxt;
	struct dasd_ccw_req *cqr, *erpcqr;
	dasd_erp_fn_t erp_fn;

	spin_lock_irq(get_ccwdev_lock(device->cdev));
	list_for_each_safe(lst, nxt, &device->ccw_queue) {
		cqr = list_entry(lst, struct dasd_ccw_req, list);
		/* we are looking for two kinds or requests */
		/* first kind: our SNSS request: */
		if (cqr == eer->cqr) {
			if (cqr->status == DASD_CQR_IN_IO)
				device->discipline->term_IO(cqr);
			list_del(&cqr->list);
			break;
		}
		/* second kind: ERP requests for our SNSS request */
		if (cqr->refers) {
			/* If this erp request chain ends in our cqr, then */
                        /* cal the erp_postaction to clean it up  */
			erpcqr = cqr;
			while (erpcqr->refers) {
				erpcqr = erpcqr->refers;
			}
			if (erpcqr == eer->cqr) {
				erp_fn = device->discipline->erp_postaction(
					 cqr);
				erp_fn(cqr);
			}
			continue;
		}
	}
	spin_unlock_irq(get_ccwdev_lock(device->cdev));
}

/*
 * This function dismantles a struct dasd_eer that was created by
 * dasd_eer_probe. Since we want to free our private data structure,
 * we must make sure that the memory is not in use anymore.
 * We have to flush the work queue and remove a possible SNSS request
 * from the dasd queue.
 */
static void
dasd_eer_destroy(struct dasd_device *device, struct dasd_eer_private *eer)
{
	flush_workqueue(dasd_eer_workqueue);
	dasd_eer_dequeue_SNSS_request(device, eer);
	dasd_kfree_request(eer->cqr, device);
	kfree(eer);
};

/*
 * enable the extended error reporting for a particular device
 */
static int
dasd_eer_enable_on_device(struct dasd_device *device)
{
	void *eer;
	if (!device)
		return -ENODEV;
	if (device->eer)
		return 0;
	if (!try_module_get(THIS_MODULE)) {
		return -EINVAL;
	}
	eer = (void *)dasd_eer_probe(device);
	if (IS_ERR(eer)) {
		module_put(THIS_MODULE);
		return PTR_ERR(eer);
	}
	device->eer = eer;
	return 0;
}

/*
 * enable the extended error reporting for a particular device
 */
static int
dasd_eer_disable_on_device(struct dasd_device *device)
{
	struct dasd_eer_private *eer = device->eer;

	if (!device)
		return -ENODEV;
	if (!device->eer)
		return 0;
	device->eer = NULL;
	dasd_eer_destroy(device,eer);
	module_put(THIS_MODULE);

	return 0;
}

/*
 * Set extended error reporting (eer)
 * Note: This will be registered as a DASD ioctl, to be called on DASD devices.
 */
static int
dasd_ioctl_set_eer(struct block_device *bdev, int no, long args)
{
	struct dasd_device *device;
	int intval;

	if (!capable(CAP_SYS_ADMIN))
		return -EACCES;
	if (bdev != bdev->bd_contains)
		/* Error-reporting is not allowed for partitions */
		return -EINVAL;
	if (get_user(intval, (int __user *) args))
		return -EFAULT;
	device =  bdev->bd_disk->private_data;
	if (device == NULL)
		return -ENODEV;

	intval = (intval != 0);
	DEV_MESSAGE (KERN_DEBUG, device,
		     "set eer on device to %d", intval);
	if (intval)
		return dasd_eer_enable_on_device(device);
	else
		return dasd_eer_disable_on_device(device);
}

/*
 * Get value of extended error reporting.
 * Note: This will be registered as a DASD ioctl, to be called on DASD devices.
 */
static int
dasd_ioctl_get_eer(struct block_device *bdev, int no, long args)
{
	struct dasd_device *device;

	device =  bdev->bd_disk->private_data;
	if (device == NULL)
		return -ENODEV;
	return put_user((device->eer != NULL), (int __user *) args);
}

/*
 * The following function can be used for those triggers that have
 * all necessary data available when the function is called.
 * If the parameter cqr is not NULL, the chain of requests will be searched
 * for valid sense data, and all valid sense data sets will be added to
 * the triggers data.
 */
static int
dasd_eer_write_standard_trigger(int trigger, struct dasd_device *device,
				struct dasd_ccw_req *cqr)
{
	struct dasd_ccw_req *temp_cqr;
	int data_size;
	struct timeval tv;
	struct dasd_eer_header header;
	unsigned long flags;
	struct eerbuffer *eerb;

	/* go through cqr chain and count the valid sense data sets */
	temp_cqr = cqr;
	data_size = 0;
	while (temp_cqr) {
		if (temp_cqr->irb.esw.esw0.erw.cons)
			data_size += 32;
		temp_cqr = temp_cqr->refers;
	}

	header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
	header.trigger = trigger;
	do_gettimeofday(&tv);
	header.tv_sec = tv.tv_sec;
	header.tv_usec = tv.tv_usec;
	strncpy(header.busid, device->cdev->dev.bus_id, DASD_EER_BUSID_SIZE);

	spin_lock_irqsave(&bufferlock, flags);
	list_for_each_entry(eerb, &bufferlist, list) {
		dasd_eer_start_record(eerb, header.total_size);
		dasd_eer_write_buffer(eerb, sizeof(header), (char*)(&header));
		temp_cqr = cqr;
		while (temp_cqr) {
			if (temp_cqr->irb.esw.esw0.erw.cons)
				dasd_eer_write_buffer(eerb, 32, cqr->irb.ecw);
			temp_cqr = temp_cqr->refers;
		}
		dasd_eer_write_buffer(eerb, 4,"EOR");
	}
	spin_unlock_irqrestore(&bufferlock, flags);

	wake_up_interruptible(&dasd_eer_read_wait_queue);

	return 0;
}

/*
 * This function writes a DASD_EER_STATECHANGE trigger.
 */
static void
dasd_eer_write_SNSS_trigger(struct dasd_device *device,
			    struct dasd_ccw_req *cqr)
{
	int data_size;
	int snss_rc;
	struct timeval tv;
	struct dasd_eer_header header;
	unsigned long flags;
	struct eerbuffer *eerb;

	snss_rc = (cqr->status == DASD_CQR_FAILED) ? -EIO : 0;
	if (snss_rc)
		data_size = 0;
	else
		data_size = SNSS_DATA_SIZE;

	header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
	header.trigger = DASD_EER_STATECHANGE;
	do_gettimeofday(&tv);
	header.tv_sec = tv.tv_sec;
	header.tv_usec = tv.tv_usec;
	strncpy(header.busid, device->cdev->dev.bus_id, DASD_EER_BUSID_SIZE);

	spin_lock_irqsave(&bufferlock, flags);
	list_for_each_entry(eerb, &bufferlist, list) {
		dasd_eer_start_record(eerb, header.total_size);
		dasd_eer_write_buffer(eerb, sizeof(header),(char*)(&header));
		if (!snss_rc)
			dasd_eer_write_buffer(eerb, SNSS_DATA_SIZE, cqr->data);
		dasd_eer_write_buffer(eerb, 4,"EOR");
	}
	spin_unlock_irqrestore(&bufferlock, flags);

	wake_up_interruptible(&dasd_eer_read_wait_queue);
}

/*
 * callback function for use with SNSS request
 */
static void
dasd_eer_SNSS_cb(struct dasd_ccw_req *cqr, void *data)
{
        struct dasd_device *device;
	struct dasd_eer_private *private;
	unsigned long irqflags;

        device = (struct dasd_device *)data;
	private = (struct dasd_eer_private *)device->eer;
	dasd_eer_write_SNSS_trigger(device, cqr);
	spin_lock_irqsave(&snsslock, irqflags);
	if(!test_and_clear_bit(SNSS_REQUESTED, &private->flags)) {
		clear_bit(CQR_IN_USE, &private->flags);
		spin_unlock_irqrestore(&snsslock, irqflags);
		return;
	};
	clear_bit(CQR_IN_USE, &private->flags);
	spin_unlock_irqrestore(&snsslock, irqflags);
	dasd_eer_sense_subsystem_status(device);
	return;
}

/*
 * clean a used cqr before using it again
 */
static void
dasd_eer_clean_SNSS_request(struct dasd_ccw_req *cqr)
{
	struct ccw1 *cpaddr = cqr->cpaddr;
	void *data = cqr->data;

	memset(cqr, 0, sizeof(struct dasd_ccw_req));
	memset(cpaddr, 0, sizeof(struct ccw1));
	memset(data, 0, SNSS_DATA_SIZE);
	cqr->cpaddr = cpaddr;
	cqr->data = data;
	strncpy((char *) &cqr->magic, "ECKD", 4);
	ASCEBC((char *) &cqr->magic, 4);
	set_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
}

/*
 * build and start an SNSS request
 * This function is called from a work queue so we have to
 * pass the dasd_device pointer as a void pointer.
 */
static void
dasd_eer_sense_subsystem_status(void *data)
{
	struct dasd_device *device;
	struct dasd_eer_private *private;
	struct dasd_ccw_req *cqr;
	struct ccw1 *ccw;
	unsigned long irqflags;

	device = (struct dasd_device *)data;
	private = (struct dasd_eer_private *)device->eer;
	if (!private) /* device not eer enabled any more */
		return;
	cqr = private->cqr;
	spin_lock_irqsave(&snsslock, irqflags);
	if(test_and_set_bit(CQR_IN_USE, &private->flags)) {
		set_bit(SNSS_REQUESTED, &private->flags);
		spin_unlock_irqrestore(&snsslock, irqflags);
		return;
	};
	spin_unlock_irqrestore(&snsslock, irqflags);
	dasd_eer_clean_SNSS_request(cqr);
	cqr->device = device;
	cqr->retries = 255;
	cqr->expires = 10 * HZ;

	ccw = cqr->cpaddr;
	ccw->cmd_code = DASD_ECKD_CCW_SNSS;
	ccw->count = SNSS_DATA_SIZE;
	ccw->flags = 0;
	ccw->cda = (__u32)(addr_t)cqr->data;

	cqr->buildclk = get_clock();
	cqr->status = DASD_CQR_FILLED;
	cqr->callback = dasd_eer_SNSS_cb;
	cqr->callback_data = (void *)device;
        dasd_add_request_head(cqr);

	return;
}

/*
 * This function is called for all triggers. It calls the appropriate
 * function that writes the actual trigger records.
 */
static int
dasd_eer_write_trigger(struct dasd_eer_trigger *trigger)
{
	int rc;
	struct dasd_eer_private *private = trigger->device->eer;

	switch (trigger->id) {
	case DASD_EER_FATALERROR:
	case DASD_EER_PPRCSUSPEND:
		rc = dasd_eer_write_standard_trigger(
			trigger->id, trigger->device, trigger->cqr);
		break;
	case DASD_EER_NOPATH:
		rc = dasd_eer_write_standard_trigger(
			trigger->id, trigger->device, NULL);
		break;
	case DASD_EER_STATECHANGE:
                if (queue_work(dasd_eer_workqueue, &private->worker)) {
                        rc=0;
                } else {
                        /* If the work_struct was already queued, it can't
                         * be queued again. But this is OK since we don't
                         * need to have it queued twice.
                         */
                        rc = -EBUSY;
                }
		break;
	default: /* unknown trigger, so we write it without any sense data */
		rc = dasd_eer_write_standard_trigger(
			trigger->id, trigger->device, NULL);
		break;
	}
	return rc;
}

/*
 * This function is registered with the dasd device driver and gets called
 * for all dasd eer notifications.
 */
static int dasd_eer_notify(struct notifier_block *self,
			    unsigned long action, void *data)
{
	switch (action) {
	case DASD_EER_DISABLE:
		dasd_eer_disable_on_device((struct dasd_device *)data);
		break;
	case DASD_EER_TRIGGER:
		dasd_eer_write_trigger((struct dasd_eer_trigger *)data);
		break;
	}
	return NOTIFY_OK;
}


/*****************************************************************************/
/*      the device operations                                                */
/*****************************************************************************/

/*
 * On the one side we need a lock to access our internal buffer, on the
 * other side a copy_to_user can sleep. So we need to copy the data we have
 * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
 */
static char readbuffer[PAGE_SIZE];
DECLARE_MUTEX(readbuffer_mutex);


static int
dasd_eer_open(struct inode *inp, struct file *filp)
{
	struct eerbuffer *eerb;
	unsigned long flags;

	eerb = kmalloc(sizeof(struct eerbuffer), GFP_KERNEL);
	eerb->head = 0;
	eerb->tail = 0;
	eerb->residual = 0;
	eerb->buffer_page_count = 1;
	eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
        eerb->buffer = kmalloc(eerb->buffer_page_count*sizeof(char*),
			       GFP_KERNEL);
        if (!eerb->buffer)
                return -ENOMEM;
	if (dasd_eer_allocate_buffer_pages(eerb->buffer,
					   eerb->buffer_page_count)) {
		kfree(eerb->buffer);
		return -ENOMEM;
	}
	filp->private_data = eerb;
	spin_lock_irqsave(&bufferlock, flags);
	list_add(&eerb->list, &bufferlist);
	spin_unlock_irqrestore(&bufferlock, flags);

	return nonseekable_open(inp,filp);
}

static int
dasd_eer_close(struct inode *inp, struct file *filp)
{
	struct eerbuffer *eerb;
	unsigned long flags;

	eerb = (struct eerbuffer *)filp->private_data;
	spin_lock_irqsave(&bufferlock, flags);
	list_del(&eerb->list);
	spin_unlock_irqrestore(&bufferlock, flags);
	dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
	kfree(eerb->buffer);
	kfree(eerb);

	return 0;
}

static long
dasd_eer_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	int intval;
	struct eerbuffer *eerb;

	eerb = (struct eerbuffer *)filp->private_data;
	switch (cmd) {
	case DASD_EER_PURGE:
		dasd_eer_purge_buffer(eerb);
		return 0;
	case DASD_EER_SETBUFSIZE:
		if (get_user(intval, (int __user *)arg))
			return -EFAULT;
		return dasd_eer_resize_buffer(eerb, intval);
	default:
		return -ENOIOCTLCMD;
	}
}

static ssize_t
dasd_eer_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
{
	int tc,rc;
	int tailcount,effective_count;
        unsigned long flags;
	struct eerbuffer *eerb;

	eerb = (struct eerbuffer *)filp->private_data;
	if(down_interruptible(&readbuffer_mutex))
		return -ERESTARTSYS;

	spin_lock_irqsave(&bufferlock, flags);

	if (eerb->residual < 0) { /* the remainder of this record */
		                  /* has been deleted             */
		eerb->residual = 0;
		spin_unlock_irqrestore(&bufferlock, flags);
		up(&readbuffer_mutex);
		return -EIO;
	} else if (eerb->residual > 0) {
		/* OK we still have a second half of a record to deliver */
		effective_count = min(eerb->residual, (int)count);
		eerb->residual -= effective_count;
	} else {
		tc = 0;
		while (!tc) {
			tc = dasd_eer_read_buffer(eerb,
				sizeof(tailcount), (char*)(&tailcount));
			if (!tc) {
				/* no data available */
				spin_unlock_irqrestore(&bufferlock, flags);
				up(&readbuffer_mutex);
				if (filp->f_flags & O_NONBLOCK)
					return -EAGAIN;
				rc = wait_event_interruptible(
					dasd_eer_read_wait_queue,
					eerb->head != eerb->tail);
				if (rc) {
					return rc;
				}
				if(down_interruptible(&readbuffer_mutex))
					return -ERESTARTSYS;
				spin_lock_irqsave(&bufferlock, flags);
			}
		}
		WARN_ON(tc != sizeof(tailcount));
		effective_count = min(tailcount,(int)count);
		eerb->residual = tailcount - effective_count;
	}

	tc = dasd_eer_read_buffer(eerb, effective_count, readbuffer);
	WARN_ON(tc != effective_count);

	spin_unlock_irqrestore(&bufferlock, flags);

	if (copy_to_user(buf, readbuffer, effective_count)) {
		up(&readbuffer_mutex);
		return -EFAULT;
	}

	up(&readbuffer_mutex);
	return effective_count;
}

static unsigned int
dasd_eer_poll (struct file *filp, poll_table *ptable)
{
	unsigned int mask;
	unsigned long flags;
	struct eerbuffer *eerb;

	eerb = (struct eerbuffer *)filp->private_data;
	poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
	spin_lock_irqsave(&bufferlock, flags);
	if (eerb->head != eerb->tail)
		mask = POLLIN | POLLRDNORM ;
	else
		mask = 0;
	spin_unlock_irqrestore(&bufferlock, flags);
	return mask;
}

static struct file_operations dasd_eer_fops = {
	.open		= &dasd_eer_open,
	.release	= &dasd_eer_close,
	.unlocked_ioctl = &dasd_eer_ioctl,
	.compat_ioctl	= &dasd_eer_ioctl,
	.read		= &dasd_eer_read,
	.poll		= &dasd_eer_poll,
	.owner		= THIS_MODULE,
};

static struct miscdevice dasd_eer_dev = {
	.minor	    = MISC_DYNAMIC_MINOR,
	.name	    = "dasd_eer",
	.fops	    = &dasd_eer_fops,
};


/*****************************************************************************/
/*	Init and exit							     */
/*****************************************************************************/

static int
__init dasd_eer_init(void)
{
	int rc;

	dasd_eer_workqueue = create_singlethread_workqueue("dasd_eer");
	if (!dasd_eer_workqueue) {
		MESSAGE(KERN_ERR , "%s", "dasd_eer_init could not "
		       "create workqueue \n");
		rc = -ENOMEM;
		goto out;
	}

	rc = dasd_register_eer_notifier(&dasd_eer_nb);
	if (rc) {
		MESSAGE(KERN_ERR, "%s", "dasd_eer_init could not "
		       "register error reporting");
		goto queue;
	}

	dasd_ioctl_no_register(THIS_MODULE, BIODASDEERSET, dasd_ioctl_set_eer);
	dasd_ioctl_no_register(THIS_MODULE, BIODASDEERGET, dasd_ioctl_get_eer);

	/* we don't need our own character device,
	 * so we just register as misc device */
	rc = misc_register(&dasd_eer_dev);
	if (rc) {
		MESSAGE(KERN_ERR, "%s", "dasd_eer_init could not "
		       "register misc device");
		goto unregister;
	}

	return 0;

unregister:
	dasd_unregister_eer_notifier(&dasd_eer_nb);
	dasd_ioctl_no_unregister(THIS_MODULE, BIODASDEERSET,
				 dasd_ioctl_set_eer);
	dasd_ioctl_no_unregister(THIS_MODULE, BIODASDEERGET,
				 dasd_ioctl_get_eer);
queue:
	destroy_workqueue(dasd_eer_workqueue);
out:
	return rc;

}
module_init(dasd_eer_init);

static void
__exit dasd_eer_exit(void)
{
	dasd_unregister_eer_notifier(&dasd_eer_nb);
	dasd_ioctl_no_unregister(THIS_MODULE, BIODASDEERSET,
				 dasd_ioctl_set_eer);
	dasd_ioctl_no_unregister(THIS_MODULE, BIODASDEERGET,
				 dasd_ioctl_get_eer);
	destroy_workqueue(dasd_eer_workqueue);

	WARN_ON(misc_deregister(&dasd_eer_dev) != 0);
}
module_exit(dasd_eer_exit);