1 files changed, 1090 insertions, 0 deletions

diff --git a/drivers/s390/block/dasd_eer.c b/drivers/s390/block/dasd_eer.c
new file mode 100644
index 000000000000..f70cd7716b24
--- /dev/null
+++ b/drivers/s390/block/dasd_eer.c
@@ -0,0 +1,1090 @@
+/*
+ *      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);