linux/drivers/s390/block/dasd_eer.c
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   1/*
   2 *  Character device driver for extended error reporting.
   3 *
   4 *  Copyright (C) 2005 IBM Corporation
   5 *  extended error reporting for DASD ECKD devices
   6 *  Author(s): Stefan Weinhuber <wein@de.ibm.com>
   7 */
   8
   9#define KMSG_COMPONENT "dasd-eckd"
  10
  11#include <linux/init.h>
  12#include <linux/fs.h>
  13#include <linux/kernel.h>
  14#include <linux/miscdevice.h>
  15#include <linux/module.h>
  16#include <linux/moduleparam.h>
  17#include <linux/device.h>
  18#include <linux/poll.h>
  19#include <linux/mutex.h>
  20#include <linux/err.h>
  21#include <linux/slab.h>
  22
  23#include <asm/uaccess.h>
  24#include <asm/atomic.h>
  25#include <asm/ebcdic.h>
  26
  27#include "dasd_int.h"
  28#include "dasd_eckd.h"
  29
  30#ifdef PRINTK_HEADER
  31#undef PRINTK_HEADER
  32#endif                          /* PRINTK_HEADER */
  33#define PRINTK_HEADER "dasd(eer):"
  34
  35/*
  36 * SECTION: the internal buffer
  37 */
  38
  39/*
  40 * The internal buffer is meant to store obaque blobs of data, so it does
  41 * not know of higher level concepts like triggers.
  42 * It consists of a number of pages that are used as a ringbuffer. Each data
  43 * blob is stored in a simple record that consists of an integer, which
  44 * contains the size of the following data, and the data bytes themselfes.
  45 *
  46 * To allow for multiple independent readers we create one internal buffer
  47 * each time the device is opened and destroy the buffer when the file is
  48 * closed again. The number of pages used for this buffer is determined by
  49 * the module parmeter eer_pages.
  50 *
  51 * One record can be written to a buffer by using the functions
  52 * - dasd_eer_start_record (one time per record to write the size to the
  53 *                          buffer and reserve the space for the data)
  54 * - dasd_eer_write_buffer (one or more times per record to write the data)
  55 * The data can be written in several steps but you will have to compute
  56 * the total size up front for the invocation of dasd_eer_start_record.
  57 * If the ringbuffer is full, dasd_eer_start_record will remove the required
  58 * number of old records.
  59 *
  60 * A record is typically read in two steps, first read the integer that
  61 * specifies the size of the following data, then read the data.
  62 * Both can be done by
  63 * - dasd_eer_read_buffer
  64 *
  65 * For all mentioned functions you need to get the bufferlock first and keep
  66 * it until a complete record is written or read.
  67 *
  68 * All information necessary to keep track of an internal buffer is kept in
  69 * a struct eerbuffer. The buffer specific to a file pointer is strored in
  70 * the private_data field of that file. To be able to write data to all
  71 * existing buffers, each buffer is also added to the bufferlist.
  72 * If the user does not want to read a complete record in one go, we have to
  73 * keep track of the rest of the record. residual stores the number of bytes
  74 * that are still to deliver. If the rest of the record is invalidated between
  75 * two reads then residual will be set to -1 so that the next read will fail.
  76 * All entries in the eerbuffer structure are protected with the bufferlock.
  77 * To avoid races between writing to a buffer on the one side and creating
  78 * and destroying buffers on the other side, the bufferlock must also be used
  79 * to protect the bufferlist.
  80 */
  81
  82static int eer_pages = 5;
  83module_param(eer_pages, int, S_IRUGO|S_IWUSR);
  84
  85struct eerbuffer {
  86        struct list_head list;
  87        char **buffer;
  88        int buffersize;
  89        int buffer_page_count;
  90        int head;
  91        int tail;
  92        int residual;
  93};
  94
  95static LIST_HEAD(bufferlist);
  96static DEFINE_SPINLOCK(bufferlock);
  97static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
  98
  99/*
 100 * How many free bytes are available on the buffer.
 101 * Needs to be called with bufferlock held.
 102 */
 103static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
 104{
 105        if (eerb->head < eerb->tail)
 106                return eerb->tail - eerb->head - 1;
 107        return eerb->buffersize - eerb->head + eerb->tail -1;
 108}
 109
 110/*
 111 * How many bytes of buffer space are used.
 112 * Needs to be called with bufferlock held.
 113 */
 114static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
 115{
 116
 117        if (eerb->head >= eerb->tail)
 118                return eerb->head - eerb->tail;
 119        return eerb->buffersize - eerb->tail + eerb->head;
 120}
 121
 122/*
 123 * The dasd_eer_write_buffer function just copies count bytes of data
 124 * to the buffer. Make sure to call dasd_eer_start_record first, to
 125 * make sure that enough free space is available.
 126 * Needs to be called with bufferlock held.
 127 */
 128static void dasd_eer_write_buffer(struct eerbuffer *eerb,
 129                                  char *data, int count)
 130{
 131
 132        unsigned long headindex,localhead;
 133        unsigned long rest, len;
 134        char *nextdata;
 135
 136        nextdata = data;
 137        rest = count;
 138        while (rest > 0) {
 139                headindex = eerb->head / PAGE_SIZE;
 140                localhead = eerb->head % PAGE_SIZE;
 141                len = min(rest, PAGE_SIZE - localhead);
 142                memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
 143                nextdata += len;
 144                rest -= len;
 145                eerb->head += len;
 146                if (eerb->head == eerb->buffersize)
 147                        eerb->head = 0; /* wrap around */
 148                BUG_ON(eerb->head > eerb->buffersize);
 149        }
 150}
 151
 152/*
 153 * Needs to be called with bufferlock held.
 154 */
 155static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
 156{
 157
 158        unsigned long tailindex,localtail;
 159        unsigned long rest, len, finalcount;
 160        char *nextdata;
 161
 162        finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
 163        nextdata = data;
 164        rest = finalcount;
 165        while (rest > 0) {
 166                tailindex = eerb->tail / PAGE_SIZE;
 167                localtail = eerb->tail % PAGE_SIZE;
 168                len = min(rest, PAGE_SIZE - localtail);
 169                memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
 170                nextdata += len;
 171                rest -= len;
 172                eerb->tail += len;
 173                if (eerb->tail == eerb->buffersize)
 174                        eerb->tail = 0; /* wrap around */
 175                BUG_ON(eerb->tail > eerb->buffersize);
 176        }
 177        return finalcount;
 178}
 179
 180/*
 181 * Whenever you want to write a blob of data to the internal buffer you
 182 * have to start by using this function first. It will write the number
 183 * of bytes that will be written to the buffer. If necessary it will remove
 184 * old records to make room for the new one.
 185 * Needs to be called with bufferlock held.
 186 */
 187static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
 188{
 189        int tailcount;
 190
 191        if (count + sizeof(count) > eerb->buffersize)
 192                return -ENOMEM;
 193        while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
 194                if (eerb->residual > 0) {
 195                        eerb->tail += eerb->residual;
 196                        if (eerb->tail >= eerb->buffersize)
 197                                eerb->tail -= eerb->buffersize;
 198                        eerb->residual = -1;
 199                }
 200                dasd_eer_read_buffer(eerb, (char *) &tailcount,
 201                                     sizeof(tailcount));
 202                eerb->tail += tailcount;
 203                if (eerb->tail >= eerb->buffersize)
 204                        eerb->tail -= eerb->buffersize;
 205        }
 206        dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
 207
 208        return 0;
 209};
 210
 211/*
 212 * Release pages that are not used anymore.
 213 */
 214static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
 215{
 216        int i;
 217
 218        for (i = 0; i < no_pages; i++)
 219                free_page((unsigned long) buf[i]);
 220}
 221
 222/*
 223 * Allocate a new set of memory pages.
 224 */
 225static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
 226{
 227        int i;
 228
 229        for (i = 0; i < no_pages; i++) {
 230                buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
 231                if (!buf[i]) {
 232                        dasd_eer_free_buffer_pages(buf, i);
 233                        return -ENOMEM;
 234                }
 235        }
 236        return 0;
 237}
 238
 239/*
 240 * SECTION: The extended error reporting functionality
 241 */
 242
 243/*
 244 * When a DASD device driver wants to report an error, it calls the
 245 * function dasd_eer_write and gives the respective trigger ID as
 246 * parameter. Currently there are four kinds of triggers:
 247 *
 248 * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
 249 * DASD_EER_PPRCSUSPEND: PPRC was suspended
 250 * DASD_EER_NOPATH:      There is no path to the device left.
 251 * DASD_EER_STATECHANGE: The state of the device has changed.
 252 *
 253 * For the first three triggers all required information can be supplied by
 254 * the caller. For these triggers a record is written by the function
 255 * dasd_eer_write_standard_trigger.
 256 *
 257 * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
 258 * status ccw need to be executed to gather the necessary sense data first.
 259 * The dasd_eer_snss function will queue the SNSS request and the request
 260 * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
 261 * trigger.
 262 *
 263 * To avoid memory allocations at runtime, the necessary memory is allocated
 264 * when the extended error reporting is enabled for a device (by
 265 * dasd_eer_probe). There is one sense subsystem status request for each
 266 * eer enabled DASD device. The presence of the cqr in device->eer_cqr
 267 * indicates that eer is enable for the device. The use of the snss request
 268 * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
 269 * that the cqr is currently in use, dasd_eer_snss cannot start a second
 270 * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
 271 * the SNSS request will check the bit and call dasd_eer_snss again.
 272 */
 273
 274#define SNSS_DATA_SIZE 44
 275
 276#define DASD_EER_BUSID_SIZE 10
 277struct dasd_eer_header {
 278        __u32 total_size;
 279        __u32 trigger;
 280        __u64 tv_sec;
 281        __u64 tv_usec;
 282        char busid[DASD_EER_BUSID_SIZE];
 283} __attribute__ ((packed));
 284
 285/*
 286 * The following function can be used for those triggers that have
 287 * all necessary data available when the function is called.
 288 * If the parameter cqr is not NULL, the chain of requests will be searched
 289 * for valid sense data, and all valid sense data sets will be added to
 290 * the triggers data.
 291 */
 292static void dasd_eer_write_standard_trigger(struct dasd_device *device,
 293                                            struct dasd_ccw_req *cqr,
 294                                            int trigger)
 295{
 296        struct dasd_ccw_req *temp_cqr;
 297        int data_size;
 298        struct timeval tv;
 299        struct dasd_eer_header header;
 300        unsigned long flags;
 301        struct eerbuffer *eerb;
 302        char *sense;
 303
 304        /* go through cqr chain and count the valid sense data sets */
 305        data_size = 0;
 306        for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
 307                if (dasd_get_sense(&temp_cqr->irb))
 308                        data_size += 32;
 309
 310        header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 311        header.trigger = trigger;
 312        do_gettimeofday(&tv);
 313        header.tv_sec = tv.tv_sec;
 314        header.tv_usec = tv.tv_usec;
 315        strncpy(header.busid, dev_name(&device->cdev->dev),
 316                DASD_EER_BUSID_SIZE);
 317
 318        spin_lock_irqsave(&bufferlock, flags);
 319        list_for_each_entry(eerb, &bufferlist, list) {
 320                dasd_eer_start_record(eerb, header.total_size);
 321                dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
 322                for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers) {
 323                        sense = dasd_get_sense(&temp_cqr->irb);
 324                        if (sense)
 325                                dasd_eer_write_buffer(eerb, sense, 32);
 326                }
 327                dasd_eer_write_buffer(eerb, "EOR", 4);
 328        }
 329        spin_unlock_irqrestore(&bufferlock, flags);
 330        wake_up_interruptible(&dasd_eer_read_wait_queue);
 331}
 332
 333/*
 334 * This function writes a DASD_EER_STATECHANGE trigger.
 335 */
 336static void dasd_eer_write_snss_trigger(struct dasd_device *device,
 337                                        struct dasd_ccw_req *cqr,
 338                                        int trigger)
 339{
 340        int data_size;
 341        int snss_rc;
 342        struct timeval tv;
 343        struct dasd_eer_header header;
 344        unsigned long flags;
 345        struct eerbuffer *eerb;
 346
 347        snss_rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
 348        if (snss_rc)
 349                data_size = 0;
 350        else
 351                data_size = SNSS_DATA_SIZE;
 352
 353        header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 354        header.trigger = DASD_EER_STATECHANGE;
 355        do_gettimeofday(&tv);
 356        header.tv_sec = tv.tv_sec;
 357        header.tv_usec = tv.tv_usec;
 358        strncpy(header.busid, dev_name(&device->cdev->dev),
 359                DASD_EER_BUSID_SIZE);
 360
 361        spin_lock_irqsave(&bufferlock, flags);
 362        list_for_each_entry(eerb, &bufferlist, list) {
 363                dasd_eer_start_record(eerb, header.total_size);
 364                dasd_eer_write_buffer(eerb, (char *) &header , sizeof(header));
 365                if (!snss_rc)
 366                        dasd_eer_write_buffer(eerb, cqr->data, SNSS_DATA_SIZE);
 367                dasd_eer_write_buffer(eerb, "EOR", 4);
 368        }
 369        spin_unlock_irqrestore(&bufferlock, flags);
 370        wake_up_interruptible(&dasd_eer_read_wait_queue);
 371}
 372
 373/*
 374 * This function is called for all triggers. It calls the appropriate
 375 * function that writes the actual trigger records.
 376 */
 377void dasd_eer_write(struct dasd_device *device, struct dasd_ccw_req *cqr,
 378                    unsigned int id)
 379{
 380        if (!device->eer_cqr)
 381                return;
 382        switch (id) {
 383        case DASD_EER_FATALERROR:
 384        case DASD_EER_PPRCSUSPEND:
 385                dasd_eer_write_standard_trigger(device, cqr, id);
 386                break;
 387        case DASD_EER_NOPATH:
 388                dasd_eer_write_standard_trigger(device, NULL, id);
 389                break;
 390        case DASD_EER_STATECHANGE:
 391                dasd_eer_write_snss_trigger(device, cqr, id);
 392                break;
 393        default: /* unknown trigger, so we write it without any sense data */
 394                dasd_eer_write_standard_trigger(device, NULL, id);
 395                break;
 396        }
 397}
 398EXPORT_SYMBOL(dasd_eer_write);
 399
 400/*
 401 * Start a sense subsystem status request.
 402 * Needs to be called with the device held.
 403 */
 404void dasd_eer_snss(struct dasd_device *device)
 405{
 406        struct dasd_ccw_req *cqr;
 407
 408        cqr = device->eer_cqr;
 409        if (!cqr)       /* Device not eer enabled. */
 410                return;
 411        if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
 412                /* Sense subsystem status request in use. */
 413                set_bit(DASD_FLAG_EER_SNSS, &device->flags);
 414                return;
 415        }
 416        /* cdev is already locked, can't use dasd_add_request_head */
 417        clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 418        cqr->status = DASD_CQR_QUEUED;
 419        list_add(&cqr->devlist, &device->ccw_queue);
 420        dasd_schedule_device_bh(device);
 421}
 422
 423/*
 424 * Callback function for use with sense subsystem status request.
 425 */
 426static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
 427{
 428        struct dasd_device *device = cqr->startdev;
 429        unsigned long flags;
 430
 431        dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
 432        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 433        if (device->eer_cqr == cqr) {
 434                clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 435                if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
 436                        /* Another SNSS has been requested in the meantime. */
 437                        dasd_eer_snss(device);
 438                cqr = NULL;
 439        }
 440        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 441        if (cqr)
 442                /*
 443                 * Extended error recovery has been switched off while
 444                 * the SNSS request was running. It could even have
 445                 * been switched off and on again in which case there
 446                 * is a new ccw in device->eer_cqr. Free the "old"
 447                 * snss request now.
 448                 */
 449                dasd_kfree_request(cqr, device);
 450}
 451
 452/*
 453 * Enable error reporting on a given device.
 454 */
 455int dasd_eer_enable(struct dasd_device *device)
 456{
 457        struct dasd_ccw_req *cqr;
 458        unsigned long flags;
 459        struct ccw1 *ccw;
 460
 461        if (device->eer_cqr)
 462                return 0;
 463
 464        if (!device->discipline || strcmp(device->discipline->name, "ECKD"))
 465                return -EPERM;  /* FIXME: -EMEDIUMTYPE ? */
 466
 467        cqr = dasd_kmalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
 468                                   SNSS_DATA_SIZE, device);
 469        if (IS_ERR(cqr))
 470                return -ENOMEM;
 471
 472        cqr->startdev = device;
 473        cqr->retries = 255;
 474        cqr->expires = 10 * HZ;
 475        clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
 476        set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
 477
 478        ccw = cqr->cpaddr;
 479        ccw->cmd_code = DASD_ECKD_CCW_SNSS;
 480        ccw->count = SNSS_DATA_SIZE;
 481        ccw->flags = 0;
 482        ccw->cda = (__u32)(addr_t) cqr->data;
 483
 484        cqr->buildclk = get_clock();
 485        cqr->status = DASD_CQR_FILLED;
 486        cqr->callback = dasd_eer_snss_cb;
 487
 488        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 489        if (!device->eer_cqr) {
 490                device->eer_cqr = cqr;
 491                cqr = NULL;
 492        }
 493        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 494        if (cqr)
 495                dasd_kfree_request(cqr, device);
 496        return 0;
 497}
 498
 499/*
 500 * Disable error reporting on a given device.
 501 */
 502void dasd_eer_disable(struct dasd_device *device)
 503{
 504        struct dasd_ccw_req *cqr;
 505        unsigned long flags;
 506        int in_use;
 507
 508        if (!device->eer_cqr)
 509                return;
 510        spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 511        cqr = device->eer_cqr;
 512        device->eer_cqr = NULL;
 513        clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 514        in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 515        spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 516        if (cqr && !in_use)
 517                dasd_kfree_request(cqr, device);
 518}
 519
 520/*
 521 * SECTION: the device operations
 522 */
 523
 524/*
 525 * On the one side we need a lock to access our internal buffer, on the
 526 * other side a copy_to_user can sleep. So we need to copy the data we have
 527 * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
 528 */
 529static char readbuffer[PAGE_SIZE];
 530static DEFINE_MUTEX(readbuffer_mutex);
 531
 532static int dasd_eer_open(struct inode *inp, struct file *filp)
 533{
 534        struct eerbuffer *eerb;
 535        unsigned long flags;
 536
 537        eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
 538        if (!eerb)
 539                return -ENOMEM;
 540        eerb->buffer_page_count = eer_pages;
 541        if (eerb->buffer_page_count < 1 ||
 542            eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
 543                kfree(eerb);
 544                DBF_EVENT(DBF_WARNING, "can't open device since module "
 545                        "parameter eer_pages is smaller than 1 or"
 546                        " bigger than %d", (int)(INT_MAX / PAGE_SIZE));
 547                return -EINVAL;
 548        }
 549        eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
 550        eerb->buffer = kmalloc(eerb->buffer_page_count * sizeof(char *),
 551                               GFP_KERNEL);
 552        if (!eerb->buffer) {
 553                kfree(eerb);
 554                return -ENOMEM;
 555        }
 556        if (dasd_eer_allocate_buffer_pages(eerb->buffer,
 557                                           eerb->buffer_page_count)) {
 558                kfree(eerb->buffer);
 559                kfree(eerb);
 560                return -ENOMEM;
 561        }
 562        filp->private_data = eerb;
 563        spin_lock_irqsave(&bufferlock, flags);
 564        list_add(&eerb->list, &bufferlist);
 565        spin_unlock_irqrestore(&bufferlock, flags);
 566
 567        return nonseekable_open(inp,filp);
 568}
 569
 570static int dasd_eer_close(struct inode *inp, struct file *filp)
 571{
 572        struct eerbuffer *eerb;
 573        unsigned long flags;
 574
 575        eerb = (struct eerbuffer *) filp->private_data;
 576        spin_lock_irqsave(&bufferlock, flags);
 577        list_del(&eerb->list);
 578        spin_unlock_irqrestore(&bufferlock, flags);
 579        dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
 580        kfree(eerb->buffer);
 581        kfree(eerb);
 582
 583        return 0;
 584}
 585
 586static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
 587                             size_t count, loff_t *ppos)
 588{
 589        int tc,rc;
 590        int tailcount,effective_count;
 591        unsigned long flags;
 592        struct eerbuffer *eerb;
 593
 594        eerb = (struct eerbuffer *) filp->private_data;
 595        if (mutex_lock_interruptible(&readbuffer_mutex))
 596                return -ERESTARTSYS;
 597
 598        spin_lock_irqsave(&bufferlock, flags);
 599
 600        if (eerb->residual < 0) { /* the remainder of this record */
 601                                  /* has been deleted             */
 602                eerb->residual = 0;
 603                spin_unlock_irqrestore(&bufferlock, flags);
 604                mutex_unlock(&readbuffer_mutex);
 605                return -EIO;
 606        } else if (eerb->residual > 0) {
 607                /* OK we still have a second half of a record to deliver */
 608                effective_count = min(eerb->residual, (int) count);
 609                eerb->residual -= effective_count;
 610        } else {
 611                tc = 0;
 612                while (!tc) {
 613                        tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
 614                                                  sizeof(tailcount));
 615                        if (!tc) {
 616                                /* no data available */
 617                                spin_unlock_irqrestore(&bufferlock, flags);
 618                                mutex_unlock(&readbuffer_mutex);
 619                                if (filp->f_flags & O_NONBLOCK)
 620                                        return -EAGAIN;
 621                                rc = wait_event_interruptible(
 622                                        dasd_eer_read_wait_queue,
 623                                        eerb->head != eerb->tail);
 624                                if (rc)
 625                                        return rc;
 626                                if (mutex_lock_interruptible(&readbuffer_mutex))
 627                                        return -ERESTARTSYS;
 628                                spin_lock_irqsave(&bufferlock, flags);
 629                        }
 630                }
 631                WARN_ON(tc != sizeof(tailcount));
 632                effective_count = min(tailcount,(int)count);
 633                eerb->residual = tailcount - effective_count;
 634        }
 635
 636        tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
 637        WARN_ON(tc != effective_count);
 638
 639        spin_unlock_irqrestore(&bufferlock, flags);
 640
 641        if (copy_to_user(buf, readbuffer, effective_count)) {
 642                mutex_unlock(&readbuffer_mutex);
 643                return -EFAULT;
 644        }
 645
 646        mutex_unlock(&readbuffer_mutex);
 647        return effective_count;
 648}
 649
 650static unsigned int dasd_eer_poll(struct file *filp, poll_table *ptable)
 651{
 652        unsigned int mask;
 653        unsigned long flags;
 654        struct eerbuffer *eerb;
 655
 656        eerb = (struct eerbuffer *) filp->private_data;
 657        poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
 658        spin_lock_irqsave(&bufferlock, flags);
 659        if (eerb->head != eerb->tail)
 660                mask = POLLIN | POLLRDNORM ;
 661        else
 662                mask = 0;
 663        spin_unlock_irqrestore(&bufferlock, flags);
 664        return mask;
 665}
 666
 667static const struct file_operations dasd_eer_fops = {
 668        .open           = &dasd_eer_open,
 669        .release        = &dasd_eer_close,
 670        .read           = &dasd_eer_read,
 671        .poll           = &dasd_eer_poll,
 672        .owner          = THIS_MODULE,
 673        .llseek         = noop_llseek,
 674};
 675
 676static struct miscdevice *dasd_eer_dev = NULL;
 677
 678int __init dasd_eer_init(void)
 679{
 680        int rc;
 681
 682        dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
 683        if (!dasd_eer_dev)
 684                return -ENOMEM;
 685
 686        dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
 687        dasd_eer_dev->name  = "dasd_eer";
 688        dasd_eer_dev->fops  = &dasd_eer_fops;
 689
 690        rc = misc_register(dasd_eer_dev);
 691        if (rc) {
 692                kfree(dasd_eer_dev);
 693                dasd_eer_dev = NULL;
 694                DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
 695                       "register misc device");
 696                return rc;
 697        }
 698
 699        return 0;
 700}
 701
 702void dasd_eer_exit(void)
 703{
 704        if (dasd_eer_dev) {
 705                misc_deregister(dasd_eer_dev);
 706                kfree(dasd_eer_dev);
 707                dasd_eer_dev = NULL;
 708        }
 709}
 710