kernel/2.6.29.6-aldebaran-rt/drivers/s390/block/dasd_eer.c

   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 #include <linux/init.h>
  10 #include <linux/fs.h>
  11 #include <linux/kernel.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/device.h>
  16 #include <linux/poll.h>
  17 #include <linux/mutex.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/err.h>
  20
  21 #include <asm/uaccess.h>
  22 #include <asm/atomic.h>
  23 #include <asm/ebcdic.h>
  24
  25 #include "dasd_int.h"
  26 #include "dasd_eckd.h"
  27
  28 #ifdef PRINTK_HEADER
  29 #undef PRINTK_HEADER
  30 #endif                          /* PRINTK_HEADER */
  31 #define PRINTK_HEADER "dasd(eer):"
  32
  33 /*
  34  * SECTION: the internal buffer
  35  */
  36
  37 /*
  38  * The internal buffer is meant to store obaque blobs of data, so it does
  39  * not know of higher level concepts like triggers.
  40  * It consists of a number of pages that are used as a ringbuffer. Each data
  41  * blob is stored in a simple record that consists of an integer, which
  42  * contains the size of the following data, and the data bytes themselfes.
  43  *
  44  * To allow for multiple independent readers we create one internal buffer
  45  * each time the device is opened and destroy the buffer when the file is
  46  * closed again. The number of pages used for this buffer is determined by
  47  * the module parmeter eer_pages.
  48  *
  49  * One record can be written to a buffer by using the functions
  50  * - dasd_eer_start_record (one time per record to write the size to the
  51  *                          buffer and reserve the space for the data)
  52  * - dasd_eer_write_buffer (one or more times per record to write the data)
  53  * The data can be written in several steps but you will have to compute
  54  * the total size up front for the invocation of dasd_eer_start_record.
  55  * If the ringbuffer is full, dasd_eer_start_record will remove the required
  56  * number of old records.
  57  *
  58  * A record is typically read in two steps, first read the integer that
  59  * specifies the size of the following data, then read the data.
  60  * Both can be done by
  61  * - dasd_eer_read_buffer
  62  *
  63  * For all mentioned functions you need to get the bufferlock first and keep
  64  * it until a complete record is written or read.
  65  *
  66  * All information necessary to keep track of an internal buffer is kept in
  67  * a struct eerbuffer. The buffer specific to a file pointer is strored in
  68  * the private_data field of that file. To be able to write data to all
  69  * existing buffers, each buffer is also added to the bufferlist.
  70  * If the user does not want to read a complete record in one go, we have to
  71  * keep track of the rest of the record. residual stores the number of bytes
  72  * that are still to deliver. If the rest of the record is invalidated between
  73  * two reads then residual will be set to -1 so that the next read will fail.
  74  * All entries in the eerbuffer structure are protected with the bufferlock.
  75  * To avoid races between writing to a buffer on the one side and creating
  76  * and destroying buffers on the other side, the bufferlock must also be used
  77  * to protect the bufferlist.
  78  */
  79
  80 static int eer_pages = 5;
  81 module_param(eer_pages, int, S_IRUGO|S_IWUSR);
  82
  83 struct eerbuffer {
  84         struct list_head list;
  85         char **buffer;
  86         int buffersize;
  87         int buffer_page_count;
  88         int head;
  89         int tail;
  90         int residual;
  91 };
  92
  93 static LIST_HEAD(bufferlist);
  94 static DEFINE_SPINLOCK(bufferlock);
  95 static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
  96
  97 /*
  98  * How many free bytes are available on the buffer.
  99  * Needs to be called with bufferlock held.
 100  */
 101 static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
 102 {
 103         if (eerb->head < eerb->tail)
 104                 return eerb->tail - eerb->head - 1;
 105         return eerb->buffersize - eerb->head + eerb->tail -1;
 106 }
 107
 108 /*
 109  * How many bytes of buffer space are used.
 110  * Needs to be called with bufferlock held.
 111  */
 112 static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
 113 {
 114
 115         if (eerb->head >= eerb->tail)
 116                 return eerb->head - eerb->tail;
 117         return eerb->buffersize - eerb->tail + eerb->head;
 118 }
 119
 120 /*
 121  * The dasd_eer_write_buffer function just copies count bytes of data
 122  * to the buffer. Make sure to call dasd_eer_start_record first, to
 123  * make sure that enough free space is available.
 124  * Needs to be called with bufferlock held.
 125  */
 126 static void dasd_eer_write_buffer(struct eerbuffer *eerb,
 127                                   char *data, int count)
 128 {
 129
 130         unsigned long headindex,localhead;
 131         unsigned long rest, len;
 132         char *nextdata;
 133
 134         nextdata = data;
 135         rest = count;
 136         while (rest > 0) {
 137                 headindex = eerb->head / PAGE_SIZE;
 138                 localhead = eerb->head % PAGE_SIZE;
 139                 len = min(rest, PAGE_SIZE - localhead);
 140                 memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
 141                 nextdata += len;
 142                 rest -= len;
 143                 eerb->head += len;
 144                 if (eerb->head == eerb->buffersize)
 145                         eerb->head = 0; /* wrap around */
 146                 BUG_ON(eerb->head > eerb->buffersize);
 147         }
 148 }
 149
 150 /*
 151  * Needs to be called with bufferlock held.
 152  */
 153 static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
 154 {
 155
 156         unsigned long tailindex,localtail;
 157         unsigned long rest, len, finalcount;
 158         char *nextdata;
 159
 160         finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
 161         nextdata = data;
 162         rest = finalcount;
 163         while (rest > 0) {
 164                 tailindex = eerb->tail / PAGE_SIZE;
 165                 localtail = eerb->tail % PAGE_SIZE;
 166                 len = min(rest, PAGE_SIZE - localtail);
 167                 memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
 168                 nextdata += len;
 169                 rest -= len;
 170                 eerb->tail += len;
 171                 if (eerb->tail == eerb->buffersize)
 172                         eerb->tail = 0; /* wrap around */
 173                 BUG_ON(eerb->tail > eerb->buffersize);
 174         }
 175         return finalcount;
 176 }
 177
 178 /*
 179  * Whenever you want to write a blob of data to the internal buffer you
 180  * have to start by using this function first. It will write the number
 181  * of bytes that will be written to the buffer. If necessary it will remove
 182  * old records to make room for the new one.
 183  * Needs to be called with bufferlock held.
 184  */
 185 static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
 186 {
 187         int tailcount;
 188
 189         if (count + sizeof(count) > eerb->buffersize)
 190                 return -ENOMEM;
 191         while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
 192                 if (eerb->residual > 0) {
 193                         eerb->tail += eerb->residual;
 194                         if (eerb->tail >= eerb->buffersize)
 195                                 eerb->tail -= eerb->buffersize;
 196                         eerb->residual = -1;
 197                 }
 198                 dasd_eer_read_buffer(eerb, (char *) &tailcount,
 199                                      sizeof(tailcount));
 200                 eerb->tail += tailcount;
 201                 if (eerb->tail >= eerb->buffersize)
 202                         eerb->tail -= eerb->buffersize;
 203         }
 204         dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
 205
 206         return 0;
 207 };
 208
 209 /*
 210  * Release pages that are not used anymore.
 211  */
 212 static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
 213 {
 214         int i;
 215
 216         for (i = 0; i < no_pages; i++)
 217                 free_page((unsigned long) buf[i]);
 218 }
 219
 220 /*
 221  * Allocate a new set of memory pages.
 222  */
 223 static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
 224 {
 225         int i;
 226
 227         for (i = 0; i < no_pages; i++) {
 228                 buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
 229                 if (!buf[i]) {
 230                         dasd_eer_free_buffer_pages(buf, i);
 231                         return -ENOMEM;
 232                 }
 233         }
 234         return 0;
 235 }
 236
 237 /*
 238  * SECTION: The extended error reporting functionality
 239  */
 240
 241 /*
 242  * When a DASD device driver wants to report an error, it calls the
 243  * function dasd_eer_write and gives the respective trigger ID as
 244  * parameter. Currently there are four kinds of triggers:
 245  *
 246  * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
 247  * DASD_EER_PPRCSUSPEND: PPRC was suspended
 248  * DASD_EER_NOPATH:      There is no path to the device left.
 249  * DASD_EER_STATECHANGE: The state of the device has changed.
 250  *
 251  * For the first three triggers all required information can be supplied by
 252  * the caller. For these triggers a record is written by the function
 253  * dasd_eer_write_standard_trigger.
 254  *
 255  * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
 256  * status ccw need to be executed to gather the necessary sense data first.
 257  * The dasd_eer_snss function will queue the SNSS request and the request
 258  * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
 259  * trigger.
 260  *
 261  * To avoid memory allocations at runtime, the necessary memory is allocated
 262  * when the extended error reporting is enabled for a device (by
 263  * dasd_eer_probe). There is one sense subsystem status request for each
 264  * eer enabled DASD device. The presence of the cqr in device->eer_cqr
 265  * indicates that eer is enable for the device. The use of the snss request
 266  * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
 267  * that the cqr is currently in use, dasd_eer_snss cannot start a second
 268  * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
 269  * the SNSS request will check the bit and call dasd_eer_snss again.
 270  */
 271
 272 #define SNSS_DATA_SIZE 44
 273
 274 #define DASD_EER_BUSID_SIZE 10
 275 struct dasd_eer_header {
 276         __u32 total_size;
 277         __u32 trigger;
 278         __u64 tv_sec;
 279         __u64 tv_usec;
 280         char busid[DASD_EER_BUSID_SIZE];
 281 } __attribute__ ((packed));
 282
 283 /*
 284  * The following function can be used for those triggers that have
 285  * all necessary data available when the function is called.
 286  * If the parameter cqr is not NULL, the chain of requests will be searched
 287  * for valid sense data, and all valid sense data sets will be added to
 288  * the triggers data.
 289  */
 290 static void dasd_eer_write_standard_trigger(struct dasd_device *device,
 291                                             struct dasd_ccw_req *cqr,
 292                                             int trigger)
 293 {
 294         struct dasd_ccw_req *temp_cqr;
 295         int data_size;
 296         struct timeval tv;
 297         struct dasd_eer_header header;
 298         unsigned long flags;
 299         struct eerbuffer *eerb;
 300
 301         /* go through cqr chain and count the valid sense data sets */
 302         data_size = 0;
 303         for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
 304                 if (temp_cqr->irb.esw.esw0.erw.cons)
 305                         data_size += 32;
 306
 307         header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 308         header.trigger = trigger;
 309         do_gettimeofday(&tv);
 310         header.tv_sec = tv.tv_sec;
 311         header.tv_usec = tv.tv_usec;
 312         strncpy(header.busid, dev_name(&device->cdev->dev),
 313                 DASD_EER_BUSID_SIZE);
 314
 315         spin_lock_irqsave(&bufferlock, flags);
 316         list_for_each_entry(eerb, &bufferlist, list) {
 317                 dasd_eer_start_record(eerb, header.total_size);
 318                 dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
 319                 for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
 320                         if (temp_cqr->irb.esw.esw0.erw.cons)
 321                                 dasd_eer_write_buffer(eerb, cqr->irb.ecw, 32);
 322                 dasd_eer_write_buffer(eerb, "EOR", 4);
 323         }
 324         spin_unlock_irqrestore(&bufferlock, flags);
 325         wake_up_interruptible(&dasd_eer_read_wait_queue);
 326 }
 327
 328 /*
 329  * This function writes a DASD_EER_STATECHANGE trigger.
 330  */
 331 static void dasd_eer_write_snss_trigger(struct dasd_device *device,
 332                                         struct dasd_ccw_req *cqr,
 333                                         int trigger)
 334 {
 335         int data_size;
 336         int snss_rc;
 337         struct timeval tv;
 338         struct dasd_eer_header header;
 339         unsigned long flags;
 340         struct eerbuffer *eerb;
 341
 342         snss_rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
 343         if (snss_rc)
 344                 data_size = 0;
 345         else
 346                 data_size = SNSS_DATA_SIZE;
 347
 348         header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
 349         header.trigger = DASD_EER_STATECHANGE;
 350         do_gettimeofday(&tv);
 351         header.tv_sec = tv.tv_sec;
 352         header.tv_usec = tv.tv_usec;
 353         strncpy(header.busid, dev_name(&device->cdev->dev),
 354                 DASD_EER_BUSID_SIZE);
 355
 356         spin_lock_irqsave(&bufferlock, flags);
 357         list_for_each_entry(eerb, &bufferlist, list) {
 358                 dasd_eer_start_record(eerb, header.total_size);
 359                 dasd_eer_write_buffer(eerb, (char *) &header , sizeof(header));
 360                 if (!snss_rc)
 361                         dasd_eer_write_buffer(eerb, cqr->data, SNSS_DATA_SIZE);
 362                 dasd_eer_write_buffer(eerb, "EOR", 4);
 363         }
 364         spin_unlock_irqrestore(&bufferlock, flags);
 365         wake_up_interruptible(&dasd_eer_read_wait_queue);
 366 }
 367
 368 /*
 369  * This function is called for all triggers. It calls the appropriate
 370  * function that writes the actual trigger records.
 371  */
 372 void dasd_eer_write(struct dasd_device *device, struct dasd_ccw_req *cqr,
 373                     unsigned int id)
 374 {
 375         if (!device->eer_cqr)
 376                 return;
 377         switch (id) {
 378         case DASD_EER_FATALERROR:
 379         case DASD_EER_PPRCSUSPEND:
 380                 dasd_eer_write_standard_trigger(device, cqr, id);
 381                 break;
 382         case DASD_EER_NOPATH:
 383                 dasd_eer_write_standard_trigger(device, NULL, id);
 384                 break;
 385         case DASD_EER_STATECHANGE:
 386                 dasd_eer_write_snss_trigger(device, cqr, id);
 387                 break;
 388         default: /* unknown trigger, so we write it without any sense data */
 389                 dasd_eer_write_standard_trigger(device, NULL, id);
 390                 break;
 391         }
 392 }
 393 EXPORT_SYMBOL(dasd_eer_write);
 394
 395 /*
 396  * Start a sense subsystem status request.
 397  * Needs to be called with the device held.
 398  */
 399 void dasd_eer_snss(struct dasd_device *device)
 400 {
 401         struct dasd_ccw_req *cqr;
 402
 403         cqr = device->eer_cqr;
 404         if (!cqr)       /* Device not eer enabled. */
 405                 return;
 406         if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
 407                 /* Sense subsystem status request in use. */
 408                 set_bit(DASD_FLAG_EER_SNSS, &device->flags);
 409                 return;
 410         }
 411         /* cdev is already locked, can't use dasd_add_request_head */
 412         clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 413         cqr->status = DASD_CQR_QUEUED;
 414         list_add(&cqr->devlist, &device->ccw_queue);
 415         dasd_schedule_device_bh(device);
 416 }
 417
 418 /*
 419  * Callback function for use with sense subsystem status request.
 420  */
 421 static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
 422 {
 423         struct dasd_device *device = cqr->startdev;
 424         unsigned long flags;
 425
 426         dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
 427         spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 428         if (device->eer_cqr == cqr) {
 429                 clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 430                 if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
 431                         /* Another SNSS has been requested in the meantime. */
 432                         dasd_eer_snss(device);
 433                 cqr = NULL;
 434         }
 435         spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 436         if (cqr)
 437                 /*
 438                  * Extended error recovery has been switched off while
 439                  * the SNSS request was running. It could even have
 440                  * been switched off and on again in which case there
 441                  * is a new ccw in device->eer_cqr. Free the "old"
 442                  * snss request now.
 443                  */
 444                 dasd_kfree_request(cqr, device);
 445 }
 446
 447 /*
 448  * Enable error reporting on a given device.
 449  */
 450 int dasd_eer_enable(struct dasd_device *device)
 451 {
 452         struct dasd_ccw_req *cqr;
 453         unsigned long flags;
 454
 455         if (device->eer_cqr)
 456                 return 0;
 457
 458         if (!device->discipline || strcmp(device->discipline->name, "ECKD"))
 459                 return -EPERM;  /* FIXME: -EMEDIUMTYPE ? */
 460
 461         cqr = dasd_kmalloc_request("ECKD", 1 /* SNSS */,
 462                                    SNSS_DATA_SIZE, device);
 463         if (IS_ERR(cqr))
 464                 return -ENOMEM;
 465
 466         cqr->startdev = device;
 467         cqr->retries = 255;
 468         cqr->expires = 10 * HZ;
 469         clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
 470
 471         cqr->cpaddr->cmd_code = DASD_ECKD_CCW_SNSS;
 472         cqr->cpaddr->count = SNSS_DATA_SIZE;
 473         cqr->cpaddr->flags = 0;
 474         cqr->cpaddr->cda = (__u32)(addr_t) cqr->data;
 475
 476         cqr->buildclk = get_clock();
 477         cqr->status = DASD_CQR_FILLED;
 478         cqr->callback = dasd_eer_snss_cb;
 479
 480         spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 481         if (!device->eer_cqr) {
 482                 device->eer_cqr = cqr;
 483                 cqr = NULL;
 484         }
 485         spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 486         if (cqr)
 487                 dasd_kfree_request(cqr, device);
 488         return 0;
 489 }
 490
 491 /*
 492  * Disable error reporting on a given device.
 493  */
 494 void dasd_eer_disable(struct dasd_device *device)
 495 {
 496         struct dasd_ccw_req *cqr;
 497         unsigned long flags;
 498         int in_use;
 499
 500         if (!device->eer_cqr)
 501                 return;
 502         spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 503         cqr = device->eer_cqr;
 504         device->eer_cqr = NULL;
 505         clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
 506         in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
 507         spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
 508         if (cqr && !in_use)
 509                 dasd_kfree_request(cqr, device);
 510 }
 511
 512 /*
 513  * SECTION: the device operations
 514  */
 515
 516 /*
 517  * On the one side we need a lock to access our internal buffer, on the
 518  * other side a copy_to_user can sleep. So we need to copy the data we have
 519  * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
 520  */
 521 static char readbuffer[PAGE_SIZE];
 522 static DEFINE_MUTEX(readbuffer_mutex);
 523
 524 static int dasd_eer_open(struct inode *inp, struct file *filp)
 525 {
 526         struct eerbuffer *eerb;
 527         unsigned long flags;
 528
 529         eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
 530         if (!eerb)
 531                 return -ENOMEM;
 532         lock_kernel();
 533         eerb->buffer_page_count = eer_pages;
 534         if (eerb->buffer_page_count < 1 ||
 535             eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
 536                 kfree(eerb);
 537                 MESSAGE(KERN_WARNING, "can't open device since module "
 538                         "parameter eer_pages is smaller than 1 or"
 539                         " bigger than %d", (int)(INT_MAX / PAGE_SIZE));
 540                 unlock_kernel();
 541                 return -EINVAL;
 542         }
 543         eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
 544         eerb->buffer = kmalloc(eerb->buffer_page_count * sizeof(char *),
 545                                GFP_KERNEL);
 546         if (!eerb->buffer) {
 547                 kfree(eerb);
 548                 unlock_kernel();
 549                 return -ENOMEM;
 550         }
 551         if (dasd_eer_allocate_buffer_pages(eerb->buffer,
 552                                            eerb->buffer_page_count)) {
 553                 kfree(eerb->buffer);
 554                 kfree(eerb);
 555                 unlock_kernel();
 556                 return -ENOMEM;
 557         }
 558         filp->private_data = eerb;
 559         spin_lock_irqsave(&bufferlock, flags);
 560         list_add(&eerb->list, &bufferlist);
 561         spin_unlock_irqrestore(&bufferlock, flags);
 562
 563         unlock_kernel();
 564         return nonseekable_open(inp,filp);
 565 }
 566
 567 static int dasd_eer_close(struct inode *inp, struct file *filp)
 568 {
 569         struct eerbuffer *eerb;
 570         unsigned long flags;
 571
 572         eerb = (struct eerbuffer *) filp->private_data;
 573         spin_lock_irqsave(&bufferlock, flags);
 574         list_del(&eerb->list);
 575         spin_unlock_irqrestore(&bufferlock, flags);
 576         dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
 577         kfree(eerb->buffer);
 578         kfree(eerb);
 579
 580         return 0;
 581 }
 582
 583 static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
 584                              size_t count, loff_t *ppos)
 585 {
 586         int tc,rc;
 587         int tailcount,effective_count;
 588         unsigned long flags;
 589         struct eerbuffer *eerb;
 590
 591         eerb = (struct eerbuffer *) filp->private_data;
 592         if (mutex_lock_interruptible(&readbuffer_mutex))
 593                 return -ERESTARTSYS;
 594
 595         spin_lock_irqsave(&bufferlock, flags);
 596
 597         if (eerb->residual < 0) { /* the remainder of this record */
 598                                   /* has been deleted             */
 599                 eerb->residual = 0;
 600                 spin_unlock_irqrestore(&bufferlock, flags);
 601                 mutex_unlock(&readbuffer_mutex);
 602                 return -EIO;
 603         } else if (eerb->residual > 0) {
 604                 /* OK we still have a second half of a record to deliver */
 605                 effective_count = min(eerb->residual, (int) count);
 606                 eerb->residual -= effective_count;
 607         } else {
 608                 tc = 0;
 609                 while (!tc) {
 610                         tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
 611                                                   sizeof(tailcount));
 612                         if (!tc) {
 613                                 /* no data available */
 614                                 spin_unlock_irqrestore(&bufferlock, flags);
 615                                 mutex_unlock(&readbuffer_mutex);
 616                                 if (filp->f_flags & O_NONBLOCK)
 617                                         return -EAGAIN;
 618                                 rc = wait_event_interruptible(
 619                                         dasd_eer_read_wait_queue,
 620                                         eerb->head != eerb->tail);
 621                                 if (rc)
 622                                         return rc;
 623                                 if (mutex_lock_interruptible(&readbuffer_mutex))
 624                                         return -ERESTARTSYS;
 625                                 spin_lock_irqsave(&bufferlock, flags);
 626                         }
 627                 }
 628                 WARN_ON(tc != sizeof(tailcount));
 629                 effective_count = min(tailcount,(int)count);
 630                 eerb->residual = tailcount - effective_count;
 631         }
 632
 633         tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
 634         WARN_ON(tc != effective_count);
 635
 636         spin_unlock_irqrestore(&bufferlock, flags);
 637
 638         if (copy_to_user(buf, readbuffer, effective_count)) {
 639                 mutex_unlock(&readbuffer_mutex);
 640                 return -EFAULT;
 641         }
 642
 643         mutex_unlock(&readbuffer_mutex);
 644         return effective_count;
 645 }
 646
 647 static unsigned int dasd_eer_poll(struct file *filp, poll_table *ptable)
 648 {
 649         unsigned int mask;
 650         unsigned long flags;
 651         struct eerbuffer *eerb;
 652
 653         eerb = (struct eerbuffer *) filp->private_data;
 654         poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
 655         spin_lock_irqsave(&bufferlock, flags);
 656         if (eerb->head != eerb->tail)
 657                 mask = POLLIN | POLLRDNORM ;
 658         else
 659                 mask = 0;
 660         spin_unlock_irqrestore(&bufferlock, flags);
 661         return mask;
 662 }
 663
 664 static const struct file_operations dasd_eer_fops = {
 665         .open           = &dasd_eer_open,
 666         .release        = &dasd_eer_close,
 667         .read           = &dasd_eer_read,
 668         .poll           = &dasd_eer_poll,
 669         .owner          = THIS_MODULE,
 670 };
 671
 672 static struct miscdevice *dasd_eer_dev = NULL;
 673
 674 int __init dasd_eer_init(void)
 675 {
 676         int rc;
 677
 678         dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
 679         if (!dasd_eer_dev)
 680                 return -ENOMEM;
 681
 682         dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
 683         dasd_eer_dev->name  = "dasd_eer";
 684         dasd_eer_dev->fops  = &dasd_eer_fops;
 685
 686         rc = misc_register(dasd_eer_dev);
 687         if (rc) {
 688                 kfree(dasd_eer_dev);
 689                 dasd_eer_dev = NULL;
 690                 MESSAGE(KERN_ERR, "%s", "dasd_eer_init could not "
 691                        "register misc device");
 692                 return rc;
 693         }
 694
 695         return 0;
 696 }
 697
 698 void dasd_eer_exit(void)
 699 {
 700         if (dasd_eer_dev) {
 701                 WARN_ON(misc_deregister(dasd_eer_dev) != 0);
 702                 kfree(dasd_eer_dev);
 703                 dasd_eer_dev = NULL;
 704         }
 705 }