dasd_eer.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  Character device driver for extended error reporting.
  4 *
  5 *  Copyright IBM Corp. 2005
  6 *  extended error reporting for DASD ECKD devices
  7 *  Author(s): Stefan Weinhuber <wein@de.ibm.com>
  8 */
  9
 10#include <linux/export.h>
 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 <linux/uaccess.h>
 24#include <linux/atomic.h>
 25#include <asm/ebcdic.h>
 26
 27#include "dasd_int.h"
 28#include "dasd_eckd.h"
 29
 30/*
 31 * SECTION: the internal buffer
 32 */
 33
 34/*
 35 * The internal buffer is meant to store obaque blobs of data, so it does
 36 * not know of higher level concepts like triggers.
 37 * It consists of a number of pages that are used as a ringbuffer. Each data
 38 * blob is stored in a simple record that consists of an integer, which
 39 * contains the size of the following data, and the data bytes themselfes.
 40 *
 41 * To allow for multiple independent readers we create one internal buffer
 42 * each time the device is opened and destroy the buffer when the file is
 43 * closed again. The number of pages used for this buffer is determined by
 44 * the module parmeter eer_pages.
 45 *
 46 * One record can be written to a buffer by using the functions
 47 * - dasd_eer_start_record (one time per record to write the size to the
 48 *                          buffer and reserve the space for the data)
 49 * - dasd_eer_write_buffer (one or more times per record to write the data)
 50 * The data can be written in several steps but you will have to compute
 51 * the total size up front for the invocation of dasd_eer_start_record.
 52 * If the ringbuffer is full, dasd_eer_start_record will remove the required
 53 * number of old records.
 54 *
 55 * A record is typically read in two steps, first read the integer that
 56 * specifies the size of the following data, then read the data.
 57 * Both can be done by
 58 * - dasd_eer_read_buffer
 59 *
 60 * For all mentioned functions you need to get the bufferlock first and keep
 61 * it until a complete record is written or read.
 62 *
 63 * All information necessary to keep track of an internal buffer is kept in
 64 * a struct eerbuffer. The buffer specific to a file pointer is strored in
 65 * the private_data field of that file. To be able to write data to all
 66 * existing buffers, each buffer is also added to the bufferlist.
 67 * If the user does not want to read a complete record in one go, we have to
 68 * keep track of the rest of the record. residual stores the number of bytes
 69 * that are still to deliver. If the rest of the record is invalidated between
 70 * two reads then residual will be set to -1 so that the next read will fail.
 71 * All entries in the eerbuffer structure are protected with the bufferlock.
 72 * To avoid races between writing to a buffer on the one side and creating
 73 * and destroying buffers on the other side, the bufferlock must also be used
 74 * to protect the bufferlist.
 75 */
 76
 77static int eer_pages = 5;
 78module_param(eer_pages, int, S_IRUGO|S_IWUSR);
 79
 80struct eerbuffer {
 81	struct list_head list;
 82	char **buffer;
 83	int buffersize;
 84	int buffer_page_count;
 85	int head;
 86        int tail;
 87	int residual;
 88};
 89
 90static LIST_HEAD(bufferlist);
 91static DEFINE_SPINLOCK(bufferlock);
 92static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
 93
 94/*
 95 * How many free bytes are available on the buffer.
 96 * Needs to be called with bufferlock held.
 97 */
 98static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
 99{
100	if (eerb->head < eerb->tail)
101		return eerb->tail - eerb->head - 1;
102	return eerb->buffersize - eerb->head + eerb->tail -1;
103}
104
105/*
106 * How many bytes of buffer space are used.
107 * Needs to be called with bufferlock held.
108 */
109static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
110{
111
112	if (eerb->head >= eerb->tail)
113		return eerb->head - eerb->tail;
114	return eerb->buffersize - eerb->tail + eerb->head;
115}
116
117/*
118 * The dasd_eer_write_buffer function just copies count bytes of data
119 * to the buffer. Make sure to call dasd_eer_start_record first, to
120 * make sure that enough free space is available.
121 * Needs to be called with bufferlock held.
122 */
123static void dasd_eer_write_buffer(struct eerbuffer *eerb,
124				  char *data, int count)
125{
126
127	unsigned long headindex,localhead;
128	unsigned long rest, len;
129	char *nextdata;
130
131	nextdata = data;
132	rest = count;
133	while (rest > 0) {
134 		headindex = eerb->head / PAGE_SIZE;
135 		localhead = eerb->head % PAGE_SIZE;
136		len = min(rest, PAGE_SIZE - localhead);
137		memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
138		nextdata += len;
139		rest -= len;
140		eerb->head += len;
141		if (eerb->head == eerb->buffersize)
142			eerb->head = 0; /* wrap around */
143		BUG_ON(eerb->head > eerb->buffersize);
144	}
145}
146
147/*
148 * Needs to be called with bufferlock held.
149 */
150static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
151{
152
153	unsigned long tailindex,localtail;
154	unsigned long rest, len, finalcount;
155	char *nextdata;
156
157	finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
158	nextdata = data;
159	rest = finalcount;
160	while (rest > 0) {
161 		tailindex = eerb->tail / PAGE_SIZE;
162 		localtail = eerb->tail % PAGE_SIZE;
163		len = min(rest, PAGE_SIZE - localtail);
164		memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
165		nextdata += len;
166		rest -= len;
167		eerb->tail += len;
168		if (eerb->tail == eerb->buffersize)
169			eerb->tail = 0; /* wrap around */
170		BUG_ON(eerb->tail > eerb->buffersize);
171	}
172	return finalcount;
173}
174
175/*
176 * Whenever you want to write a blob of data to the internal buffer you
177 * have to start by using this function first. It will write the number
178 * of bytes that will be written to the buffer. If necessary it will remove
179 * old records to make room for the new one.
180 * Needs to be called with bufferlock held.
181 */
182static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
183{
184	int tailcount;
185
186	if (count + sizeof(count) > eerb->buffersize)
187		return -ENOMEM;
188	while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
189		if (eerb->residual > 0) {
190			eerb->tail += eerb->residual;
191			if (eerb->tail >= eerb->buffersize)
192				eerb->tail -= eerb->buffersize;
193			eerb->residual = -1;
194		}
195		dasd_eer_read_buffer(eerb, (char *) &tailcount,
196				     sizeof(tailcount));
197		eerb->tail += tailcount;
198		if (eerb->tail >= eerb->buffersize)
199			eerb->tail -= eerb->buffersize;
200	}
201	dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
202
203	return 0;
204};
205
206/*
207 * Release pages that are not used anymore.
208 */
209static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
210{
211	int i;
212
213	for (i = 0; i < no_pages; i++)
214		free_page((unsigned long) buf[i]);
215}
216
217/*
218 * Allocate a new set of memory pages.
219 */
220static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
221{
222	int i;
223
224	for (i = 0; i < no_pages; i++) {
225		buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
226		if (!buf[i]) {
227			dasd_eer_free_buffer_pages(buf, i);
228			return -ENOMEM;
229		}
230	}
231	return 0;
232}
233
234/*
235 * SECTION: The extended error reporting functionality
236 */
237
238/*
239 * When a DASD device driver wants to report an error, it calls the
240 * function dasd_eer_write and gives the respective trigger ID as
241 * parameter. Currently there are four kinds of triggers:
242 *
243 * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
244 * DASD_EER_PPRCSUSPEND: PPRC was suspended
245 * DASD_EER_NOPATH:      There is no path to the device left.
246 * DASD_EER_STATECHANGE: The state of the device has changed.
247 *
248 * For the first three triggers all required information can be supplied by
249 * the caller. For these triggers a record is written by the function
250 * dasd_eer_write_standard_trigger.
251 *
252 * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
253 * status ccw need to be executed to gather the necessary sense data first.
254 * The dasd_eer_snss function will queue the SNSS request and the request
255 * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
256 * trigger.
257 *
258 * To avoid memory allocations at runtime, the necessary memory is allocated
259 * when the extended error reporting is enabled for a device (by
260 * dasd_eer_probe). There is one sense subsystem status request for each
261 * eer enabled DASD device. The presence of the cqr in device->eer_cqr
262 * indicates that eer is enable for the device. The use of the snss request
263 * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
264 * that the cqr is currently in use, dasd_eer_snss cannot start a second
265 * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
266 * the SNSS request will check the bit and call dasd_eer_snss again.
267 */
268
269#define SNSS_DATA_SIZE 44
270
271#define DASD_EER_BUSID_SIZE 10
272struct dasd_eer_header {
273	__u32 total_size;
274	__u32 trigger;
275	__u64 tv_sec;
276	__u64 tv_usec;
277	char busid[DASD_EER_BUSID_SIZE];
278} __attribute__ ((packed));
279
280/*
281 * The following function can be used for those triggers that have
282 * all necessary data available when the function is called.
283 * If the parameter cqr is not NULL, the chain of requests will be searched
284 * for valid sense data, and all valid sense data sets will be added to
285 * the triggers data.
286 */
287static void dasd_eer_write_standard_trigger(struct dasd_device *device,
288					    struct dasd_ccw_req *cqr,
289					    int trigger)
290{
291	struct dasd_ccw_req *temp_cqr;
292	int data_size;
293	struct timespec64 ts;
294	struct dasd_eer_header header;
295	unsigned long flags;
296	struct eerbuffer *eerb;
297	char *sense;
298
299	/* go through cqr chain and count the valid sense data sets */
300	data_size = 0;
301	for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
302		if (dasd_get_sense(&temp_cqr->irb))
303			data_size += 32;
304
305	header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
306	header.trigger = trigger;
307	ktime_get_real_ts64(&ts);
308	header.tv_sec = ts.tv_sec;
309	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
310	strscpy(header.busid, dev_name(&device->cdev->dev),
311		DASD_EER_BUSID_SIZE);
312
313	spin_lock_irqsave(&bufferlock, flags);
314	list_for_each_entry(eerb, &bufferlist, list) {
315		dasd_eer_start_record(eerb, header.total_size);
316		dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
317		for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers) {
318			sense = dasd_get_sense(&temp_cqr->irb);
319			if (sense)
320				dasd_eer_write_buffer(eerb, sense, 32);
321		}
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 */
331static 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 timespec64 ts;
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	ktime_get_real_ts64(&ts);
351	header.tv_sec = ts.tv_sec;
352	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
353	strscpy(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 */
372void 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	case DASD_EER_NOSPC:
384	case DASD_EER_AUTOQUIESCE:
385		dasd_eer_write_standard_trigger(device, NULL, id);
386		break;
387	case DASD_EER_STATECHANGE:
388		dasd_eer_write_snss_trigger(device, cqr, id);
389		break;
390	default: /* unknown trigger, so we write it without any sense data */
391		dasd_eer_write_standard_trigger(device, NULL, id);
392		break;
393	}
394}
395EXPORT_SYMBOL(dasd_eer_write);
396
397/*
398 * Start a sense subsystem status request.
399 * Needs to be called with the device held.
400 */
401void dasd_eer_snss(struct dasd_device *device)
402{
403	struct dasd_ccw_req *cqr;
404
405	cqr = device->eer_cqr;
406	if (!cqr)	/* Device not eer enabled. */
407		return;
408	if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
409		/* Sense subsystem status request in use. */
410		set_bit(DASD_FLAG_EER_SNSS, &device->flags);
411		return;
412	}
413	/* cdev is already locked, can't use dasd_add_request_head */
414	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
415	cqr->status = DASD_CQR_QUEUED;
416	list_add(&cqr->devlist, &device->ccw_queue);
417	dasd_schedule_device_bh(device);
418}
419
420/*
421 * Callback function for use with sense subsystem status request.
422 */
423static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
424{
425	struct dasd_device *device = cqr->startdev;
426	unsigned long flags;
427
428	dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
429	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
430	if (device->eer_cqr == cqr) {
431		clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
432		if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
433			/* Another SNSS has been requested in the meantime. */
434			dasd_eer_snss(device);
435		cqr = NULL;
436	}
437	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
438	if (cqr)
439		/*
440		 * Extended error recovery has been switched off while
441		 * the SNSS request was running. It could even have
442		 * been switched off and on again in which case there
443		 * is a new ccw in device->eer_cqr. Free the "old"
444		 * snss request now.
445		 */
446		dasd_sfree_request(cqr, device);
447}
448
449/*
450 * Enable error reporting on a given device.
451 */
452int dasd_eer_enable(struct dasd_device *device)
453{
454	struct dasd_ccw_req *cqr = NULL;
455	unsigned long flags;
456	struct ccw1 *ccw;
457	int rc = 0;
458
459	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
460	if (device->eer_cqr)
461		goto out;
462	else if (!device->discipline ||
463		 strcmp(device->discipline->name, "ECKD"))
464		rc = -EMEDIUMTYPE;
465	else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
466		rc = -EBUSY;
467
468	if (rc)
469		goto out;
470
471	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
472				   SNSS_DATA_SIZE, device, NULL);
473	if (IS_ERR(cqr)) {
474		rc = -ENOMEM;
475		cqr = NULL;
476		goto out;
477	}
478
479	cqr->startdev = device;
480	cqr->retries = 255;
481	cqr->expires = 10 * HZ;
482	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
483	set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
484
485	ccw = cqr->cpaddr;
486	ccw->cmd_code = DASD_ECKD_CCW_SNSS;
487	ccw->count = SNSS_DATA_SIZE;
488	ccw->flags = 0;
489	ccw->cda = virt_to_dma32(cqr->data);
490
491	cqr->buildclk = get_tod_clock();
492	cqr->status = DASD_CQR_FILLED;
493	cqr->callback = dasd_eer_snss_cb;
494
495	if (!device->eer_cqr) {
496		device->eer_cqr = cqr;
497		cqr = NULL;
498	}
499
500out:
501	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
502
503	if (cqr)
504		dasd_sfree_request(cqr, device);
505
506	return rc;
507}
508
509/*
510 * Disable error reporting on a given device.
511 */
512void dasd_eer_disable(struct dasd_device *device)
513{
514	struct dasd_ccw_req *cqr;
515	unsigned long flags;
516	int in_use;
517
518	if (!device->eer_cqr)
519		return;
520	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
521	cqr = device->eer_cqr;
522	device->eer_cqr = NULL;
523	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
524	in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
525	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
526	if (cqr && !in_use)
527		dasd_sfree_request(cqr, device);
528}
529
530/*
531 * SECTION: the device operations
532 */
533
534/*
535 * On the one side we need a lock to access our internal buffer, on the
536 * other side a copy_to_user can sleep. So we need to copy the data we have
537 * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
538 */
539static char readbuffer[PAGE_SIZE];
540static DEFINE_MUTEX(readbuffer_mutex);
541
542static int dasd_eer_open(struct inode *inp, struct file *filp)
543{
544	struct eerbuffer *eerb;
545	unsigned long flags;
546
547	eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
548	if (!eerb)
549		return -ENOMEM;
550	eerb->buffer_page_count = eer_pages;
551	if (eerb->buffer_page_count < 1 ||
552	    eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
553		kfree(eerb);
554		DBF_EVENT(DBF_WARNING, "can't open device since module "
555			"parameter eer_pages is smaller than 1 or"
556			" bigger than %d", (int)(INT_MAX / PAGE_SIZE));
557		return -EINVAL;
558	}
559	eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
560	eerb->buffer = kmalloc_array(eerb->buffer_page_count, sizeof(char *),
561				     GFP_KERNEL);
562        if (!eerb->buffer) {
563		kfree(eerb);
564                return -ENOMEM;
565	}
566	if (dasd_eer_allocate_buffer_pages(eerb->buffer,
567					   eerb->buffer_page_count)) {
568		kfree(eerb->buffer);
569		kfree(eerb);
570		return -ENOMEM;
571	}
572	filp->private_data = eerb;
573	spin_lock_irqsave(&bufferlock, flags);
574	list_add(&eerb->list, &bufferlist);
575	spin_unlock_irqrestore(&bufferlock, flags);
576
577	return nonseekable_open(inp,filp);
578}
579
580static int dasd_eer_close(struct inode *inp, struct file *filp)
581{
582	struct eerbuffer *eerb;
583	unsigned long flags;
584
585	eerb = (struct eerbuffer *) filp->private_data;
586	spin_lock_irqsave(&bufferlock, flags);
587	list_del(&eerb->list);
588	spin_unlock_irqrestore(&bufferlock, flags);
589	dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
590	kfree(eerb->buffer);
591	kfree(eerb);
592
593	return 0;
594}
595
596static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
597			     size_t count, loff_t *ppos)
598{
599	int tc,rc;
600	int tailcount,effective_count;
601        unsigned long flags;
602	struct eerbuffer *eerb;
603
604	eerb = (struct eerbuffer *) filp->private_data;
605	if (mutex_lock_interruptible(&readbuffer_mutex))
606		return -ERESTARTSYS;
607
608	spin_lock_irqsave(&bufferlock, flags);
609
610	if (eerb->residual < 0) { /* the remainder of this record */
611		                  /* has been deleted             */
612		eerb->residual = 0;
613		spin_unlock_irqrestore(&bufferlock, flags);
614		mutex_unlock(&readbuffer_mutex);
615		return -EIO;
616	} else if (eerb->residual > 0) {
617		/* OK we still have a second half of a record to deliver */
618		effective_count = min(eerb->residual, (int) count);
619		eerb->residual -= effective_count;
620	} else {
621		tc = 0;
622		while (!tc) {
623			tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
624						  sizeof(tailcount));
625			if (!tc) {
626				/* no data available */
627				spin_unlock_irqrestore(&bufferlock, flags);
628				mutex_unlock(&readbuffer_mutex);
629				if (filp->f_flags & O_NONBLOCK)
630					return -EAGAIN;
631				rc = wait_event_interruptible(
632					dasd_eer_read_wait_queue,
633					eerb->head != eerb->tail);
634				if (rc)
635					return rc;
636				if (mutex_lock_interruptible(&readbuffer_mutex))
637					return -ERESTARTSYS;
638				spin_lock_irqsave(&bufferlock, flags);
639			}
640		}
641		WARN_ON(tc != sizeof(tailcount));
642		effective_count = min(tailcount,(int)count);
643		eerb->residual = tailcount - effective_count;
644	}
645
646	tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
647	WARN_ON(tc != effective_count);
648
649	spin_unlock_irqrestore(&bufferlock, flags);
650
651	if (copy_to_user(buf, readbuffer, effective_count)) {
652		mutex_unlock(&readbuffer_mutex);
653		return -EFAULT;
654	}
655
656	mutex_unlock(&readbuffer_mutex);
657	return effective_count;
658}
659
660static __poll_t dasd_eer_poll(struct file *filp, poll_table *ptable)
661{
662	__poll_t mask;
663	unsigned long flags;
664	struct eerbuffer *eerb;
665
666	eerb = (struct eerbuffer *) filp->private_data;
667	poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
668	spin_lock_irqsave(&bufferlock, flags);
669	if (eerb->head != eerb->tail)
670		mask = EPOLLIN | EPOLLRDNORM ;
671	else
672		mask = 0;
673	spin_unlock_irqrestore(&bufferlock, flags);
674	return mask;
675}
676
677static const struct file_operations dasd_eer_fops = {
678	.open		= &dasd_eer_open,
679	.release	= &dasd_eer_close,
680	.read		= &dasd_eer_read,
681	.poll		= &dasd_eer_poll,
682	.owner		= THIS_MODULE,
683	.llseek		= noop_llseek,
684};
685
686static struct miscdevice *dasd_eer_dev = NULL;
687
688int __init dasd_eer_init(void)
689{
690	int rc;
691
692	dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
693	if (!dasd_eer_dev)
694		return -ENOMEM;
695
696	dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
697	dasd_eer_dev->name  = "dasd_eer";
698	dasd_eer_dev->fops  = &dasd_eer_fops;
699
700	rc = misc_register(dasd_eer_dev);
701	if (rc) {
702		kfree(dasd_eer_dev);
703		dasd_eer_dev = NULL;
704		DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
705		       "register misc device");
706		return rc;
707	}
708
709	return 0;
710}
711
712void dasd_eer_exit(void)
713{
714	if (dasd_eer_dev) {
715		misc_deregister(dasd_eer_dev);
716		kfree(dasd_eer_dev);
717		dasd_eer_dev = NULL;
718	}
719}