1 /* The industrial I/O simple minimally locked ring buffer.
3 * Copyright (c) 2008 Jonathan Cameron
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 as published by
7 * the Free Software Foundation.
10 #include <linux/slab.h>
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/device.h>
14 #include <linux/workqueue.h>
18 static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
19 int bytes_per_datum, int length)
21 if ((length == 0) || (bytes_per_datum == 0))
23 __iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
24 ring->data = kmalloc(length*ring->buf.bpd, GFP_ATOMIC);
27 ring->last_written_p = NULL;
29 return ring->data ? 0 : -ENOMEM;
32 static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
34 spin_lock_init(&ring->use_lock);
37 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
42 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
44 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
45 spin_lock(&ring->use_lock);
47 spin_unlock(&ring->use_lock);
49 EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
51 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
53 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
54 spin_lock(&ring->use_lock);
56 spin_unlock(&ring->use_lock);
58 EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
61 /* Ring buffer related functionality */
62 /* Store to ring is typically called in the bh of a data ready interrupt handler
63 * in the device driver */
64 /* Lock always held if their is a chance this may be called */
65 /* Only one of these per ring may run concurrently - enforced by drivers */
66 static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
67 unsigned char *data, s64 timestamp)
71 unsigned char *temp_ptr, *change_test_ptr;
74 if (unlikely(ring->write_p == NULL)) {
75 ring->write_p = ring->data;
76 /* Doesn't actually matter if this is out of the set
77 * as long as the read pointer is valid before this
78 * passes it - guaranteed as set later in this function.
80 ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
82 /* Copy data to where ever the current write pointer says */
83 memcpy(ring->write_p, data, ring->buf.bpd);
85 /* Update the pointer used to get most recent value.
86 * Always valid as either points to latest or second latest value.
87 * Before this runs it is null and read attempts fail with -EAGAIN.
89 ring->last_written_p = ring->write_p;
91 /* temp_ptr used to ensure we never have an invalid pointer
92 * it may be slightly lagging, but never invalid
94 temp_ptr = ring->write_p + ring->buf.bpd;
95 /* End of ring, back to the beginning */
96 if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
97 temp_ptr = ring->data;
98 /* Update the write pointer
99 * always valid as long as this is the only function able to write.
100 * Care needed with smp systems to ensure more than one ring fill
101 * is never scheduled.
103 ring->write_p = temp_ptr;
105 if (ring->read_p == NULL)
106 ring->read_p = ring->data;
107 /* Buffer full - move the read pointer and create / escalate
109 /* Tricky case - if the read pointer moves before we adjust it.
110 * Handle by not pushing if it has moved - may result in occasional
111 * unnecessary buffer full events when it wasn't quite true.
113 else if (ring->write_p == ring->read_p) {
114 change_test_ptr = ring->read_p;
115 temp_ptr = change_test_ptr + ring->buf.bpd;
117 == ring->data + ring->buf.length*ring->buf.bpd) {
118 temp_ptr = ring->data;
120 /* We are moving pointer on one because the ring is full. Any
121 * change to the read pointer will be this or greater.
123 if (change_test_ptr == ring->read_p)
124 ring->read_p = temp_ptr;
126 spin_lock(&ring->buf.shared_ev_pointer.lock);
128 ret = iio_push_or_escallate_ring_event(&ring->buf,
129 IIO_EVENT_CODE_RING_100_FULL, timestamp);
130 spin_unlock(&ring->buf.shared_ev_pointer.lock);
134 /* investigate if our event barrier has been passed */
135 /* There are definite 'issues' with this and chances of
136 * simultaneous read */
137 /* Also need to use loop count to ensure this only happens once */
138 ring->half_p += ring->buf.bpd;
139 if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
140 ring->half_p = ring->data;
141 if (ring->half_p == ring->read_p) {
142 spin_lock(&ring->buf.shared_ev_pointer.lock);
143 code = IIO_EVENT_CODE_RING_50_FULL;
144 ret = __iio_push_event(&ring->buf.ev_int,
147 &ring->buf.shared_ev_pointer);
148 spin_unlock(&ring->buf.shared_ev_pointer.lock);
154 int iio_rip_sw_rb(struct iio_ring_buffer *r,
155 size_t count, u8 **data, int *dead_offset)
157 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
159 u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
163 /* A userspace program has probably made an error if it tries to
164 * read something that is not a whole number of bpds.
167 if (count % ring->buf.bpd) {
169 printk(KERN_INFO "Ring buffer read request not whole number of"
170 "samples: Request bytes %zd, Current bpd %d\n",
171 count, ring->buf.bpd);
174 /* Limit size to whole of ring buffer */
175 bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);
177 *data = kmalloc(bytes_to_rip, GFP_KERNEL);
183 /* build local copy */
184 initial_read_p = ring->read_p;
185 if (unlikely(initial_read_p == NULL)) { /* No data here as yet */
187 goto error_free_data_cpy;
190 initial_write_p = ring->write_p;
192 /* Need a consistent pair */
193 while ((initial_read_p != ring->read_p)
194 || (initial_write_p != ring->write_p)) {
195 initial_read_p = ring->read_p;
196 initial_write_p = ring->write_p;
198 if (initial_write_p == initial_read_p) {
199 /* No new data available.*/
201 goto error_free_data_cpy;
204 if (initial_write_p >= initial_read_p + bytes_to_rip) {
205 /* write_p is greater than necessary, all is easy */
206 max_copied = bytes_to_rip;
207 memcpy(*data, initial_read_p, max_copied);
208 end_read_p = initial_read_p + max_copied;
209 } else if (initial_write_p > initial_read_p) {
210 /*not enough data to cpy */
211 max_copied = initial_write_p - initial_read_p;
212 memcpy(*data, initial_read_p, max_copied);
213 end_read_p = initial_write_p;
215 /* going through 'end' of ring buffer */
216 max_copied = ring->data
217 + ring->buf.length*ring->buf.bpd - initial_read_p;
218 memcpy(*data, initial_read_p, max_copied);
219 /* possible we are done if we align precisely with end */
220 if (max_copied == bytes_to_rip)
221 end_read_p = ring->data;
222 else if (initial_write_p
223 > ring->data + bytes_to_rip - max_copied) {
224 /* enough data to finish */
225 memcpy(*data + max_copied, ring->data,
226 bytes_to_rip - max_copied);
227 max_copied = bytes_to_rip;
228 end_read_p = ring->data + (bytes_to_rip - max_copied);
229 } else { /* not enough data */
230 memcpy(*data + max_copied, ring->data,
231 initial_write_p - ring->data);
232 max_copied += initial_write_p - ring->data;
233 end_read_p = initial_write_p;
236 /* Now to verify which section was cleanly copied - i.e. how far
237 * read pointer has been pushed */
238 current_read_p = ring->read_p;
240 if (initial_read_p <= current_read_p)
241 *dead_offset = current_read_p - initial_read_p;
243 *dead_offset = ring->buf.length*ring->buf.bpd
244 - (initial_read_p - current_read_p);
246 /* possible issue if the initial write has been lapped or indeed
247 * the point we were reading to has been passed */
248 /* No valid data read.
249 * In this case the read pointer is already correct having been
250 * pushed further than we would look. */
251 if (max_copied - *dead_offset < 0) {
253 goto error_free_data_cpy;
256 /* setup the next read position */
257 /* Beware, this may fail due to concurrency fun and games.
258 * Possible that sufficient fill commands have run to push the read
259 * pointer past where we would be after the rip. If this occurs, leave
262 /* Tricky - deal with loops */
264 while (ring->read_p != end_read_p)
265 ring->read_p = end_read_p;
267 return max_copied - *dead_offset;
274 EXPORT_SYMBOL(iio_rip_sw_rb);
276 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
278 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
279 return iio_store_to_sw_ring(ring, data, timestamp);
281 EXPORT_SYMBOL(iio_store_to_sw_rb);
283 static int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
286 unsigned char *last_written_p_copy;
288 iio_mark_sw_rb_in_use(&ring->buf);
291 last_written_p_copy = ring->last_written_p;
292 barrier(); /*unnessecary? */
293 /* Check there is anything here */
294 if (last_written_p_copy == NULL)
296 memcpy(data, last_written_p_copy, ring->buf.bpd);
298 if (unlikely(ring->last_written_p != last_written_p_copy))
301 iio_unmark_sw_rb_in_use(&ring->buf);
305 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
308 return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
310 EXPORT_SYMBOL(iio_read_last_from_sw_rb);
312 int iio_request_update_sw_rb(struct iio_ring_buffer *r)
315 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
317 spin_lock(&ring->use_lock);
318 if (!ring->update_needed)
320 if (ring->use_count) {
324 __iio_free_sw_ring_buffer(ring);
325 ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bpd,
328 spin_unlock(&ring->use_lock);
331 EXPORT_SYMBOL(iio_request_update_sw_rb);
333 int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
335 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
336 return ring->buf.bpd;
338 EXPORT_SYMBOL(iio_get_bpd_sw_rb);
340 int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
344 if (r->access.mark_param_change)
345 r->access.mark_param_change(r);
349 EXPORT_SYMBOL(iio_set_bpd_sw_rb);
351 int iio_get_length_sw_rb(struct iio_ring_buffer *r)
355 EXPORT_SYMBOL(iio_get_length_sw_rb);
357 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
359 if (r->length != length) {
361 if (r->access.mark_param_change)
362 r->access.mark_param_change(r);
366 EXPORT_SYMBOL(iio_set_length_sw_rb);
368 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
370 struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
371 ring->update_needed = true;
374 EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
376 static void iio_sw_rb_release(struct device *dev)
378 struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
379 kfree(iio_to_sw_ring(r));
382 static IIO_RING_ENABLE_ATTR;
383 static IIO_RING_BPS_ATTR;
384 static IIO_RING_LENGTH_ATTR;
386 /* Standard set of ring buffer attributes */
387 static struct attribute *iio_ring_attributes[] = {
388 &dev_attr_length.attr,
390 &dev_attr_ring_enable.attr,
394 static struct attribute_group iio_ring_attribute_group = {
395 .attrs = iio_ring_attributes,
398 static const struct attribute_group *iio_ring_attribute_groups[] = {
399 &iio_ring_attribute_group,
403 static struct device_type iio_sw_ring_type = {
404 .release = iio_sw_rb_release,
405 .groups = iio_ring_attribute_groups,
408 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
410 struct iio_ring_buffer *buf;
411 struct iio_sw_ring_buffer *ring;
413 ring = kzalloc(sizeof *ring, GFP_KERNEL);
417 iio_ring_buffer_init(buf, indio_dev);
418 __iio_init_sw_ring_buffer(ring);
419 buf->dev.type = &iio_sw_ring_type;
420 device_initialize(&buf->dev);
421 buf->dev.parent = &indio_dev->dev;
422 buf->dev.bus = &iio_bus_type;
423 dev_set_drvdata(&buf->dev, (void *)buf);
427 EXPORT_SYMBOL(iio_sw_rb_allocate);
429 void iio_sw_rb_free(struct iio_ring_buffer *r)
432 iio_put_ring_buffer(r);
434 EXPORT_SYMBOL(iio_sw_rb_free);
436 int iio_sw_ring_preenable(struct iio_dev *indio_dev)
439 dev_dbg(&indio_dev->dev, "%s\n", __func__);
440 /* Check if there are any scan elements enabled, if not fail*/
441 if (!(indio_dev->scan_count || indio_dev->scan_timestamp))
443 if (indio_dev->scan_timestamp)
444 if (indio_dev->scan_count)
445 /* Timestamp (aligned to s64) and data */
446 size = (((indio_dev->scan_count * indio_dev->ring->bpe)
448 & ~(sizeof(s64) - 1))
450 else /* Timestamp only */
453 size = indio_dev->scan_count * indio_dev->ring->bpe;
454 indio_dev->ring->access.set_bpd(indio_dev->ring, size);
458 EXPORT_SYMBOL(iio_sw_ring_preenable);
460 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s)
462 struct iio_sw_ring_helper_state *st
463 = container_of(work_s, struct iio_sw_ring_helper_state,
464 work_trigger_to_ring);
466 size_t datasize = st->indio_dev
467 ->ring->access.get_bpd(st->indio_dev->ring);
468 char *data = kmalloc(datasize, GFP_KERNEL);
471 dev_err(st->indio_dev->dev.parent,
472 "memory alloc failed in ring bh");
476 if (st->indio_dev->scan_count)
477 len = st->get_ring_element(st, data);
479 /* Guaranteed to be aligned with 8 byte boundary */
480 if (st->indio_dev->scan_timestamp)
481 *(s64 *)(((u32)data + len
482 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
483 = st->last_timestamp;
484 st->indio_dev->ring->access.store_to(st->indio_dev->ring,
488 iio_trigger_notify_done(st->indio_dev->trig);
493 EXPORT_SYMBOL(iio_sw_trigger_bh_to_ring);
495 void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time)
496 { struct iio_sw_ring_helper_state *h
497 = iio_dev_get_devdata(indio_dev);
498 h->last_timestamp = time;
499 schedule_work(&h->work_trigger_to_ring);
501 EXPORT_SYMBOL(iio_sw_poll_func_th);
503 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
504 MODULE_LICENSE("GPL");