1 | // SPDX-License-Identifier: GPL-2.0+ |
2 | /* |
3 | * comedi_buf.c |
4 | * |
5 | * COMEDI - Linux Control and Measurement Device Interface |
6 | * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org> |
7 | * Copyright (C) 2002 Frank Mori Hess <fmhess@users.sourceforge.net> |
8 | */ |
9 | |
10 | #include <linux/vmalloc.h> |
11 | #include <linux/slab.h> |
12 | #include <linux/comedi/comedidev.h> |
13 | #include "comedi_internal.h" |
14 | |
15 | #ifdef PAGE_KERNEL_NOCACHE |
16 | #define COMEDI_PAGE_PROTECTION PAGE_KERNEL_NOCACHE |
17 | #else |
18 | #define COMEDI_PAGE_PROTECTION PAGE_KERNEL |
19 | #endif |
20 | |
21 | static void comedi_buf_map_kref_release(struct kref *kref) |
22 | { |
23 | struct comedi_buf_map *bm = |
24 | container_of(kref, struct comedi_buf_map, refcount); |
25 | struct comedi_buf_page *buf; |
26 | unsigned int i; |
27 | |
28 | if (bm->page_list) { |
29 | if (bm->dma_dir != DMA_NONE) { |
30 | /* |
31 | * DMA buffer was allocated as a single block. |
32 | * Address is in page_list[0]. |
33 | */ |
34 | buf = &bm->page_list[0]; |
35 | dma_free_coherent(dev: bm->dma_hw_dev, |
36 | PAGE_SIZE * bm->n_pages, |
37 | cpu_addr: buf->virt_addr, dma_handle: buf->dma_addr); |
38 | } else { |
39 | for (i = 0; i < bm->n_pages; i++) { |
40 | buf = &bm->page_list[i]; |
41 | ClearPageReserved(virt_to_page(buf->virt_addr)); |
42 | free_page((unsigned long)buf->virt_addr); |
43 | } |
44 | } |
45 | vfree(addr: bm->page_list); |
46 | } |
47 | if (bm->dma_dir != DMA_NONE) |
48 | put_device(dev: bm->dma_hw_dev); |
49 | kfree(objp: bm); |
50 | } |
51 | |
52 | static void __comedi_buf_free(struct comedi_device *dev, |
53 | struct comedi_subdevice *s) |
54 | { |
55 | struct comedi_async *async = s->async; |
56 | struct comedi_buf_map *bm; |
57 | unsigned long flags; |
58 | |
59 | if (async->prealloc_buf) { |
60 | if (s->async_dma_dir == DMA_NONE) |
61 | vunmap(addr: async->prealloc_buf); |
62 | async->prealloc_buf = NULL; |
63 | async->prealloc_bufsz = 0; |
64 | } |
65 | |
66 | spin_lock_irqsave(&s->spin_lock, flags); |
67 | bm = async->buf_map; |
68 | async->buf_map = NULL; |
69 | spin_unlock_irqrestore(lock: &s->spin_lock, flags); |
70 | comedi_buf_map_put(bm); |
71 | } |
72 | |
73 | static struct comedi_buf_map * |
74 | comedi_buf_map_alloc(struct comedi_device *dev, enum dma_data_direction dma_dir, |
75 | unsigned int n_pages) |
76 | { |
77 | struct comedi_buf_map *bm; |
78 | struct comedi_buf_page *buf; |
79 | unsigned int i; |
80 | |
81 | bm = kzalloc(size: sizeof(*bm), GFP_KERNEL); |
82 | if (!bm) |
83 | return NULL; |
84 | |
85 | kref_init(kref: &bm->refcount); |
86 | bm->dma_dir = dma_dir; |
87 | if (bm->dma_dir != DMA_NONE) { |
88 | /* Need ref to hardware device to free buffer later. */ |
89 | bm->dma_hw_dev = get_device(dev: dev->hw_dev); |
90 | } |
91 | |
92 | bm->page_list = vzalloc(size: sizeof(*buf) * n_pages); |
93 | if (!bm->page_list) |
94 | goto err; |
95 | |
96 | if (bm->dma_dir != DMA_NONE) { |
97 | void *virt_addr; |
98 | dma_addr_t dma_addr; |
99 | |
100 | /* |
101 | * Currently, the DMA buffer needs to be allocated as a |
102 | * single block so that it can be mmap()'ed. |
103 | */ |
104 | virt_addr = dma_alloc_coherent(dev: bm->dma_hw_dev, |
105 | PAGE_SIZE * n_pages, dma_handle: &dma_addr, |
106 | GFP_KERNEL); |
107 | if (!virt_addr) |
108 | goto err; |
109 | |
110 | for (i = 0; i < n_pages; i++) { |
111 | buf = &bm->page_list[i]; |
112 | buf->virt_addr = virt_addr + (i << PAGE_SHIFT); |
113 | buf->dma_addr = dma_addr + (i << PAGE_SHIFT); |
114 | } |
115 | |
116 | bm->n_pages = i; |
117 | } else { |
118 | for (i = 0; i < n_pages; i++) { |
119 | buf = &bm->page_list[i]; |
120 | buf->virt_addr = (void *)get_zeroed_page(GFP_KERNEL); |
121 | if (!buf->virt_addr) |
122 | break; |
123 | |
124 | SetPageReserved(virt_to_page(buf->virt_addr)); |
125 | } |
126 | |
127 | bm->n_pages = i; |
128 | if (i < n_pages) |
129 | goto err; |
130 | } |
131 | |
132 | return bm; |
133 | |
134 | err: |
135 | comedi_buf_map_put(bm); |
136 | return NULL; |
137 | } |
138 | |
139 | static void __comedi_buf_alloc(struct comedi_device *dev, |
140 | struct comedi_subdevice *s, |
141 | unsigned int n_pages) |
142 | { |
143 | struct comedi_async *async = s->async; |
144 | struct page **pages = NULL; |
145 | struct comedi_buf_map *bm; |
146 | struct comedi_buf_page *buf; |
147 | unsigned long flags; |
148 | unsigned int i; |
149 | |
150 | if (!IS_ENABLED(CONFIG_HAS_DMA) && s->async_dma_dir != DMA_NONE) { |
151 | dev_err(dev->class_dev, |
152 | "dma buffer allocation not supported\n" ); |
153 | return; |
154 | } |
155 | |
156 | bm = comedi_buf_map_alloc(dev, dma_dir: s->async_dma_dir, n_pages); |
157 | if (!bm) |
158 | return; |
159 | |
160 | spin_lock_irqsave(&s->spin_lock, flags); |
161 | async->buf_map = bm; |
162 | spin_unlock_irqrestore(lock: &s->spin_lock, flags); |
163 | |
164 | if (bm->dma_dir != DMA_NONE) { |
165 | /* |
166 | * DMA buffer was allocated as a single block. |
167 | * Address is in page_list[0]. |
168 | */ |
169 | buf = &bm->page_list[0]; |
170 | async->prealloc_buf = buf->virt_addr; |
171 | } else { |
172 | pages = vmalloc(size: sizeof(struct page *) * n_pages); |
173 | if (!pages) |
174 | return; |
175 | |
176 | for (i = 0; i < n_pages; i++) { |
177 | buf = &bm->page_list[i]; |
178 | pages[i] = virt_to_page(buf->virt_addr); |
179 | } |
180 | |
181 | /* vmap the pages to prealloc_buf */ |
182 | async->prealloc_buf = vmap(pages, count: n_pages, VM_MAP, |
183 | COMEDI_PAGE_PROTECTION); |
184 | |
185 | vfree(addr: pages); |
186 | } |
187 | } |
188 | |
189 | void comedi_buf_map_get(struct comedi_buf_map *bm) |
190 | { |
191 | if (bm) |
192 | kref_get(kref: &bm->refcount); |
193 | } |
194 | |
195 | int comedi_buf_map_put(struct comedi_buf_map *bm) |
196 | { |
197 | if (bm) |
198 | return kref_put(kref: &bm->refcount, release: comedi_buf_map_kref_release); |
199 | return 1; |
200 | } |
201 | |
202 | /* helper for "access" vm operation */ |
203 | int comedi_buf_map_access(struct comedi_buf_map *bm, unsigned long offset, |
204 | void *buf, int len, int write) |
205 | { |
206 | unsigned int pgoff = offset_in_page(offset); |
207 | unsigned long pg = offset >> PAGE_SHIFT; |
208 | int done = 0; |
209 | |
210 | while (done < len && pg < bm->n_pages) { |
211 | int l = min_t(int, len - done, PAGE_SIZE - pgoff); |
212 | void *b = bm->page_list[pg].virt_addr + pgoff; |
213 | |
214 | if (write) |
215 | memcpy(b, buf, l); |
216 | else |
217 | memcpy(buf, b, l); |
218 | buf += l; |
219 | done += l; |
220 | pg++; |
221 | pgoff = 0; |
222 | } |
223 | return done; |
224 | } |
225 | |
226 | /* returns s->async->buf_map and increments its kref refcount */ |
227 | struct comedi_buf_map * |
228 | comedi_buf_map_from_subdev_get(struct comedi_subdevice *s) |
229 | { |
230 | struct comedi_async *async = s->async; |
231 | struct comedi_buf_map *bm = NULL; |
232 | unsigned long flags; |
233 | |
234 | if (!async) |
235 | return NULL; |
236 | |
237 | spin_lock_irqsave(&s->spin_lock, flags); |
238 | bm = async->buf_map; |
239 | /* only want it if buffer pages allocated */ |
240 | if (bm && bm->n_pages) |
241 | comedi_buf_map_get(bm); |
242 | else |
243 | bm = NULL; |
244 | spin_unlock_irqrestore(lock: &s->spin_lock, flags); |
245 | |
246 | return bm; |
247 | } |
248 | |
249 | bool comedi_buf_is_mmapped(struct comedi_subdevice *s) |
250 | { |
251 | struct comedi_buf_map *bm = s->async->buf_map; |
252 | |
253 | return bm && (kref_read(kref: &bm->refcount) > 1); |
254 | } |
255 | |
256 | int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s, |
257 | unsigned long new_size) |
258 | { |
259 | struct comedi_async *async = s->async; |
260 | |
261 | lockdep_assert_held(&dev->mutex); |
262 | |
263 | /* Round up new_size to multiple of PAGE_SIZE */ |
264 | new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK; |
265 | |
266 | /* if no change is required, do nothing */ |
267 | if (async->prealloc_buf && async->prealloc_bufsz == new_size) |
268 | return 0; |
269 | |
270 | /* deallocate old buffer */ |
271 | __comedi_buf_free(dev, s); |
272 | |
273 | /* allocate new buffer */ |
274 | if (new_size) { |
275 | unsigned int n_pages = new_size >> PAGE_SHIFT; |
276 | |
277 | __comedi_buf_alloc(dev, s, n_pages); |
278 | |
279 | if (!async->prealloc_buf) { |
280 | /* allocation failed */ |
281 | __comedi_buf_free(dev, s); |
282 | return -ENOMEM; |
283 | } |
284 | } |
285 | async->prealloc_bufsz = new_size; |
286 | |
287 | return 0; |
288 | } |
289 | |
290 | void comedi_buf_reset(struct comedi_subdevice *s) |
291 | { |
292 | struct comedi_async *async = s->async; |
293 | |
294 | async->buf_write_alloc_count = 0; |
295 | async->buf_write_count = 0; |
296 | async->buf_read_alloc_count = 0; |
297 | async->buf_read_count = 0; |
298 | |
299 | async->buf_write_ptr = 0; |
300 | async->buf_read_ptr = 0; |
301 | |
302 | async->cur_chan = 0; |
303 | async->scans_done = 0; |
304 | async->scan_progress = 0; |
305 | async->munge_chan = 0; |
306 | async->munge_count = 0; |
307 | async->munge_ptr = 0; |
308 | |
309 | async->events = 0; |
310 | } |
311 | |
312 | static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s) |
313 | { |
314 | struct comedi_async *async = s->async; |
315 | unsigned int free_end = async->buf_read_count + async->prealloc_bufsz; |
316 | |
317 | return free_end - async->buf_write_alloc_count; |
318 | } |
319 | |
320 | unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s) |
321 | { |
322 | struct comedi_async *async = s->async; |
323 | unsigned int free_end = async->buf_read_count + async->prealloc_bufsz; |
324 | |
325 | return free_end - async->buf_write_count; |
326 | } |
327 | |
328 | /** |
329 | * comedi_buf_write_alloc() - Reserve buffer space for writing |
330 | * @s: COMEDI subdevice. |
331 | * @nbytes: Maximum space to reserve in bytes. |
332 | * |
333 | * Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition |
334 | * data buffer associated with the subdevice. The amount reserved is limited |
335 | * by the space available. |
336 | * |
337 | * Return: The amount of space reserved in bytes. |
338 | */ |
339 | unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s, |
340 | unsigned int nbytes) |
341 | { |
342 | struct comedi_async *async = s->async; |
343 | unsigned int unalloc = comedi_buf_write_n_unalloc(s); |
344 | |
345 | if (nbytes > unalloc) |
346 | nbytes = unalloc; |
347 | |
348 | async->buf_write_alloc_count += nbytes; |
349 | |
350 | /* |
351 | * ensure the async buffer 'counts' are read and updated |
352 | * before we write data to the write-alloc'ed buffer space |
353 | */ |
354 | smp_mb(); |
355 | |
356 | return nbytes; |
357 | } |
358 | EXPORT_SYMBOL_GPL(comedi_buf_write_alloc); |
359 | |
360 | /* |
361 | * munging is applied to data by core as it passes between user |
362 | * and kernel space |
363 | */ |
364 | static unsigned int comedi_buf_munge(struct comedi_subdevice *s, |
365 | unsigned int num_bytes) |
366 | { |
367 | struct comedi_async *async = s->async; |
368 | unsigned int count = 0; |
369 | const unsigned int num_sample_bytes = comedi_bytes_per_sample(s); |
370 | |
371 | if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) { |
372 | async->munge_count += num_bytes; |
373 | return num_bytes; |
374 | } |
375 | |
376 | /* don't munge partial samples */ |
377 | num_bytes -= num_bytes % num_sample_bytes; |
378 | while (count < num_bytes) { |
379 | int block_size = num_bytes - count; |
380 | unsigned int buf_end; |
381 | |
382 | buf_end = async->prealloc_bufsz - async->munge_ptr; |
383 | if (block_size > buf_end) |
384 | block_size = buf_end; |
385 | |
386 | s->munge(s->device, s, |
387 | async->prealloc_buf + async->munge_ptr, |
388 | block_size, async->munge_chan); |
389 | |
390 | /* |
391 | * ensure data is munged in buffer before the |
392 | * async buffer munge_count is incremented |
393 | */ |
394 | smp_wmb(); |
395 | |
396 | async->munge_chan += block_size / num_sample_bytes; |
397 | async->munge_chan %= async->cmd.chanlist_len; |
398 | async->munge_count += block_size; |
399 | async->munge_ptr += block_size; |
400 | async->munge_ptr %= async->prealloc_bufsz; |
401 | count += block_size; |
402 | } |
403 | |
404 | return count; |
405 | } |
406 | |
407 | unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s) |
408 | { |
409 | struct comedi_async *async = s->async; |
410 | |
411 | return async->buf_write_alloc_count - async->buf_write_count; |
412 | } |
413 | |
414 | /** |
415 | * comedi_buf_write_free() - Free buffer space after it is written |
416 | * @s: COMEDI subdevice. |
417 | * @nbytes: Maximum space to free in bytes. |
418 | * |
419 | * Free up to @nbytes bytes of space previously reserved for writing in the |
420 | * COMEDI acquisition data buffer associated with the subdevice. The amount of |
421 | * space freed is limited to the amount that was reserved. The freed space is |
422 | * assumed to have been filled with sample data by the writer. |
423 | * |
424 | * If the samples in the freed space need to be "munged", do so here. The |
425 | * freed space becomes available for allocation by the reader. |
426 | * |
427 | * Return: The amount of space freed in bytes. |
428 | */ |
429 | unsigned int comedi_buf_write_free(struct comedi_subdevice *s, |
430 | unsigned int nbytes) |
431 | { |
432 | struct comedi_async *async = s->async; |
433 | unsigned int allocated = comedi_buf_write_n_allocated(s); |
434 | |
435 | if (nbytes > allocated) |
436 | nbytes = allocated; |
437 | |
438 | async->buf_write_count += nbytes; |
439 | async->buf_write_ptr += nbytes; |
440 | comedi_buf_munge(s, num_bytes: async->buf_write_count - async->munge_count); |
441 | if (async->buf_write_ptr >= async->prealloc_bufsz) |
442 | async->buf_write_ptr %= async->prealloc_bufsz; |
443 | |
444 | return nbytes; |
445 | } |
446 | EXPORT_SYMBOL_GPL(comedi_buf_write_free); |
447 | |
448 | /** |
449 | * comedi_buf_read_n_available() - Determine amount of readable buffer space |
450 | * @s: COMEDI subdevice. |
451 | * |
452 | * Determine the amount of readable buffer space in the COMEDI acquisition data |
453 | * buffer associated with the subdevice. The readable buffer space is that |
454 | * which has been freed by the writer and "munged" to the sample data format |
455 | * expected by COMEDI if necessary. |
456 | * |
457 | * Return: The amount of readable buffer space. |
458 | */ |
459 | unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s) |
460 | { |
461 | struct comedi_async *async = s->async; |
462 | unsigned int num_bytes; |
463 | |
464 | if (!async) |
465 | return 0; |
466 | |
467 | num_bytes = async->munge_count - async->buf_read_count; |
468 | |
469 | /* |
470 | * ensure the async buffer 'counts' are read before we |
471 | * attempt to read data from the buffer |
472 | */ |
473 | smp_rmb(); |
474 | |
475 | return num_bytes; |
476 | } |
477 | EXPORT_SYMBOL_GPL(comedi_buf_read_n_available); |
478 | |
479 | /** |
480 | * comedi_buf_read_alloc() - Reserve buffer space for reading |
481 | * @s: COMEDI subdevice. |
482 | * @nbytes: Maximum space to reserve in bytes. |
483 | * |
484 | * Reserve up to @nbytes bytes of previously written and "munged" buffer space |
485 | * for reading in the COMEDI acquisition data buffer associated with the |
486 | * subdevice. The amount reserved is limited to the space available. The |
487 | * reader can read from the reserved space and then free it. A reader is also |
488 | * allowed to read from the space before reserving it as long as it determines |
489 | * the amount of readable data available, but the space needs to be marked as |
490 | * reserved before it can be freed. |
491 | * |
492 | * Return: The amount of space reserved in bytes. |
493 | */ |
494 | unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s, |
495 | unsigned int nbytes) |
496 | { |
497 | struct comedi_async *async = s->async; |
498 | unsigned int available; |
499 | |
500 | available = async->munge_count - async->buf_read_alloc_count; |
501 | if (nbytes > available) |
502 | nbytes = available; |
503 | |
504 | async->buf_read_alloc_count += nbytes; |
505 | |
506 | /* |
507 | * ensure the async buffer 'counts' are read before we |
508 | * attempt to read data from the read-alloc'ed buffer space |
509 | */ |
510 | smp_rmb(); |
511 | |
512 | return nbytes; |
513 | } |
514 | EXPORT_SYMBOL_GPL(comedi_buf_read_alloc); |
515 | |
516 | static unsigned int comedi_buf_read_n_allocated(struct comedi_async *async) |
517 | { |
518 | return async->buf_read_alloc_count - async->buf_read_count; |
519 | } |
520 | |
521 | /** |
522 | * comedi_buf_read_free() - Free buffer space after it has been read |
523 | * @s: COMEDI subdevice. |
524 | * @nbytes: Maximum space to free in bytes. |
525 | * |
526 | * Free up to @nbytes bytes of buffer space previously reserved for reading in |
527 | * the COMEDI acquisition data buffer associated with the subdevice. The |
528 | * amount of space freed is limited to the amount that was reserved. |
529 | * |
530 | * The freed space becomes available for allocation by the writer. |
531 | * |
532 | * Return: The amount of space freed in bytes. |
533 | */ |
534 | unsigned int comedi_buf_read_free(struct comedi_subdevice *s, |
535 | unsigned int nbytes) |
536 | { |
537 | struct comedi_async *async = s->async; |
538 | unsigned int allocated; |
539 | |
540 | /* |
541 | * ensure data has been read out of buffer before |
542 | * the async read count is incremented |
543 | */ |
544 | smp_mb(); |
545 | |
546 | allocated = comedi_buf_read_n_allocated(async); |
547 | if (nbytes > allocated) |
548 | nbytes = allocated; |
549 | |
550 | async->buf_read_count += nbytes; |
551 | async->buf_read_ptr += nbytes; |
552 | async->buf_read_ptr %= async->prealloc_bufsz; |
553 | return nbytes; |
554 | } |
555 | EXPORT_SYMBOL_GPL(comedi_buf_read_free); |
556 | |
557 | static void comedi_buf_memcpy_to(struct comedi_subdevice *s, |
558 | const void *data, unsigned int num_bytes) |
559 | { |
560 | struct comedi_async *async = s->async; |
561 | unsigned int write_ptr = async->buf_write_ptr; |
562 | |
563 | while (num_bytes) { |
564 | unsigned int block_size; |
565 | |
566 | if (write_ptr + num_bytes > async->prealloc_bufsz) |
567 | block_size = async->prealloc_bufsz - write_ptr; |
568 | else |
569 | block_size = num_bytes; |
570 | |
571 | memcpy(async->prealloc_buf + write_ptr, data, block_size); |
572 | |
573 | data += block_size; |
574 | num_bytes -= block_size; |
575 | |
576 | write_ptr = 0; |
577 | } |
578 | } |
579 | |
580 | static void comedi_buf_memcpy_from(struct comedi_subdevice *s, |
581 | void *dest, unsigned int nbytes) |
582 | { |
583 | void *src; |
584 | struct comedi_async *async = s->async; |
585 | unsigned int read_ptr = async->buf_read_ptr; |
586 | |
587 | while (nbytes) { |
588 | unsigned int block_size; |
589 | |
590 | src = async->prealloc_buf + read_ptr; |
591 | |
592 | if (nbytes >= async->prealloc_bufsz - read_ptr) |
593 | block_size = async->prealloc_bufsz - read_ptr; |
594 | else |
595 | block_size = nbytes; |
596 | |
597 | memcpy(dest, src, block_size); |
598 | nbytes -= block_size; |
599 | dest += block_size; |
600 | read_ptr = 0; |
601 | } |
602 | } |
603 | |
604 | /** |
605 | * comedi_buf_write_samples() - Write sample data to COMEDI buffer |
606 | * @s: COMEDI subdevice. |
607 | * @data: Pointer to source samples. |
608 | * @nsamples: Number of samples to write. |
609 | * |
610 | * Write up to @nsamples samples to the COMEDI acquisition data buffer |
611 | * associated with the subdevice, mark it as written and update the |
612 | * acquisition scan progress. If there is not enough room for the specified |
613 | * number of samples, the number of samples written is limited to the number |
614 | * that will fit and the %COMEDI_CB_OVERFLOW event flag is set to cause the |
615 | * acquisition to terminate with an overrun error. Set the %COMEDI_CB_BLOCK |
616 | * event flag if any samples are written to cause waiting tasks to be woken |
617 | * when the event flags are processed. |
618 | * |
619 | * Return: The amount of data written in bytes. |
620 | */ |
621 | unsigned int comedi_buf_write_samples(struct comedi_subdevice *s, |
622 | const void *data, unsigned int nsamples) |
623 | { |
624 | unsigned int max_samples; |
625 | unsigned int nbytes; |
626 | |
627 | /* |
628 | * Make sure there is enough room in the buffer for all the samples. |
629 | * If not, clamp the nsamples to the number that will fit, flag the |
630 | * buffer overrun and add the samples that fit. |
631 | */ |
632 | max_samples = comedi_bytes_to_samples(s, nbytes: comedi_buf_write_n_unalloc(s)); |
633 | if (nsamples > max_samples) { |
634 | dev_warn(s->device->class_dev, "buffer overrun\n" ); |
635 | s->async->events |= COMEDI_CB_OVERFLOW; |
636 | nsamples = max_samples; |
637 | } |
638 | |
639 | if (nsamples == 0) |
640 | return 0; |
641 | |
642 | nbytes = comedi_buf_write_alloc(s, |
643 | comedi_samples_to_bytes(s, nsamples)); |
644 | comedi_buf_memcpy_to(s, data, num_bytes: nbytes); |
645 | comedi_buf_write_free(s, nbytes); |
646 | comedi_inc_scan_progress(s, num_bytes: nbytes); |
647 | s->async->events |= COMEDI_CB_BLOCK; |
648 | |
649 | return nbytes; |
650 | } |
651 | EXPORT_SYMBOL_GPL(comedi_buf_write_samples); |
652 | |
653 | /** |
654 | * comedi_buf_read_samples() - Read sample data from COMEDI buffer |
655 | * @s: COMEDI subdevice. |
656 | * @data: Pointer to destination. |
657 | * @nsamples: Maximum number of samples to read. |
658 | * |
659 | * Read up to @nsamples samples from the COMEDI acquisition data buffer |
660 | * associated with the subdevice, mark it as read and update the acquisition |
661 | * scan progress. Limit the number of samples read to the number available. |
662 | * Set the %COMEDI_CB_BLOCK event flag if any samples are read to cause waiting |
663 | * tasks to be woken when the event flags are processed. |
664 | * |
665 | * Return: The amount of data read in bytes. |
666 | */ |
667 | unsigned int comedi_buf_read_samples(struct comedi_subdevice *s, |
668 | void *data, unsigned int nsamples) |
669 | { |
670 | unsigned int max_samples; |
671 | unsigned int nbytes; |
672 | |
673 | /* clamp nsamples to the number of full samples available */ |
674 | max_samples = comedi_bytes_to_samples(s, |
675 | nbytes: comedi_buf_read_n_available(s)); |
676 | if (nsamples > max_samples) |
677 | nsamples = max_samples; |
678 | |
679 | if (nsamples == 0) |
680 | return 0; |
681 | |
682 | nbytes = comedi_buf_read_alloc(s, |
683 | comedi_samples_to_bytes(s, nsamples)); |
684 | comedi_buf_memcpy_from(s, dest: data, nbytes); |
685 | comedi_buf_read_free(s, nbytes); |
686 | comedi_inc_scan_progress(s, num_bytes: nbytes); |
687 | s->async->events |= COMEDI_CB_BLOCK; |
688 | |
689 | return nbytes; |
690 | } |
691 | EXPORT_SYMBOL_GPL(comedi_buf_read_samples); |
692 | |