drivers/staging/iio/ring_sw.c

   1 /* The industrial I/O simple minimally locked ring buffer.
   2  *
   3  * Copyright (c) 2008 Jonathan Cameron
   4  *
   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.
   8  */
   9
  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>
  15 #include <linux/sched.h>
  16 #include <linux/poll.h>
  17 #include "ring_sw.h"
  18 #include "trigger.h"
  19
  20 static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
  21                                                 int bytes_per_datum, int length)
  22 {
  23         if ((length == 0) || (bytes_per_datum == 0))
  24                 return -EINVAL;
  25         __iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
  26         ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC);
  27         ring->read_p = NULL;
  28         ring->write_p = NULL;
  29         ring->last_written_p = NULL;
  30         ring->half_p = NULL;
  31         return ring->data ? 0 : -ENOMEM;
  32 }
  33
  34 static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  35 {
  36         spin_lock_init(&ring->use_lock);
  37 }
  38
  39 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  40 {
  41         kfree(ring->data);
  42 }
  43
  44 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
  45 {
  46         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  47         spin_lock(&ring->use_lock);
  48         ring->use_count++;
  49         spin_unlock(&ring->use_lock);
  50 }
  51 EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
  52
  53 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
  54 {
  55         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  56         spin_lock(&ring->use_lock);
  57         ring->use_count--;
  58         spin_unlock(&ring->use_lock);
  59 }
  60 EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
  61
  62
  63 /* Ring buffer related functionality */
  64 /* Store to ring is typically called in the bh of a data ready interrupt handler
  65  * in the device driver */
  66 /* Lock always held if their is a chance this may be called */
  67 /* Only one of these per ring may run concurrently - enforced by drivers */
  68 static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
  69                                 unsigned char *data, s64 timestamp)
  70 {
  71         int ret = 0;
  72         unsigned char *temp_ptr, *change_test_ptr;
  73
  74         /* initial store */
  75         if (unlikely(ring->write_p == NULL)) {
  76                 ring->write_p = ring->data;
  77                 /* Doesn't actually matter if this is out of the set
  78                  * as long as the read pointer is valid before this
  79                  * passes it - guaranteed as set later in this function.
  80                  */
  81                 ring->half_p = ring->data - ring->buf.length*ring->buf.bytes_per_datum/2;
  82         }
  83         /* Copy data to where ever the current write pointer says */
  84         memcpy(ring->write_p, data, ring->buf.bytes_per_datum);
  85         barrier();
  86         /* Update the pointer used to get most recent value.
  87          * Always valid as either points to latest or second latest value.
  88          * Before this runs it is null and read attempts fail with -EAGAIN.
  89          */
  90         ring->last_written_p = ring->write_p;
  91         barrier();
  92         /* temp_ptr used to ensure we never have an invalid pointer
  93          * it may be slightly lagging, but never invalid
  94          */
  95         temp_ptr = ring->write_p + ring->buf.bytes_per_datum;
  96         /* End of ring, back to the beginning */
  97         if (temp_ptr == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
  98                 temp_ptr = ring->data;
  99         /* Update the write pointer
 100          * always valid as long as this is the only function able to write.
 101          * Care needed with smp systems to ensure more than one ring fill
 102          * is never scheduled.
 103          */
 104         ring->write_p = temp_ptr;
 105
 106         if (ring->read_p == NULL)
 107                 ring->read_p = ring->data;
 108         /* Buffer full - move the read pointer and create / escalate
 109          * ring event */
 110         /* Tricky case - if the read pointer moves before we adjust it.
 111          * Handle by not pushing if it has moved - may result in occasional
 112          * unnecessary buffer full events when it wasn't quite true.
 113          */
 114         else if (ring->write_p == ring->read_p) {
 115                 change_test_ptr = ring->read_p;
 116                 temp_ptr = change_test_ptr + ring->buf.bytes_per_datum;
 117                 if (temp_ptr
 118                     == ring->data + ring->buf.length*ring->buf.bytes_per_datum) {
 119                         temp_ptr = ring->data;
 120                 }
 121                 /* We are moving pointer on one because the ring is full.  Any
 122                  * change to the read pointer will be this or greater.
 123                  */
 124                 if (change_test_ptr == ring->read_p)
 125                         ring->read_p = temp_ptr;
 126         }
 127         /* investigate if our event barrier has been passed */
 128         /* There are definite 'issues' with this and chances of
 129          * simultaneous read */
 130         /* Also need to use loop count to ensure this only happens once */
 131         ring->half_p += ring->buf.bytes_per_datum;
 132         if (ring->half_p == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
 133                 ring->half_p = ring->data;
 134         if (ring->half_p == ring->read_p) {
 135                 ring->buf.stufftoread = true;
 136                 wake_up_interruptible(&ring->buf.pollq);
 137         }
 138         return ret;
 139 }
 140
 141 int iio_read_first_n_sw_rb(struct iio_ring_buffer *r,
 142                            size_t n, char __user *buf)
 143 {
 144         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 145
 146         u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
 147         u8 *data;
 148         int ret, max_copied, bytes_to_rip, dead_offset;
 149
 150         /* A userspace program has probably made an error if it tries to
 151          *  read something that is not a whole number of bpds.
 152          * Return an error.
 153          */
 154         if (n % ring->buf.bytes_per_datum) {
 155                 ret = -EINVAL;
 156                 printk(KERN_INFO "Ring buffer read request not whole number of"
 157                        "samples: Request bytes %zd, Current bytes per datum %d\n",
 158                        n, ring->buf.bytes_per_datum);
 159                 goto error_ret;
 160         }
 161         /* Limit size to whole of ring buffer */
 162         bytes_to_rip = min((size_t)(ring->buf.bytes_per_datum*ring->buf.length),
 163                            n);
 164
 165         data = kmalloc(bytes_to_rip, GFP_KERNEL);
 166         if (data == NULL) {
 167                 ret = -ENOMEM;
 168                 goto error_ret;
 169         }
 170
 171         /* build local copy */
 172         initial_read_p = ring->read_p;
 173         if (unlikely(initial_read_p == NULL)) { /* No data here as yet */
 174                 ret = 0;
 175                 goto error_free_data_cpy;
 176         }
 177
 178         initial_write_p = ring->write_p;
 179
 180         /* Need a consistent pair */
 181         while ((initial_read_p != ring->read_p)
 182                || (initial_write_p != ring->write_p)) {
 183                 initial_read_p = ring->read_p;
 184                 initial_write_p = ring->write_p;
 185         }
 186         if (initial_write_p == initial_read_p) {
 187                 /* No new data available.*/
 188                 ret = 0;
 189                 goto error_free_data_cpy;
 190         }
 191
 192         if (initial_write_p >= initial_read_p + bytes_to_rip) {
 193                 /* write_p is greater than necessary, all is easy */
 194                 max_copied = bytes_to_rip;
 195                 memcpy(data, initial_read_p, max_copied);
 196                 end_read_p = initial_read_p + max_copied;
 197         } else if (initial_write_p > initial_read_p) {
 198                 /*not enough data to cpy */
 199                 max_copied = initial_write_p - initial_read_p;
 200                 memcpy(data, initial_read_p, max_copied);
 201                 end_read_p = initial_write_p;
 202         } else {
 203                 /* going through 'end' of ring buffer */
 204                 max_copied = ring->data
 205                         + ring->buf.length*ring->buf.bytes_per_datum - initial_read_p;
 206                 memcpy(data, initial_read_p, max_copied);
 207                 /* possible we are done if we align precisely with end */
 208                 if (max_copied == bytes_to_rip)
 209                         end_read_p = ring->data;
 210                 else if (initial_write_p
 211                          > ring->data + bytes_to_rip - max_copied) {
 212                         /* enough data to finish */
 213                         memcpy(data + max_copied, ring->data,
 214                                bytes_to_rip - max_copied);
 215                         max_copied = bytes_to_rip;
 216                         end_read_p = ring->data + (bytes_to_rip - max_copied);
 217                 } else {  /* not enough data */
 218                         memcpy(data + max_copied, ring->data,
 219                                initial_write_p - ring->data);
 220                         max_copied += initial_write_p - ring->data;
 221                         end_read_p = initial_write_p;
 222                 }
 223         }
 224         /* Now to verify which section was cleanly copied - i.e. how far
 225          * read pointer has been pushed */
 226         current_read_p = ring->read_p;
 227
 228         if (initial_read_p <= current_read_p)
 229                 dead_offset = current_read_p - initial_read_p;
 230         else
 231                 dead_offset = ring->buf.length*ring->buf.bytes_per_datum
 232                         - (initial_read_p - current_read_p);
 233
 234         /* possible issue if the initial write has been lapped or indeed
 235          * the point we were reading to has been passed */
 236         /* No valid data read.
 237          * In this case the read pointer is already correct having been
 238          * pushed further than we would look. */
 239         if (max_copied - dead_offset < 0) {
 240                 ret = 0;
 241                 goto error_free_data_cpy;
 242         }
 243
 244         /* setup the next read position */
 245         /* Beware, this may fail due to concurrency fun and games.
 246          *  Possible that sufficient fill commands have run to push the read
 247          * pointer past where we would be after the rip. If this occurs, leave
 248          * it be.
 249          */
 250         /* Tricky - deal with loops */
 251
 252         while (ring->read_p != end_read_p)
 253                 ring->read_p = end_read_p;
 254
 255         ret = max_copied - dead_offset;
 256
 257         if (copy_to_user(buf, data + dead_offset, ret))  {
 258                 ret =  -EFAULT;
 259                 goto error_free_data_cpy;
 260         }
 261
 262         if (bytes_to_rip >= ring->buf.length*ring->buf.bytes_per_datum/2)
 263                 ring->buf.stufftoread = 0;
 264
 265 error_free_data_cpy:
 266         kfree(data);
 267 error_ret:
 268
 269         return ret;
 270 }
 271 EXPORT_SYMBOL(iio_read_first_n_sw_rb);
 272
 273 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
 274 {
 275         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 276         return iio_store_to_sw_ring(ring, data, timestamp);
 277 }
 278 EXPORT_SYMBOL(iio_store_to_sw_rb);
 279
 280 static int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
 281                                       unsigned char *data)
 282 {
 283         unsigned char *last_written_p_copy;
 284
 285         iio_mark_sw_rb_in_use(&ring->buf);
 286 again:
 287         barrier();
 288         last_written_p_copy = ring->last_written_p;
 289         barrier(); /*unnessecary? */
 290         /* Check there is anything here */
 291         if (last_written_p_copy == NULL)
 292                 return -EAGAIN;
 293         memcpy(data, last_written_p_copy, ring->buf.bytes_per_datum);
 294
 295         if (unlikely(ring->last_written_p != last_written_p_copy))
 296                 goto again;
 297
 298         iio_unmark_sw_rb_in_use(&ring->buf);
 299         return 0;
 300 }
 301
 302 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
 303                              unsigned char *data)
 304 {
 305         return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
 306 }
 307 EXPORT_SYMBOL(iio_read_last_from_sw_rb);
 308
 309 int iio_request_update_sw_rb(struct iio_ring_buffer *r)
 310 {
 311         int ret = 0;
 312         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 313
 314         r->stufftoread = false;
 315         spin_lock(&ring->use_lock);
 316         if (!ring->update_needed)
 317                 goto error_ret;
 318         if (ring->use_count) {
 319                 ret = -EAGAIN;
 320                 goto error_ret;
 321         }
 322         __iio_free_sw_ring_buffer(ring);
 323         ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
 324                                             ring->buf.length);
 325 error_ret:
 326         spin_unlock(&ring->use_lock);
 327         return ret;
 328 }
 329 EXPORT_SYMBOL(iio_request_update_sw_rb);
 330
 331 int iio_get_bytes_per_datum_sw_rb(struct iio_ring_buffer *r)
 332 {
 333         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 334         return ring->buf.bytes_per_datum;
 335 }
 336 EXPORT_SYMBOL(iio_get_bytes_per_datum_sw_rb);
 337
 338 int iio_set_bytes_per_datum_sw_rb(struct iio_ring_buffer *r, size_t bpd)
 339 {
 340         if (r->bytes_per_datum != bpd) {
 341                 r->bytes_per_datum = bpd;
 342                 if (r->access.mark_param_change)
 343                         r->access.mark_param_change(r);
 344         }
 345         return 0;
 346 }
 347 EXPORT_SYMBOL(iio_set_bytes_per_datum_sw_rb);
 348
 349 int iio_get_length_sw_rb(struct iio_ring_buffer *r)
 350 {
 351         return r->length;
 352 }
 353 EXPORT_SYMBOL(iio_get_length_sw_rb);
 354
 355 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
 356 {
 357         if (r->length != length) {
 358                 r->length = length;
 359                 if (r->access.mark_param_change)
 360                         r->access.mark_param_change(r);
 361         }
 362         return 0;
 363 }
 364 EXPORT_SYMBOL(iio_set_length_sw_rb);
 365
 366 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
 367 {
 368         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 369         ring->update_needed = true;
 370         return 0;
 371 }
 372 EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
 373
 374 static void iio_sw_rb_release(struct device *dev)
 375 {
 376         struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
 377         iio_ring_access_release(&r->dev);
 378         kfree(iio_to_sw_ring(r));
 379 }
 380
 381 static IIO_RING_ENABLE_ATTR;
 382 static IIO_RING_BYTES_PER_DATUM_ATTR;
 383 static IIO_RING_LENGTH_ATTR;
 384
 385 /* Standard set of ring buffer attributes */
 386 static struct attribute *iio_ring_attributes[] = {
 387         &dev_attr_length.attr,
 388         &dev_attr_bytes_per_datum.attr,
 389         &dev_attr_enable.attr,
 390         NULL,
 391 };
 392
 393 static struct attribute_group iio_ring_attribute_group = {
 394         .attrs = iio_ring_attributes,
 395 };
 396
 397 static const struct attribute_group *iio_ring_attribute_groups[] = {
 398         &iio_ring_attribute_group,
 399         NULL
 400 };
 401
 402 static struct device_type iio_sw_ring_type = {
 403         .release = iio_sw_rb_release,
 404         .groups = iio_ring_attribute_groups,
 405 };
 406
 407 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
 408 {
 409         struct iio_ring_buffer *buf;
 410         struct iio_sw_ring_buffer *ring;
 411
 412         ring = kzalloc(sizeof *ring, GFP_KERNEL);
 413         if (!ring)
 414                 return NULL;
 415         buf = &ring->buf;
 416         iio_ring_buffer_init(buf, indio_dev);
 417         __iio_init_sw_ring_buffer(ring);
 418         buf->dev.type = &iio_sw_ring_type;
 419         buf->dev.parent = &indio_dev->dev;
 420         dev_set_drvdata(&buf->dev, (void *)buf);
 421
 422         return buf;
 423 }
 424 EXPORT_SYMBOL(iio_sw_rb_allocate);
 425
 426 void iio_sw_rb_free(struct iio_ring_buffer *r)
 427 {
 428         if (r)
 429                 iio_put_ring_buffer(r);
 430 }
 431 EXPORT_SYMBOL(iio_sw_rb_free);
 432
 433 int iio_sw_ring_preenable(struct iio_dev *indio_dev)
 434 {
 435         struct iio_ring_buffer *ring = indio_dev->ring;
 436         size_t size;
 437         dev_dbg(&indio_dev->dev, "%s\n", __func__);
 438         /* Check if there are any scan elements enabled, if not fail*/
 439         if (!(ring->scan_count || ring->scan_timestamp))
 440                 return -EINVAL;
 441         if (ring->scan_timestamp)
 442                 if (ring->scan_count)
 443                         /* Timestamp (aligned to s64) and data */
 444                         size = (((ring->scan_count * ring->bpe)
 445                                         + sizeof(s64) - 1)
 446                                 & ~(sizeof(s64) - 1))
 447                                 + sizeof(s64);
 448                 else /* Timestamp only  */
 449                         size = sizeof(s64);
 450         else /* Data only */
 451                 size = ring->scan_count * ring->bpe;
 452         ring->access.set_bytes_per_datum(ring, size);
 453
 454         return 0;
 455 }
 456 EXPORT_SYMBOL(iio_sw_ring_preenable);
 457
 458 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s)
 459 {
 460         struct iio_sw_ring_helper_state *st
 461                 = container_of(work_s, struct iio_sw_ring_helper_state,
 462                         work_trigger_to_ring);
 463         struct iio_ring_buffer *ring = st->indio_dev->ring;
 464         int len = 0;
 465         size_t datasize = ring->access.get_bytes_per_datum(ring);
 466         char *data = kmalloc(datasize, GFP_KERNEL);
 467
 468         if (data == NULL) {
 469                 dev_err(st->indio_dev->dev.parent,
 470                         "memory alloc failed in ring bh");
 471                 return;
 472         }
 473
 474         if (ring->scan_count)
 475                 len = st->get_ring_element(st, data);
 476
 477           /* Guaranteed to be aligned with 8 byte boundary */
 478         if (ring->scan_timestamp)
 479                 *(s64 *)(((phys_addr_t)data + len
 480                                 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
 481                         = st->last_timestamp;
 482         ring->access.store_to(ring,
 483                         (u8 *)data,
 484                         st->last_timestamp);
 485
 486         iio_trigger_notify_done(st->indio_dev->trig);
 487         kfree(data);
 488
 489         return;
 490 }
 491 EXPORT_SYMBOL(iio_sw_trigger_bh_to_ring);
 492
 493 void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time)
 494 {       struct iio_sw_ring_helper_state *h
 495                 = iio_dev_get_devdata(indio_dev);
 496         h->last_timestamp = time;
 497         schedule_work(&h->work_trigger_to_ring);
 498 }
 499 EXPORT_SYMBOL(iio_sw_poll_func_th);
 500
 501 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
 502 MODULE_LICENSE("GPL");