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/poll.h>
  16 #include "ring_sw.h"
  17 #include "trigger.h"
  18
  19 static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
  20                                                 int bytes_per_datum, int length)
  21 {
  22         if ((length == 0) || (bytes_per_datum == 0))
  23                 return -EINVAL;
  24         __iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
  25         ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC);
  26         ring->read_p = NULL;
  27         ring->write_p = NULL;
  28         ring->last_written_p = NULL;
  29         ring->half_p = NULL;
  30         return ring->data ? 0 : -ENOMEM;
  31 }
  32
  33 static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  34 {
  35         spin_lock_init(&ring->use_lock);
  36 }
  37
  38 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  39 {
  40         kfree(ring->data);
  41 }
  42
  43 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
  44 {
  45         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  46         spin_lock(&ring->use_lock);
  47         ring->use_count++;
  48         spin_unlock(&ring->use_lock);
  49 }
  50 EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
  51
  52 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
  53 {
  54         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  55         spin_lock(&ring->use_lock);
  56         ring->use_count--;
  57         spin_unlock(&ring->use_lock);
  58 }
  59 EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
  60
  61
  62 /* Ring buffer related functionality */
  63 /* Store to ring is typically called in the bh of a data ready interrupt handler
  64  * in the device driver */
  65 /* Lock always held if their is a chance this may be called */
  66 /* Only one of these per ring may run concurrently - enforced by drivers */
  67 static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
  68                                 unsigned char *data, s64 timestamp)
  69 {
  70         int ret = 0;
  71         int code;
  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                 spin_lock(&ring->buf.shared_ev_pointer.lock);
 128
 129                 ret = iio_push_or_escallate_ring_event(&ring->buf,
 130                                IIO_EVENT_CODE_RING_100_FULL, timestamp);
 131                 spin_unlock(&ring->buf.shared_ev_pointer.lock);
 132                 if (ret)
 133                         goto error_ret;
 134         }
 135         /* investigate if our event barrier has been passed */
 136         /* There are definite 'issues' with this and chances of
 137          * simultaneous read */
 138         /* Also need to use loop count to ensure this only happens once */
 139         ring->half_p += ring->buf.bytes_per_datum;
 140         if (ring->half_p == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
 141                 ring->half_p = ring->data;
 142         if (ring->half_p == ring->read_p) {
 143                 spin_lock(&ring->buf.shared_ev_pointer.lock);
 144                 code = IIO_EVENT_CODE_RING_50_FULL;
 145                 ret = __iio_push_event(&ring->buf.ev_int,
 146                                        code,
 147                                        timestamp,
 148                                        &ring->buf.shared_ev_pointer);
 149                 spin_unlock(&ring->buf.shared_ev_pointer.lock);
 150         }
 151 error_ret:
 152         return ret;
 153 }
 154
 155 int iio_rip_sw_rb(struct iio_ring_buffer *r,
 156                   size_t count, char __user *buf, int *dead_offset)
 157 {
 158         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 159
 160         u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
 161         u8 *data;
 162         int ret, max_copied;
 163         int bytes_to_rip;
 164
 165         /* A userspace program has probably made an error if it tries to
 166          *  read something that is not a whole number of bpds.
 167          * Return an error.
 168          */
 169         if (count % ring->buf.bytes_per_datum) {
 170                 ret = -EINVAL;
 171                 printk(KERN_INFO "Ring buffer read request not whole number of"
 172                        "samples: Request bytes %zd, Current bytes per datum %d\n",
 173                        count, ring->buf.bytes_per_datum);
 174                 goto error_ret;
 175         }
 176         /* Limit size to whole of ring buffer */
 177         bytes_to_rip = min((size_t)(ring->buf.bytes_per_datum*ring->buf.length), count);
 178
 179         data = kmalloc(bytes_to_rip, GFP_KERNEL);
 180         if (data == NULL) {
 181                 ret = -ENOMEM;
 182                 goto error_ret;
 183         }
 184
 185         /* build local copy */
 186         initial_read_p = ring->read_p;
 187         if (unlikely(initial_read_p == NULL)) { /* No data here as yet */
 188                 ret = 0;
 189                 goto error_free_data_cpy;
 190         }
 191
 192         initial_write_p = ring->write_p;
 193
 194         /* Need a consistent pair */
 195         while ((initial_read_p != ring->read_p)
 196                || (initial_write_p != ring->write_p)) {
 197                 initial_read_p = ring->read_p;
 198                 initial_write_p = ring->write_p;
 199         }
 200         if (initial_write_p == initial_read_p) {
 201                 /* No new data available.*/
 202                 ret = 0;
 203                 goto error_free_data_cpy;
 204         }
 205
 206         if (initial_write_p >= initial_read_p + bytes_to_rip) {
 207                 /* write_p is greater than necessary, all is easy */
 208                 max_copied = bytes_to_rip;
 209                 memcpy(data, initial_read_p, max_copied);
 210                 end_read_p = initial_read_p + max_copied;
 211         } else if (initial_write_p > initial_read_p) {
 212                 /*not enough data to cpy */
 213                 max_copied = initial_write_p - initial_read_p;
 214                 memcpy(data, initial_read_p, max_copied);
 215                 end_read_p = initial_write_p;
 216         } else {
 217                 /* going through 'end' of ring buffer */
 218                 max_copied = ring->data
 219                         + ring->buf.length*ring->buf.bytes_per_datum - initial_read_p;
 220                 memcpy(data, initial_read_p, max_copied);
 221                 /* possible we are done if we align precisely with end */
 222                 if (max_copied == bytes_to_rip)
 223                         end_read_p = ring->data;
 224                 else if (initial_write_p
 225                          > ring->data + bytes_to_rip - max_copied) {
 226                         /* enough data to finish */
 227                         memcpy(data + max_copied, ring->data,
 228                                bytes_to_rip - max_copied);
 229                         max_copied = bytes_to_rip;
 230                         end_read_p = ring->data + (bytes_to_rip - max_copied);
 231                 } else {  /* not enough data */
 232                         memcpy(data + max_copied, ring->data,
 233                                initial_write_p - ring->data);
 234                         max_copied += initial_write_p - ring->data;
 235                         end_read_p = initial_write_p;
 236                 }
 237         }
 238         /* Now to verify which section was cleanly copied - i.e. how far
 239          * read pointer has been pushed */
 240         current_read_p = ring->read_p;
 241
 242         if (initial_read_p <= current_read_p)
 243                 *dead_offset = current_read_p - initial_read_p;
 244         else
 245                 *dead_offset = ring->buf.length*ring->buf.bytes_per_datum
 246                         - (initial_read_p - current_read_p);
 247
 248         /* possible issue if the initial write has been lapped or indeed
 249          * the point we were reading to has been passed */
 250         /* No valid data read.
 251          * In this case the read pointer is already correct having been
 252          * pushed further than we would look. */
 253         if (max_copied - *dead_offset < 0) {
 254                 ret = 0;
 255                 goto error_free_data_cpy;
 256         }
 257
 258         /* setup the next read position */
 259         /* Beware, this may fail due to concurrency fun and games.
 260          *  Possible that sufficient fill commands have run to push the read
 261          * pointer past where we would be after the rip. If this occurs, leave
 262          * it be.
 263          */
 264         /* Tricky - deal with loops */
 265
 266         while (ring->read_p != end_read_p)
 267                 ring->read_p = end_read_p;
 268
 269         ret = max_copied - *dead_offset;
 270
 271         if (copy_to_user(buf, data + *dead_offset, ret))  {
 272                 ret =  -EFAULT;
 273                 goto error_free_data_cpy;
 274         }
 275 error_free_data_cpy:
 276         kfree(data);
 277 error_ret:
 278
 279         return ret;
 280 }
 281 EXPORT_SYMBOL(iio_rip_sw_rb);
 282
 283 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
 284 {
 285         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 286         return iio_store_to_sw_ring(ring, data, timestamp);
 287 }
 288 EXPORT_SYMBOL(iio_store_to_sw_rb);
 289
 290 static int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
 291                                       unsigned char *data)
 292 {
 293         unsigned char *last_written_p_copy;
 294
 295         iio_mark_sw_rb_in_use(&ring->buf);
 296 again:
 297         barrier();
 298         last_written_p_copy = ring->last_written_p;
 299         barrier(); /*unnessecary? */
 300         /* Check there is anything here */
 301         if (last_written_p_copy == NULL)
 302                 return -EAGAIN;
 303         memcpy(data, last_written_p_copy, ring->buf.bytes_per_datum);
 304
 305         if (unlikely(ring->last_written_p != last_written_p_copy))
 306                 goto again;
 307
 308         iio_unmark_sw_rb_in_use(&ring->buf);
 309         return 0;
 310 }
 311
 312 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
 313                              unsigned char *data)
 314 {
 315         return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
 316 }
 317 EXPORT_SYMBOL(iio_read_last_from_sw_rb);
 318
 319 int iio_request_update_sw_rb(struct iio_ring_buffer *r)
 320 {
 321         int ret = 0;
 322         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 323
 324         spin_lock(&ring->use_lock);
 325         if (!ring->update_needed)
 326                 goto error_ret;
 327         if (ring->use_count) {
 328                 ret = -EAGAIN;
 329                 goto error_ret;
 330         }
 331         __iio_free_sw_ring_buffer(ring);
 332         ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
 333                                             ring->buf.length);
 334 error_ret:
 335         spin_unlock(&ring->use_lock);
 336         return ret;
 337 }
 338 EXPORT_SYMBOL(iio_request_update_sw_rb);
 339
 340 int iio_get_bytes_per_datum_sw_rb(struct iio_ring_buffer *r)
 341 {
 342         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 343         return ring->buf.bytes_per_datum;
 344 }
 345 EXPORT_SYMBOL(iio_get_bytes_per_datum_sw_rb);
 346
 347 int iio_set_bytes_per_datum_sw_rb(struct iio_ring_buffer *r, size_t bpd)
 348 {
 349         if (r->bytes_per_datum != bpd) {
 350                 r->bytes_per_datum = bpd;
 351                 if (r->access.mark_param_change)
 352                         r->access.mark_param_change(r);
 353         }
 354         return 0;
 355 }
 356 EXPORT_SYMBOL(iio_set_bytes_per_datum_sw_rb);
 357
 358 int iio_get_length_sw_rb(struct iio_ring_buffer *r)
 359 {
 360         return r->length;
 361 }
 362 EXPORT_SYMBOL(iio_get_length_sw_rb);
 363
 364 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
 365 {
 366         if (r->length != length) {
 367                 r->length = length;
 368                 if (r->access.mark_param_change)
 369                         r->access.mark_param_change(r);
 370         }
 371         return 0;
 372 }
 373 EXPORT_SYMBOL(iio_set_length_sw_rb);
 374
 375 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
 376 {
 377         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 378         ring->update_needed = true;
 379         return 0;
 380 }
 381 EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
 382
 383 static void iio_sw_rb_release(struct device *dev)
 384 {
 385         struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
 386         kfree(iio_to_sw_ring(r));
 387 }
 388
 389 static IIO_RING_ENABLE_ATTR;
 390 static IIO_RING_BYTES_PER_DATUM_ATTR;
 391 static IIO_RING_LENGTH_ATTR;
 392
 393 /* Standard set of ring buffer attributes */
 394 static struct attribute *iio_ring_attributes[] = {
 395         &dev_attr_length.attr,
 396         &dev_attr_bytes_per_datum.attr,
 397         &dev_attr_enable.attr,
 398         NULL,
 399 };
 400
 401 static struct attribute_group iio_ring_attribute_group = {
 402         .attrs = iio_ring_attributes,
 403 };
 404
 405 static const struct attribute_group *iio_ring_attribute_groups[] = {
 406         &iio_ring_attribute_group,
 407         NULL
 408 };
 409
 410 static struct device_type iio_sw_ring_type = {
 411         .release = iio_sw_rb_release,
 412         .groups = iio_ring_attribute_groups,
 413 };
 414
 415 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
 416 {
 417         struct iio_ring_buffer *buf;
 418         struct iio_sw_ring_buffer *ring;
 419
 420         ring = kzalloc(sizeof *ring, GFP_KERNEL);
 421         if (!ring)
 422                 return NULL;
 423         buf = &ring->buf;
 424         iio_ring_buffer_init(buf, indio_dev);
 425         __iio_init_sw_ring_buffer(ring);
 426         buf->dev.type = &iio_sw_ring_type;
 427         device_initialize(&buf->dev);
 428         buf->dev.parent = &indio_dev->dev;
 429         buf->dev.bus = &iio_bus_type;
 430         dev_set_drvdata(&buf->dev, (void *)buf);
 431
 432         return buf;
 433 }
 434 EXPORT_SYMBOL(iio_sw_rb_allocate);
 435
 436 void iio_sw_rb_free(struct iio_ring_buffer *r)
 437 {
 438         if (r)
 439                 iio_put_ring_buffer(r);
 440 }
 441 EXPORT_SYMBOL(iio_sw_rb_free);
 442
 443 int iio_sw_ring_preenable(struct iio_dev *indio_dev)
 444 {
 445         struct iio_ring_buffer *ring = indio_dev->ring;
 446         size_t size;
 447         dev_dbg(&indio_dev->dev, "%s\n", __func__);
 448         /* Check if there are any scan elements enabled, if not fail*/
 449         if (!(ring->scan_count || ring->scan_timestamp))
 450                 return -EINVAL;
 451         if (ring->scan_timestamp)
 452                 if (ring->scan_count)
 453                         /* Timestamp (aligned to s64) and data */
 454                         size = (((ring->scan_count * ring->bpe)
 455                                         + sizeof(s64) - 1)
 456                                 & ~(sizeof(s64) - 1))
 457                                 + sizeof(s64);
 458                 else /* Timestamp only  */
 459                         size = sizeof(s64);
 460         else /* Data only */
 461                 size = ring->scan_count * ring->bpe;
 462         ring->access.set_bytes_per_datum(ring, size);
 463
 464         return 0;
 465 }
 466 EXPORT_SYMBOL(iio_sw_ring_preenable);
 467
 468 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s)
 469 {
 470         struct iio_sw_ring_helper_state *st
 471                 = container_of(work_s, struct iio_sw_ring_helper_state,
 472                         work_trigger_to_ring);
 473         struct iio_ring_buffer *ring = st->indio_dev->ring;
 474         int len = 0;
 475         size_t datasize = ring->access.get_bytes_per_datum(ring);
 476         char *data = kmalloc(datasize, GFP_KERNEL);
 477
 478         if (data == NULL) {
 479                 dev_err(st->indio_dev->dev.parent,
 480                         "memory alloc failed in ring bh");
 481                 return;
 482         }
 483
 484         if (ring->scan_count)
 485                 len = st->get_ring_element(st, data);
 486
 487           /* Guaranteed to be aligned with 8 byte boundary */
 488         if (ring->scan_timestamp)
 489                 *(s64 *)(((phys_addr_t)data + len
 490                                 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
 491                         = st->last_timestamp;
 492         ring->access.store_to(ring,
 493                         (u8 *)data,
 494                         st->last_timestamp);
 495
 496         iio_trigger_notify_done(st->indio_dev->trig);
 497         kfree(data);
 498
 499         return;
 500 }
 501 EXPORT_SYMBOL(iio_sw_trigger_bh_to_ring);
 502
 503 void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time)
 504 {       struct iio_sw_ring_helper_state *h
 505                 = iio_dev_get_devdata(indio_dev);
 506         h->last_timestamp = time;
 507         schedule_work(&h->work_trigger_to_ring);
 508 }
 509 EXPORT_SYMBOL(iio_sw_poll_func_th);
 510
 511 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
 512 MODULE_LICENSE("GPL");