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 "ring_sw.h"
  16 #include "trigger.h"
  17
  18 static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
  19                                                 int bytes_per_datum, int length)
  20 {
  21         if ((length == 0) || (bytes_per_datum == 0))
  22                 return -EINVAL;
  23         __iio_update_ring_buffer(&ring->buf, bytes_per_datum, length);
  24         ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC);
  25         ring->read_p = NULL;
  26         ring->write_p = NULL;
  27         ring->last_written_p = NULL;
  28         ring->half_p = NULL;
  29         return ring->data ? 0 : -ENOMEM;
  30 }
  31
  32 static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  33 {
  34         spin_lock_init(&ring->use_lock);
  35 }
  36
  37 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
  38 {
  39         kfree(ring->data);
  40 }
  41
  42 void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
  43 {
  44         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  45         spin_lock(&ring->use_lock);
  46         ring->use_count++;
  47         spin_unlock(&ring->use_lock);
  48 }
  49 EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
  50
  51 void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
  52 {
  53         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
  54         spin_lock(&ring->use_lock);
  55         ring->use_count--;
  56         spin_unlock(&ring->use_lock);
  57 }
  58 EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
  59
  60
  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)
  68 {
  69         int ret = 0;
  70         int code;
  71         unsigned char *temp_ptr, *change_test_ptr;
  72
  73         /* initial store */
  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.
  79                  */
  80                 ring->half_p = ring->data - ring->buf.length*ring->buf.bytes_per_datum/2;
  81         }
  82         /* Copy data to where ever the current write pointer says */
  83         memcpy(ring->write_p, data, ring->buf.bytes_per_datum);
  84         barrier();
  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.
  88          */
  89         ring->last_written_p = ring->write_p;
  90         barrier();
  91         /* temp_ptr used to ensure we never have an invalid pointer
  92          * it may be slightly lagging, but never invalid
  93          */
  94         temp_ptr = ring->write_p + ring->buf.bytes_per_datum;
  95         /* End of ring, back to the beginning */
  96         if (temp_ptr == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
  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.
 102          */
 103         ring->write_p = temp_ptr;
 104
 105         if (ring->read_p == NULL)
 106                 ring->read_p = ring->data;
 107         /* Buffer full - move the read pointer and create / escalate
 108          * ring event */
 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.
 112          */
 113         else if (ring->write_p == ring->read_p) {
 114                 change_test_ptr = ring->read_p;
 115                 temp_ptr = change_test_ptr + ring->buf.bytes_per_datum;
 116                 if (temp_ptr
 117                     == ring->data + ring->buf.length*ring->buf.bytes_per_datum) {
 118                         temp_ptr = ring->data;
 119                 }
 120                 /* We are moving pointer on one because the ring is full.  Any
 121                  * change to the read pointer will be this or greater.
 122                  */
 123                 if (change_test_ptr == ring->read_p)
 124                         ring->read_p = temp_ptr;
 125
 126                 spin_lock(&ring->buf.shared_ev_pointer.lock);
 127
 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);
 131                 if (ret)
 132                         goto error_ret;
 133         }
 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.bytes_per_datum;
 139         if (ring->half_p == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
 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,
 145                                        code,
 146                                        timestamp,
 147                                        &ring->buf.shared_ev_pointer);
 148                 spin_unlock(&ring->buf.shared_ev_pointer.lock);
 149         }
 150 error_ret:
 151         return ret;
 152 }
 153
 154 int iio_rip_sw_rb(struct iio_ring_buffer *r,
 155                   size_t count, u8 **data, int *dead_offset)
 156 {
 157         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 158
 159         u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
 160         int ret, max_copied;
 161         int bytes_to_rip;
 162
 163         /* A userspace program has probably made an error if it tries to
 164          *  read something that is not a whole number of bpds.
 165          * Return an error.
 166          */
 167         if (count % ring->buf.bytes_per_datum) {
 168                 ret = -EINVAL;
 169                 printk(KERN_INFO "Ring buffer read request not whole number of"
 170                        "samples: Request bytes %zd, Current bytes per datum %d\n",
 171                        count, ring->buf.bytes_per_datum);
 172                 goto error_ret;
 173         }
 174         /* Limit size to whole of ring buffer */
 175         bytes_to_rip = min((size_t)(ring->buf.bytes_per_datum*ring->buf.length), count);
 176
 177         *data = kmalloc(bytes_to_rip, GFP_KERNEL);
 178         if (*data == NULL) {
 179                 ret = -ENOMEM;
 180                 goto error_ret;
 181         }
 182
 183         /* build local copy */
 184         initial_read_p = ring->read_p;
 185         if (unlikely(initial_read_p == NULL)) { /* No data here as yet */
 186                 ret = 0;
 187                 goto error_free_data_cpy;
 188         }
 189
 190         initial_write_p = ring->write_p;
 191
 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;
 197         }
 198         if (initial_write_p == initial_read_p) {
 199                 /* No new data available.*/
 200                 ret = 0;
 201                 goto error_free_data_cpy;
 202         }
 203
 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;
 214         } else {
 215                 /* going through 'end' of ring buffer */
 216                 max_copied = ring->data
 217                         + ring->buf.length*ring->buf.bytes_per_datum - 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;
 234                 }
 235         }
 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;
 239
 240         if (initial_read_p <= current_read_p)
 241                 *dead_offset = current_read_p - initial_read_p;
 242         else
 243                 *dead_offset = ring->buf.length*ring->buf.bytes_per_datum
 244                         - (initial_read_p - current_read_p);
 245
 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) {
 252                 ret = 0;
 253                 goto error_free_data_cpy;
 254         }
 255
 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
 260          * it be.
 261          */
 262         /* Tricky - deal with loops */
 263
 264         while (ring->read_p != end_read_p)
 265                 ring->read_p = end_read_p;
 266
 267         return max_copied - *dead_offset;
 268
 269 error_free_data_cpy:
 270         kfree(*data);
 271 error_ret:
 272         return ret;
 273 }
 274 EXPORT_SYMBOL(iio_rip_sw_rb);
 275
 276 int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
 277 {
 278         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 279         return iio_store_to_sw_ring(ring, data, timestamp);
 280 }
 281 EXPORT_SYMBOL(iio_store_to_sw_rb);
 282
 283 static int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
 284                                       unsigned char *data)
 285 {
 286         unsigned char *last_written_p_copy;
 287
 288         iio_mark_sw_rb_in_use(&ring->buf);
 289 again:
 290         barrier();
 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)
 295                 return -EAGAIN;
 296         memcpy(data, last_written_p_copy, ring->buf.bytes_per_datum);
 297
 298         if (unlikely(ring->last_written_p != last_written_p_copy))
 299                 goto again;
 300
 301         iio_unmark_sw_rb_in_use(&ring->buf);
 302         return 0;
 303 }
 304
 305 int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
 306                              unsigned char *data)
 307 {
 308         return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
 309 }
 310 EXPORT_SYMBOL(iio_read_last_from_sw_rb);
 311
 312 int iio_request_update_sw_rb(struct iio_ring_buffer *r)
 313 {
 314         int ret = 0;
 315         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 316
 317         spin_lock(&ring->use_lock);
 318         if (!ring->update_needed)
 319                 goto error_ret;
 320         if (ring->use_count) {
 321                 ret = -EAGAIN;
 322                 goto error_ret;
 323         }
 324         __iio_free_sw_ring_buffer(ring);
 325         ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
 326                                             ring->buf.length);
 327 error_ret:
 328         spin_unlock(&ring->use_lock);
 329         return ret;
 330 }
 331 EXPORT_SYMBOL(iio_request_update_sw_rb);
 332
 333 int iio_get_bytes_per_datum_sw_rb(struct iio_ring_buffer *r)
 334 {
 335         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 336         return ring->buf.bytes_per_datum;
 337 }
 338 EXPORT_SYMBOL(iio_get_bytes_per_datum_sw_rb);
 339
 340 int iio_set_bytes_per_datum_sw_rb(struct iio_ring_buffer *r, size_t bpd)
 341 {
 342         if (r->bytes_per_datum != bpd) {
 343                 r->bytes_per_datum = bpd;
 344                 if (r->access.mark_param_change)
 345                         r->access.mark_param_change(r);
 346         }
 347         return 0;
 348 }
 349 EXPORT_SYMBOL(iio_set_bytes_per_datum_sw_rb);
 350
 351 int iio_get_length_sw_rb(struct iio_ring_buffer *r)
 352 {
 353         return r->length;
 354 }
 355 EXPORT_SYMBOL(iio_get_length_sw_rb);
 356
 357 int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
 358 {
 359         if (r->length != length) {
 360                 r->length = length;
 361                 if (r->access.mark_param_change)
 362                         r->access.mark_param_change(r);
 363         }
 364         return 0;
 365 }
 366 EXPORT_SYMBOL(iio_set_length_sw_rb);
 367
 368 int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
 369 {
 370         struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 371         ring->update_needed = true;
 372         return 0;
 373 }
 374 EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
 375
 376 static void iio_sw_rb_release(struct device *dev)
 377 {
 378         struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
 379         kfree(iio_to_sw_ring(r));
 380 }
 381
 382 static IIO_RING_ENABLE_ATTR;
 383 static IIO_RING_BYTES_PER_DATUM_ATTR;
 384 static IIO_RING_LENGTH_ATTR;
 385
 386 /* Standard set of ring buffer attributes */
 387 static struct attribute *iio_ring_attributes[] = {
 388         &dev_attr_length.attr,
 389         &dev_attr_bytes_per_datum.attr,
 390         &dev_attr_enable.attr,
 391         NULL,
 392 };
 393
 394 static struct attribute_group iio_ring_attribute_group = {
 395         .attrs = iio_ring_attributes,
 396 };
 397
 398 static const struct attribute_group *iio_ring_attribute_groups[] = {
 399         &iio_ring_attribute_group,
 400         NULL
 401 };
 402
 403 static struct device_type iio_sw_ring_type = {
 404         .release = iio_sw_rb_release,
 405         .groups = iio_ring_attribute_groups,
 406 };
 407
 408 struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
 409 {
 410         struct iio_ring_buffer *buf;
 411         struct iio_sw_ring_buffer *ring;
 412
 413         ring = kzalloc(sizeof *ring, GFP_KERNEL);
 414         if (!ring)
 415                 return NULL;
 416         buf = &ring->buf;
 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);
 424
 425         return buf;
 426 }
 427 EXPORT_SYMBOL(iio_sw_rb_allocate);
 428
 429 void iio_sw_rb_free(struct iio_ring_buffer *r)
 430 {
 431         if (r)
 432                 iio_put_ring_buffer(r);
 433 }
 434 EXPORT_SYMBOL(iio_sw_rb_free);
 435
 436 int iio_sw_ring_preenable(struct iio_dev *indio_dev)
 437 {
 438         struct iio_ring_buffer *ring = indio_dev->ring;
 439         size_t size;
 440         dev_dbg(&indio_dev->dev, "%s\n", __func__);
 441         /* Check if there are any scan elements enabled, if not fail*/
 442         if (!(ring->scan_count || ring->scan_timestamp))
 443                 return -EINVAL;
 444         if (ring->scan_timestamp)
 445                 if (ring->scan_count)
 446                         /* Timestamp (aligned to s64) and data */
 447                         size = (((ring->scan_count * ring->bpe)
 448                                         + sizeof(s64) - 1)
 449                                 & ~(sizeof(s64) - 1))
 450                                 + sizeof(s64);
 451                 else /* Timestamp only  */
 452                         size = sizeof(s64);
 453         else /* Data only */
 454                 size = ring->scan_count * ring->bpe;
 455         ring->access.set_bytes_per_datum(ring, size);
 456
 457         return 0;
 458 }
 459 EXPORT_SYMBOL(iio_sw_ring_preenable);
 460
 461 void iio_sw_trigger_bh_to_ring(struct work_struct *work_s)
 462 {
 463         struct iio_sw_ring_helper_state *st
 464                 = container_of(work_s, struct iio_sw_ring_helper_state,
 465                         work_trigger_to_ring);
 466         struct iio_ring_buffer *ring = st->indio_dev->ring;
 467         int len = 0;
 468         size_t datasize = ring->access.get_bytes_per_datum(ring);
 469         char *data = kmalloc(datasize, GFP_KERNEL);
 470
 471         if (data == NULL) {
 472                 dev_err(st->indio_dev->dev.parent,
 473                         "memory alloc failed in ring bh");
 474                 return;
 475         }
 476
 477         if (ring->scan_count)
 478                 len = st->get_ring_element(st, data);
 479
 480           /* Guaranteed to be aligned with 8 byte boundary */
 481         if (ring->scan_timestamp)
 482                 *(s64 *)(((phys_addr_t)data + len
 483                                 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
 484                         = st->last_timestamp;
 485         ring->access.store_to(ring,
 486                         (u8 *)data,
 487                         st->last_timestamp);
 488
 489         iio_trigger_notify_done(st->indio_dev->trig);
 490         kfree(data);
 491
 492         return;
 493 }
 494 EXPORT_SYMBOL(iio_sw_trigger_bh_to_ring);
 495
 496 void iio_sw_poll_func_th(struct iio_dev *indio_dev, s64 time)
 497 {       struct iio_sw_ring_helper_state *h
 498                 = iio_dev_get_devdata(indio_dev);
 499         h->last_timestamp = time;
 500         schedule_work(&h->work_trigger_to_ring);
 501 }
 502 EXPORT_SYMBOL(iio_sw_poll_func_th);
 503
 504 MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
 505 MODULE_LICENSE("GPL");