drivers/staging/hv/ring_buffer.c

   1 /*
   2  *
   3  * Copyright (c) 2009, Microsoft Corporation.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along with
  15  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  16  * Place - Suite 330, Boston, MA 02111-1307 USA.
  17  *
  18  * Authors:
  19  *   Haiyang Zhang <haiyangz@microsoft.com>
  20  *   Hank Janssen  <hjanssen@microsoft.com>
  21  *
  22  */
  23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  24
  25 #include <linux/kernel.h>
  26 #include <linux/mm.h>
  27 #include "logging.h"
  28 #include "ring_buffer.h"
  29
  30
  31 /* #defines */
  32
  33
  34 /* Amount of space to write to */
  35 #define BYTES_AVAIL_TO_WRITE(r, w, z) ((w) >= (r)) ? ((z) - ((w) - (r))) : ((r) - (w))
  36
  37
  38 /*++
  39
  40 Name:
  41         get_ringbuffer_availbytes()
  42
  43 Description:
  44         Get number of bytes available to read and to write to
  45         for the specified ring buffer
  46
  47 --*/
  48 static inline void
  49 get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
  50                           u32 *read, u32 *write)
  51 {
  52         u32 read_loc, write_loc;
  53
  54         /* Capture the read/write indices before they changed */
  55         read_loc = rbi->ring_buffer->read_index;
  56         write_loc = rbi->ring_buffer->write_index;
  57
  58         *write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->ring_datasize);
  59         *read = rbi->ring_datasize - *write;
  60 }
  61
  62 /*++
  63
  64 Name:
  65         get_next_write_location()
  66
  67 Description:
  68         Get the next write location for the specified ring buffer
  69
  70 --*/
  71 static inline u32
  72 get_next_write_location(struct hv_ring_buffer_info *ring_info)
  73 {
  74         u32 next = ring_info->ring_buffer->write_index;
  75
  76         /* ASSERT(next < ring_info->RingDataSize); */
  77
  78         return next;
  79 }
  80
  81 /*++
  82
  83 Name:
  84         set_next_write_location()
  85
  86 Description:
  87         Set the next write location for the specified ring buffer
  88
  89 --*/
  90 static inline void
  91 set_next_write_location(struct hv_ring_buffer_info *ring_info,
  92                      u32 next_write_location)
  93 {
  94         ring_info->ring_buffer->write_index = next_write_location;
  95 }
  96
  97 /*++
  98
  99 Name:
 100         get_next_read_location()
 101
 102 Description:
 103         Get the next read location for the specified ring buffer
 104
 105 --*/
 106 static inline u32
 107 get_next_read_location(struct hv_ring_buffer_info *ring_info)
 108 {
 109         u32 next = ring_info->ring_buffer->read_index;
 110
 111         /* ASSERT(next < ring_info->RingDataSize); */
 112
 113         return next;
 114 }
 115
 116 /*++
 117
 118 Name:
 119         get_next_readlocation_withoffset()
 120
 121 Description:
 122         Get the next read location + offset for the specified ring buffer.
 123         This allows the caller to skip
 124
 125 --*/
 126 static inline u32
 127 get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
 128                                  u32 offset)
 129 {
 130         u32 next = ring_info->ring_buffer->read_index;
 131
 132         /* ASSERT(next < ring_info->RingDataSize); */
 133         next += offset;
 134         next %= ring_info->ring_datasize;
 135
 136         return next;
 137 }
 138
 139 /*++
 140
 141 Name:
 142         set_next_read_location()
 143
 144 Description:
 145         Set the next read location for the specified ring buffer
 146
 147 --*/
 148 static inline void
 149 set_next_read_location(struct hv_ring_buffer_info *ring_info,
 150                     u32 next_read_location)
 151 {
 152         ring_info->ring_buffer->read_index = next_read_location;
 153 }
 154
 155
 156 /*++
 157
 158 Name:
 159         get_ring_buffer()
 160
 161 Description:
 162         Get the start of the ring buffer
 163
 164 --*/
 165 static inline void *
 166 get_ring_buffer(struct hv_ring_buffer_info *ring_info)
 167 {
 168         return (void *)ring_info->ring_buffer->buffer;
 169 }
 170
 171
 172 /*++
 173
 174 Name:
 175         get_ring_buffersize()
 176
 177 Description:
 178         Get the size of the ring buffer
 179
 180 --*/
 181 static inline u32
 182 get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
 183 {
 184         return ring_info->ring_datasize;
 185 }
 186
 187 /*++
 188
 189 Name:
 190         get_ring_bufferindices()
 191
 192 Description:
 193         Get the read and write indices as u64 of the specified ring buffer
 194
 195 --*/
 196 static inline u64
 197 get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
 198 {
 199         return (u64)ring_info->ring_buffer->write_index << 32;
 200 }
 201
 202
 203 /*++
 204
 205 Name:
 206         dump_ring_info()
 207
 208 Description:
 209         Dump out to console the ring buffer info
 210
 211 --*/
 212 void dump_ring_info(struct hv_ring_buffer_info *ring_info, char *prefix)
 213 {
 214         u32 bytes_avail_towrite;
 215         u32 bytes_avail_toread;
 216
 217         get_ringbuffer_availbytes(ring_info,
 218         &bytes_avail_toread,
 219         &bytes_avail_towrite);
 220
 221         DPRINT(VMBUS,
 222                 DEBUG_RING_LVL,
 223                 "%s <<ringinfo %p buffer %p avail write %u "
 224                 "avail read %u read idx %u write idx %u>>",
 225                 prefix,
 226                 ring_info,
 227                 ring_info->ring_buffer->buffer,
 228                 bytes_avail_towrite,
 229                 bytes_avail_toread,
 230                 ring_info->ring_buffer->read_index,
 231                 ring_info->ring_buffer->write_index);
 232 }
 233
 234
 235 /* Internal routines */
 236
 237 static u32
 238 copyto_ringbuffer(
 239         struct hv_ring_buffer_info      *ring_info,
 240         u32                             start_write_offset,
 241         void                            *src,
 242         u32                             srclen);
 243
 244 static u32
 245 copyfrom_ringbuffer(
 246         struct hv_ring_buffer_info      *ring_info,
 247         void                            *dest,
 248         u32                             destlen,
 249         u32                             start_read_offset);
 250
 251
 252
 253 /*++
 254
 255 Name:
 256         ringbuffer_get_debuginfo()
 257
 258 Description:
 259         Get various debug metrics for the specified ring buffer
 260
 261 --*/
 262 void ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 263                             struct hv_ring_buffer_debug_info *debug_info)
 264 {
 265         u32 bytes_avail_towrite;
 266         u32 bytes_avail_toread;
 267
 268         if (ring_info->ring_buffer) {
 269                 get_ringbuffer_availbytes(ring_info,
 270                                         &bytes_avail_toread,
 271                                         &bytes_avail_towrite);
 272
 273                 debug_info->bytes_avail_toread = bytes_avail_toread;
 274                 debug_info->bytes_avail_towrite = bytes_avail_towrite;
 275                 debug_info->current_read_index =
 276                         ring_info->ring_buffer->read_index;
 277                 debug_info->current_write_index =
 278                         ring_info->ring_buffer->write_index;
 279                 debug_info->current_interrupt_mask =
 280                         ring_info->ring_buffer->interrupt_mask;
 281         }
 282 }
 283
 284
 285 /*++
 286
 287 Name:
 288         get_ringbuffer_interrupt_mask()
 289
 290 Description:
 291         Get the interrupt mask for the specified ring buffer
 292
 293 --*/
 294 u32 get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *rbi)
 295 {
 296         return rbi->ring_buffer->interrupt_mask;
 297 }
 298
 299 /*++
 300
 301 Name:
 302         hv_ringbuffer_init()
 303
 304 Description:
 305         Initialize the ring buffer
 306
 307 --*/
 308 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 309                    void *buffer, u32 buflen)
 310 {
 311         if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
 312                 return -EINVAL;
 313
 314         memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
 315
 316         ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
 317         ring_info->ring_buffer->read_index =
 318                 ring_info->ring_buffer->write_index = 0;
 319
 320         ring_info->ring_size = buflen;
 321         ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
 322
 323         spin_lock_init(&ring_info->ring_lock);
 324
 325         return 0;
 326 }
 327
 328 /*++
 329
 330 Name:
 331         hv_ringbuffer_cleanup()
 332
 333 Description:
 334         Cleanup the ring buffer
 335
 336 --*/
 337 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 338 {
 339 }
 340
 341 /*++
 342
 343 Name:
 344         hv_ringbuffer_write()
 345
 346 Description:
 347         Write to the ring buffer
 348
 349 --*/
 350 int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 351                     struct scatterlist *sglist, u32 sgcount)
 352 {
 353         int i = 0;
 354         u32 bytes_avail_towrite;
 355         u32 bytes_avail_toread;
 356         u32 totalbytes_towrite = 0;
 357
 358         struct scatterlist *sg;
 359         volatile u32 next_write_location;
 360         u64 prev_indices = 0;
 361         unsigned long flags;
 362
 363         for_each_sg(sglist, sg, sgcount, i)
 364         {
 365                 totalbytes_towrite += sg->length;
 366         }
 367
 368         totalbytes_towrite += sizeof(u64);
 369
 370         spin_lock_irqsave(&outring_info->ring_lock, flags);
 371
 372         get_ringbuffer_availbytes(outring_info,
 373                                 &bytes_avail_toread,
 374                                 &bytes_avail_towrite);
 375
 376         /* Dumpring_info(Outring_info, "BEFORE "); */
 377
 378         /* If there is only room for the packet, assume it is full. */
 379         /* Otherwise, the next time around, we think the ring buffer */
 380         /* is empty since the read index == write index */
 381         if (bytes_avail_towrite <= totalbytes_towrite) {
 382                 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 383                 return -1;
 384         }
 385
 386         /* Write to the ring buffer */
 387         next_write_location = get_next_write_location(outring_info);
 388
 389         for_each_sg(sglist, sg, sgcount, i)
 390         {
 391                 next_write_location = copyto_ringbuffer(outring_info,
 392                                                      next_write_location,
 393                                                      sg_virt(sg),
 394                                                      sg->length);
 395         }
 396
 397         /* Set previous packet start */
 398         prev_indices = get_ring_bufferindices(outring_info);
 399
 400         next_write_location = copyto_ringbuffer(outring_info,
 401                                              next_write_location,
 402                                              &prev_indices,
 403                                              sizeof(u64));
 404
 405         /* Make sure we flush all writes before updating the writeIndex */
 406         mb();
 407
 408         /* Now, update the write location */
 409         set_next_write_location(outring_info, next_write_location);
 410
 411         /* Dumpring_info(Outring_info, "AFTER "); */
 412
 413         spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 414         return 0;
 415 }
 416
 417
 418 /*++
 419
 420 Name:
 421         ringbuffer_peek()
 422
 423 Description:
 424         Read without advancing the read index
 425
 426 --*/
 427 int ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
 428                    void *Buffer, u32 buflen)
 429 {
 430         u32 bytes_avail_towrite;
 431         u32 bytes_avail_toread;
 432         u32 next_read_location = 0;
 433         unsigned long flags;
 434
 435         spin_lock_irqsave(&Inring_info->ring_lock, flags);
 436
 437         get_ringbuffer_availbytes(Inring_info,
 438                                 &bytes_avail_toread,
 439                                 &bytes_avail_towrite);
 440
 441         /* Make sure there is something to read */
 442         if (bytes_avail_toread < buflen) {
 443                 /* DPRINT_DBG(VMBUS,
 444                         "got callback but not enough to read "
 445                         "<avail to read %d read size %d>!!",
 446                         bytes_avail_toread,
 447                         BufferLen); */
 448
 449                 spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
 450
 451                 return -1;
 452         }
 453
 454         /* Convert to byte offset */
 455         next_read_location = get_next_read_location(Inring_info);
 456
 457         next_read_location = copyfrom_ringbuffer(Inring_info,
 458                                                 Buffer,
 459                                                 buflen,
 460                                                 next_read_location);
 461
 462         spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
 463
 464         return 0;
 465 }
 466
 467
 468 /*++
 469
 470 Name:
 471         ringbuffer_read()
 472
 473 Description:
 474         Read and advance the read index
 475
 476 --*/
 477 int ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 478                    u32 buflen, u32 offset)
 479 {
 480         u32 bytes_avail_towrite;
 481         u32 bytes_avail_toread;
 482         u32 next_read_location = 0;
 483         u64 prev_indices = 0;
 484         unsigned long flags;
 485
 486         if (buflen <= 0)
 487                 return -EINVAL;
 488
 489         spin_lock_irqsave(&inring_info->ring_lock, flags);
 490
 491         get_ringbuffer_availbytes(inring_info,
 492                                 &bytes_avail_toread,
 493                                 &bytes_avail_towrite);
 494
 495         /* Dumpring_info(Inring_info, "BEFORE "); */
 496
 497         /* Make sure there is something to read */
 498         if (bytes_avail_toread < buflen) {
 499                 spin_unlock_irqrestore(&inring_info->ring_lock, flags);
 500
 501                 return -1;
 502         }
 503
 504         next_read_location =
 505                 get_next_readlocation_withoffset(inring_info, offset);
 506
 507         next_read_location = copyfrom_ringbuffer(inring_info,
 508                                                 buffer,
 509                                                 buflen,
 510                                                 next_read_location);
 511
 512         next_read_location = copyfrom_ringbuffer(inring_info,
 513                                                 &prev_indices,
 514                                                 sizeof(u64),
 515                                                 next_read_location);
 516
 517         /* Make sure all reads are done before we update the read index since */
 518         /* the writer may start writing to the read area once the read index */
 519         /*is updated */
 520         mb();
 521
 522         /* Update the read index */
 523         set_next_read_location(inring_info, next_read_location);
 524
 525         /* Dumpring_info(Inring_info, "AFTER "); */
 526
 527         spin_unlock_irqrestore(&inring_info->ring_lock, flags);
 528
 529         return 0;
 530 }
 531
 532
 533 /*++
 534
 535 Name:
 536         copyto_ringbuffer()
 537
 538 Description:
 539         Helper routine to copy from source to ring buffer.
 540         Assume there is enough room. Handles wrap-around in dest case only!!
 541
 542 --*/
 543 static u32
 544 copyto_ringbuffer(
 545         struct hv_ring_buffer_info      *ring_info,
 546         u32                             start_write_offset,
 547         void                            *src,
 548         u32                             srclen)
 549 {
 550         void *ring_buffer = get_ring_buffer(ring_info);
 551         u32 ring_buffer_size = get_ring_buffersize(ring_info);
 552         u32 frag_len;
 553
 554         /* wrap-around detected! */
 555         if (srclen > ring_buffer_size - start_write_offset) {
 556                 frag_len = ring_buffer_size - start_write_offset;
 557                 memcpy(ring_buffer + start_write_offset, src, frag_len);
 558                 memcpy(ring_buffer, src + frag_len, srclen - frag_len);
 559         } else
 560                 memcpy(ring_buffer + start_write_offset, src, srclen);
 561
 562         start_write_offset += srclen;
 563         start_write_offset %= ring_buffer_size;
 564
 565         return start_write_offset;
 566 }
 567
 568
 569 /*++
 570
 571 Name:
 572         copyfrom_ringbuffer()
 573
 574 Description:
 575         Helper routine to copy to source from ring buffer.
 576         Assume there is enough room. Handles wrap-around in src case only!!
 577
 578 --*/
 579 static u32
 580 copyfrom_ringbuffer(
 581         struct hv_ring_buffer_info      *ring_info,
 582         void                            *dest,
 583         u32                             destlen,
 584         u32                             start_read_offset)
 585 {
 586         void *ring_buffer = get_ring_buffer(ring_info);
 587         u32 ring_buffer_size = get_ring_buffersize(ring_info);
 588
 589         u32 frag_len;
 590
 591         /* wrap-around detected at the src */
 592         if (destlen > ring_buffer_size - start_read_offset) {
 593                 frag_len = ring_buffer_size - start_read_offset;
 594
 595                 memcpy(dest, ring_buffer + start_read_offset, frag_len);
 596                 memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
 597         } else
 598
 599                 memcpy(dest, ring_buffer + start_read_offset, destlen);
 600
 601
 602         start_read_offset += destlen;
 603         start_read_offset %= ring_buffer_size;
 604
 605         return start_read_offset;
 606 }
 607
 608
 609 /* eof */