include/linux/kfifo.h

   1 /*
   2  * A generic kernel FIFO implementation.
   3  *
   4  * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
   5  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23 /*
  24  * Howto porting drivers to the new generic fifo API:
  25  *
  26  * - Modify the declaration of the "struct kfifo *" object into a
  27  *   in-place "struct kfifo" object
  28  * - Init the in-place object with kfifo_alloc() or kfifo_init()
  29  *   Note: The address of the in-place "struct kfifo" object must be
  30  *   passed as the first argument to this functions
  31  * - Replace the use of __kfifo_put into kfifo_in and __kfifo_get
  32  *   into kfifo_out
  33  * - Replace the use of kfifo_put into kfifo_in_locked and kfifo_get
  34  *   into kfifo_out_locked
  35  *   Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc
  36  *   must be passed now to the kfifo_in_locked and kfifo_out_locked
  37  *   as the last parameter.
  38  * - All formerly name __kfifo_* functions has been renamed into kfifo_*
  39  */
  40
  41 #ifndef _LINUX_KFIFO_H
  42 #define _LINUX_KFIFO_H
  43
  44 #include <linux/kernel.h>
  45 #include <linux/spinlock.h>
  46
  47 struct kfifo {
  48         unsigned char *buffer;  /* the buffer holding the data */
  49         unsigned int size;      /* the size of the allocated buffer */
  50         unsigned int in;        /* data is added at offset (in % size) */
  51         unsigned int out;       /* data is extracted from off. (out % size) */
  52 };
  53
  54 /*
  55  * Macros for declaration and initialization of the kfifo datatype
  56  */
  57
  58 /* helper macro */
  59 #define __kfifo_initializer(s, b) \
  60         (struct kfifo) { \
  61                 .size   = s, \
  62                 .in     = 0, \
  63                 .out    = 0, \
  64                 .buffer = b \
  65         }
  66
  67 /**
  68  * DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
  69  * @name: name of the declared kfifo datatype
  70  * @size: size of the fifo buffer
  71  *
  72  * Note1: the macro can be used inside struct or union declaration
  73  * Note2: the macro creates two objects:
  74  *  A kfifo object with the given name and a buffer for the kfifo
  75  *  object named name##kfifo_buffer
  76  */
  77 #define DECLARE_KFIFO(name, size) \
  78 union { \
  79         struct kfifo name; \
  80         unsigned char name##kfifo_buffer[size + sizeof(struct kfifo)]; \
  81 }
  82
  83 /**
  84  * INIT_KFIFO - Initialize a kfifo declared by DECLARE_KFIFO
  85  * @name: name of the declared kfifo datatype
  86  */
  87 #define INIT_KFIFO(name) \
  88         name = __kfifo_initializer(sizeof(name##kfifo_buffer) - \
  89                                 sizeof(struct kfifo), name##kfifo_buffer)
  90
  91 /**
  92  * DEFINE_KFIFO - macro to define and initialize a kfifo
  93  * @name: name of the declared kfifo datatype
  94  * @size: size of the fifo buffer
  95  *
  96  * Note1: the macro can be used for global and local kfifo data type variables
  97  * Note2: the macro creates two objects:
  98  *  A kfifo object with the given name and a buffer for the kfifo
  99  *  object named name##kfifo_buffer
 100  */
 101 #define DEFINE_KFIFO(name, size) \
 102         unsigned char name##kfifo_buffer[size]; \
 103         struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)
 104
 105 #undef __kfifo_initializer
 106
 107 extern void kfifo_init(struct kfifo *fifo, void *buffer,
 108                         unsigned int size);
 109 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
 110                         gfp_t gfp_mask);
 111 extern void kfifo_free(struct kfifo *fifo);
 112 extern unsigned int kfifo_in(struct kfifo *fifo,
 113                                 const void *from, unsigned int len);
 114 extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
 115                                 void *to, unsigned int len);
 116
 117 /**
 118  * kfifo_reset - removes the entire FIFO contents
 119  * @fifo: the fifo to be emptied.
 120  */
 121 static inline void kfifo_reset(struct kfifo *fifo)
 122 {
 123         fifo->in = fifo->out = 0;
 124 }
 125
 126 /**
 127  * kfifo_reset_out - skip FIFO contents
 128  * @fifo: the fifo to be emptied.
 129  */
 130 static inline void kfifo_reset_out(struct kfifo *fifo)
 131 {
 132         smp_mb();
 133         fifo->out = fifo->in;
 134 }
 135
 136 /**
 137  * kfifo_size - returns the size of the fifo in bytes
 138  * @fifo: the fifo to be used.
 139  */
 140 static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
 141 {
 142         return fifo->size;
 143 }
 144
 145 /**
 146  * kfifo_len - returns the number of used bytes in the FIFO
 147  * @fifo: the fifo to be used.
 148  */
 149 static inline unsigned int kfifo_len(struct kfifo *fifo)
 150 {
 151         register unsigned int   out;
 152
 153         out = fifo->out;
 154         smp_rmb();
 155         return fifo->in - out;
 156 }
 157
 158 /**
 159  * kfifo_is_empty - returns true if the fifo is empty
 160  * @fifo: the fifo to be used.
 161  */
 162 static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
 163 {
 164         return fifo->in == fifo->out;
 165 }
 166
 167 /**
 168  * kfifo_is_full - returns true if the fifo is full
 169  * @fifo: the fifo to be used.
 170  */
 171 static inline __must_check int kfifo_is_full(struct kfifo *fifo)
 172 {
 173         return kfifo_len(fifo) == kfifo_size(fifo);
 174 }
 175
 176 /**
 177  * kfifo_avail - returns the number of bytes available in the FIFO
 178  * @fifo: the fifo to be used.
 179  */
 180 static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
 181 {
 182         return kfifo_size(fifo) - kfifo_len(fifo);
 183 }
 184
 185 /**
 186  * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
 187  * @fifo: the fifo to be used.
 188  * @from: the data to be added.
 189  * @n: the length of the data to be added.
 190  * @lock: pointer to the spinlock to use for locking.
 191  *
 192  * This function copies at most @len bytes from the @from buffer into
 193  * the FIFO depending on the free space, and returns the number of
 194  * bytes copied.
 195  */
 196 static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
 197                 const void *from, unsigned int n, spinlock_t *lock)
 198 {
 199         unsigned long flags;
 200         unsigned int ret;
 201
 202         spin_lock_irqsave(lock, flags);
 203
 204         ret = kfifo_in(fifo, from, n);
 205
 206         spin_unlock_irqrestore(lock, flags);
 207
 208         return ret;
 209 }
 210
 211 /**
 212  * kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
 213  * @fifo: the fifo to be used.
 214  * @to: where the data must be copied.
 215  * @n: the size of the destination buffer.
 216  * @lock: pointer to the spinlock to use for locking.
 217  *
 218  * This function copies at most @len bytes from the FIFO into the
 219  * @to buffer and returns the number of copied bytes.
 220  */
 221 static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 222         void *to, unsigned int n, spinlock_t *lock)
 223 {
 224         unsigned long flags;
 225         unsigned int ret;
 226
 227         spin_lock_irqsave(lock, flags);
 228
 229         ret = kfifo_out(fifo, to, n);
 230
 231         spin_unlock_irqrestore(lock, flags);
 232
 233         return ret;
 234 }
 235
 236 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
 237
 238 extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo,
 239         const void __user *from, unsigned int n);
 240
 241 extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo,
 242         void __user *to, unsigned int n);
 243
 244 /*
 245  * __kfifo_add_out internal helper function for updating the out offset
 246  */
 247 static inline void __kfifo_add_out(struct kfifo *fifo,
 248                                 unsigned int off)
 249 {
 250         smp_mb();
 251         fifo->out += off;
 252 }
 253
 254 /*
 255  * __kfifo_add_in internal helper function for updating the in offset
 256  */
 257 static inline void __kfifo_add_in(struct kfifo *fifo,
 258                                 unsigned int off)
 259 {
 260         smp_wmb();
 261         fifo->in += off;
 262 }
 263
 264 /*
 265  * __kfifo_off internal helper function for calculating the index of a
 266  * given offeset
 267  */
 268 static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
 269 {
 270         return off & (fifo->size - 1);
 271 }
 272
 273 /*
 274  * __kfifo_peek_n internal helper function for determinate the length of
 275  * the next record in the fifo
 276  */
 277 static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
 278                                 unsigned int recsize)
 279 {
 280 #define __KFIFO_GET(fifo, off, shift) \
 281         ((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))
 282
 283         unsigned int l;
 284
 285         l = __KFIFO_GET(fifo, 0, 0);
 286
 287         if (--recsize)
 288                 l |= __KFIFO_GET(fifo, 1, 8);
 289
 290         return l;
 291 #undef  __KFIFO_GET
 292 }
 293
 294 /*
 295  * __kfifo_poke_n internal helper function for storing the length of
 296  * the next record into the fifo
 297  */
 298 static inline void __kfifo_poke_n(struct kfifo *fifo,
 299                         unsigned int recsize, unsigned int n)
 300 {
 301 #define __KFIFO_PUT(fifo, off, val, shift) \
 302                 ( \
 303                 (fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
 304                 (unsigned char)((val) >> (shift)) \
 305                 )
 306
 307         __KFIFO_PUT(fifo, 0, n, 0);
 308
 309         if (--recsize)
 310                 __KFIFO_PUT(fifo, 1, n, 8);
 311 #undef  __KFIFO_PUT
 312 }
 313
 314 /*
 315  * __kfifo_in_... internal functions for put date into the fifo
 316  * do not call it directly, use kfifo_in_rec() instead
 317  */
 318 extern unsigned int __kfifo_in_n(struct kfifo *fifo,
 319         const void *from, unsigned int n, unsigned int recsize);
 320
 321 extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
 322         const void *from, unsigned int n, unsigned int recsize);
 323
 324 static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
 325         const void *from, unsigned int n, unsigned int recsize)
 326 {
 327         unsigned int ret;
 328
 329         ret = __kfifo_in_n(fifo, from, n, recsize);
 330
 331         if (likely(ret == 0)) {
 332                 if (recsize)
 333                         __kfifo_poke_n(fifo, recsize, n);
 334                 __kfifo_add_in(fifo, n + recsize);
 335         }
 336         return ret;
 337 }
 338
 339 /**
 340  * kfifo_in_rec - puts some record data into the FIFO
 341  * @fifo: the fifo to be used.
 342  * @from: the data to be added.
 343  * @n: the length of the data to be added.
 344  * @recsize: size of record field
 345  *
 346  * This function copies @n bytes from the @from into the FIFO and returns
 347  * the number of bytes which cannot be copied.
 348  * A returned value greater than the @n value means that the record doesn't
 349  * fit into the buffer.
 350  *
 351  * Note that with only one concurrent reader and one concurrent
 352  * writer, you don't need extra locking to use these functions.
 353  */
 354 static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
 355         void *from, unsigned int n, unsigned int recsize)
 356 {
 357         if (!__builtin_constant_p(recsize))
 358                 return __kfifo_in_generic(fifo, from, n, recsize);
 359         return __kfifo_in_rec(fifo, from, n, recsize);
 360 }
 361
 362 /*
 363  * __kfifo_out_... internal functions for get date from the fifo
 364  * do not call it directly, use kfifo_out_rec() instead
 365  */
 366 extern unsigned int __kfifo_out_n(struct kfifo *fifo,
 367         void *to, unsigned int reclen, unsigned int recsize);
 368
 369 extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
 370         void *to, unsigned int n,
 371         unsigned int recsize, unsigned int *total);
 372
 373 static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
 374         void *to, unsigned int n, unsigned int recsize,
 375         unsigned int *total)
 376 {
 377         unsigned int l;
 378
 379         if (!recsize) {
 380                 l = n;
 381                 if (total)
 382                         *total = l;
 383         } else {
 384                 l = __kfifo_peek_n(fifo, recsize);
 385                 if (total)
 386                         *total = l;
 387                 if (n < l)
 388                         return l;
 389         }
 390
 391         return __kfifo_out_n(fifo, to, l, recsize);
 392 }
 393
 394 /**
 395  * kfifo_out_rec - gets some record data from the FIFO
 396  * @fifo: the fifo to be used.
 397  * @to: where the data must be copied.
 398  * @n: the size of the destination buffer.
 399  * @recsize: size of record field
 400  * @total: pointer where the total number of to copied bytes should stored
 401  *
 402  * This function copies at most @n bytes from the FIFO to @to and returns the
 403  * number of bytes which cannot be copied.
 404  * A returned value greater than the @n value means that the record doesn't
 405  * fit into the @to buffer.
 406  *
 407  * Note that with only one concurrent reader and one concurrent
 408  * writer, you don't need extra locking to use these functions.
 409  */
 410 static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
 411         void *to, unsigned int n, unsigned int recsize,
 412         unsigned int *total)
 413
 414 {
 415         if (!__builtin_constant_p(recsize))
 416                 return __kfifo_out_generic(fifo, to, n, recsize, total);
 417         return __kfifo_out_rec(fifo, to, n, recsize, total);
 418 }
 419
 420 /*
 421  * __kfifo_from_user_... internal functions for transfer from user space into
 422  * the fifo. do not call it directly, use kfifo_from_user_rec() instead
 423  */
 424 extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 425         const void __user *from, unsigned int n, unsigned int recsize);
 426
 427 extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 428         const void __user *from, unsigned int n, unsigned int recsize);
 429
 430 static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
 431         const void __user *from, unsigned int n, unsigned int recsize)
 432 {
 433         unsigned int ret;
 434
 435         ret = __kfifo_from_user_n(fifo, from, n, recsize);
 436
 437         if (likely(ret == 0)) {
 438                 if (recsize)
 439                         __kfifo_poke_n(fifo, recsize, n);
 440                 __kfifo_add_in(fifo, n + recsize);
 441         }
 442         return ret;
 443 }
 444
 445 /**
 446  * kfifo_from_user_rec - puts some data from user space into the FIFO
 447  * @fifo: the fifo to be used.
 448  * @from: pointer to the data to be added.
 449  * @n: the length of the data to be added.
 450  * @recsize: size of record field
 451  *
 452  * This function copies @n bytes from the @from into the
 453  * FIFO and returns the number of bytes which cannot be copied.
 454  *
 455  * If the returned value is equal or less the @n value, the copy_from_user()
 456  * functions has failed. Otherwise the record doesn't fit into the buffer.
 457  *
 458  * Note that with only one concurrent reader and one concurrent
 459  * writer, you don't need extra locking to use these functions.
 460  */
 461 static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
 462         const void __user *from, unsigned int n, unsigned int recsize)
 463 {
 464         if (!__builtin_constant_p(recsize))
 465                 return __kfifo_from_user_generic(fifo, from, n, recsize);
 466         return __kfifo_from_user_rec(fifo, from, n, recsize);
 467 }
 468
 469 /*
 470  * __kfifo_to_user_... internal functions for transfer fifo data into user space
 471  * do not call it directly, use kfifo_to_user_rec() instead
 472  */
 473 extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 474         void __user *to, unsigned int n, unsigned int reclen,
 475         unsigned int recsize);
 476
 477 extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 478         void __user *to, unsigned int n, unsigned int recsize,
 479         unsigned int *total);
 480
 481 static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
 482         void __user *to, unsigned int n,
 483         unsigned int recsize, unsigned int *total)
 484 {
 485         unsigned int l;
 486
 487         if (!recsize) {
 488                 l = n;
 489                 if (total)
 490                         *total = l;
 491         } else {
 492                 l = __kfifo_peek_n(fifo, recsize);
 493                 if (total)
 494                         *total = l;
 495                 if (n < l)
 496                         return l;
 497         }
 498
 499         return __kfifo_to_user_n(fifo, to, n, l, recsize);
 500 }
 501
 502 /**
 503  * kfifo_to_user_rec - gets data from the FIFO and write it to user space
 504  * @fifo: the fifo to be used.
 505  * @to: where the data must be copied.
 506  * @n: the size of the destination buffer.
 507  * @recsize: size of record field
 508  * @total: pointer where the total number of to copied bytes should stored
 509  *
 510  * This function copies at most @n bytes from the FIFO to the @to.
 511  * In case of an error, the function returns the number of bytes which cannot
 512  * be copied.
 513  * If the returned value is equal or less the @n value, the copy_to_user()
 514  * functions has failed. Otherwise the record doesn't fit into the @to buffer.
 515  *
 516  * Note that with only one concurrent reader and one concurrent
 517  * writer, you don't need extra locking to use these functions.
 518  */
 519 static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
 520                 void __user *to, unsigned int n, unsigned int recsize,
 521                 unsigned int *total)
 522 {
 523         if (!__builtin_constant_p(recsize))
 524                 return __kfifo_to_user_generic(fifo, to, n, recsize, total);
 525         return __kfifo_to_user_rec(fifo, to, n, recsize, total);
 526 }
 527
 528 /*
 529  * __kfifo_peek_... internal functions for peek into the next fifo record
 530  * do not call it directly, use kfifo_peek_rec() instead
 531  */
 532 extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
 533                                 unsigned int recsize);
 534
 535 /**
 536  * kfifo_peek_rec - gets the size of the next FIFO record data
 537  * @fifo: the fifo to be used.
 538  * @recsize: size of record field
 539  *
 540  * This function returns the size of the next FIFO record in number of bytes
 541  */
 542 static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
 543         unsigned int recsize)
 544 {
 545         if (!__builtin_constant_p(recsize))
 546                 return __kfifo_peek_generic(fifo, recsize);
 547         if (!recsize)
 548                 return kfifo_len(fifo);
 549         return __kfifo_peek_n(fifo, recsize);
 550 }
 551
 552 /*
 553  * __kfifo_skip_... internal functions for skip the next fifo record
 554  * do not call it directly, use kfifo_skip_rec() instead
 555  */
 556 extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);
 557
 558 static inline void __kfifo_skip_rec(struct kfifo *fifo,
 559         unsigned int recsize)
 560 {
 561         unsigned int l;
 562
 563         if (recsize) {
 564                 l = __kfifo_peek_n(fifo, recsize);
 565
 566                 if (l + recsize <= kfifo_len(fifo)) {
 567                         __kfifo_add_out(fifo, l + recsize);
 568                         return;
 569                 }
 570         }
 571         kfifo_reset_out(fifo);
 572 }
 573
 574 /**
 575  * kfifo_skip_rec - skip the next fifo out record
 576  * @fifo: the fifo to be used.
 577  * @recsize: size of record field
 578  *
 579  * This function skips the next FIFO record
 580  */
 581 static inline void kfifo_skip_rec(struct kfifo *fifo,
 582         unsigned int recsize)
 583 {
 584         if (!__builtin_constant_p(recsize))
 585                 __kfifo_skip_generic(fifo, recsize);
 586         else
 587                 __kfifo_skip_rec(fifo, recsize);
 588 }
 589
 590 /**
 591  * kfifo_avail_rec - returns the number of bytes available in a record FIFO
 592  * @fifo: the fifo to be used.
 593  * @recsize: size of record field
 594  */
 595 static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
 596         unsigned int recsize)
 597 {
 598         unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);
 599
 600         return (l > recsize) ? l - recsize : 0;
 601 }
 602
 603 #endif