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. Must be a power of two.
  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. Must be a power of two.
  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 extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
 117                                 void *to, unsigned int len, unsigned offset);
 118
 119 /**
 120  * kfifo_initialized - Check if kfifo is initialized.
 121  * @fifo: fifo to check
 122  * Return %true if FIFO is initialized, otherwise %false.
 123  * Assumes the fifo was 0 before.
 124  */
 125 static inline bool kfifo_initialized(struct kfifo *fifo)
 126 {
 127         return fifo->buffer != NULL;
 128 }
 129
 130 /**
 131  * kfifo_reset - removes the entire FIFO contents
 132  * @fifo: the fifo to be emptied.
 133  */
 134 static inline void kfifo_reset(struct kfifo *fifo)
 135 {
 136         fifo->in = fifo->out = 0;
 137 }
 138
 139 /**
 140  * kfifo_reset_out - skip FIFO contents
 141  * @fifo: the fifo to be emptied.
 142  */
 143 static inline void kfifo_reset_out(struct kfifo *fifo)
 144 {
 145         smp_mb();
 146         fifo->out = fifo->in;
 147 }
 148
 149 /**
 150  * kfifo_size - returns the size of the fifo in bytes
 151  * @fifo: the fifo to be used.
 152  */
 153 static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
 154 {
 155         return fifo->size;
 156 }
 157
 158 /**
 159  * kfifo_len - returns the number of used bytes in the FIFO
 160  * @fifo: the fifo to be used.
 161  */
 162 static inline unsigned int kfifo_len(struct kfifo *fifo)
 163 {
 164         register unsigned int   out;
 165
 166         out = fifo->out;
 167         smp_rmb();
 168         return fifo->in - out;
 169 }
 170
 171 /**
 172  * kfifo_is_empty - returns true if the fifo is empty
 173  * @fifo: the fifo to be used.
 174  */
 175 static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
 176 {
 177         return fifo->in == fifo->out;
 178 }
 179
 180 /**
 181  * kfifo_is_full - returns true if the fifo is full
 182  * @fifo: the fifo to be used.
 183  */
 184 static inline __must_check int kfifo_is_full(struct kfifo *fifo)
 185 {
 186         return kfifo_len(fifo) == kfifo_size(fifo);
 187 }
 188
 189 /**
 190  * kfifo_avail - returns the number of bytes available in the FIFO
 191  * @fifo: the fifo to be used.
 192  */
 193 static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
 194 {
 195         return kfifo_size(fifo) - kfifo_len(fifo);
 196 }
 197
 198 /**
 199  * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
 200  * @fifo: the fifo to be used.
 201  * @from: the data to be added.
 202  * @n: the length of the data to be added.
 203  * @lock: pointer to the spinlock to use for locking.
 204  *
 205  * This function copies at most @len bytes from the @from buffer into
 206  * the FIFO depending on the free space, and returns the number of
 207  * bytes copied.
 208  */
 209 static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
 210                 const void *from, unsigned int n, spinlock_t *lock)
 211 {
 212         unsigned long flags;
 213         unsigned int ret;
 214
 215         spin_lock_irqsave(lock, flags);
 216
 217         ret = kfifo_in(fifo, from, n);
 218
 219         spin_unlock_irqrestore(lock, flags);
 220
 221         return ret;
 222 }
 223
 224 /**
 225  * kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
 226  * @fifo: the fifo to be used.
 227  * @to: where the data must be copied.
 228  * @n: the size of the destination buffer.
 229  * @lock: pointer to the spinlock to use for locking.
 230  *
 231  * This function copies at most @len bytes from the FIFO into the
 232  * @to buffer and returns the number of copied bytes.
 233  */
 234 static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 235         void *to, unsigned int n, spinlock_t *lock)
 236 {
 237         unsigned long flags;
 238         unsigned int ret;
 239
 240         spin_lock_irqsave(lock, flags);
 241
 242         ret = kfifo_out(fifo, to, n);
 243
 244         spin_unlock_irqrestore(lock, flags);
 245
 246         return ret;
 247 }
 248
 249 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
 250
 251 extern __must_check int kfifo_from_user(struct kfifo *fifo,
 252         const void __user *from, unsigned int n, unsigned *lenout);
 253
 254 extern __must_check int kfifo_to_user(struct kfifo *fifo,
 255         void __user *to, unsigned int n, unsigned *lenout);
 256
 257 /*
 258  * __kfifo_add_out internal helper function for updating the out offset
 259  */
 260 static inline void __kfifo_add_out(struct kfifo *fifo,
 261                                 unsigned int off)
 262 {
 263         smp_mb();
 264         fifo->out += off;
 265 }
 266
 267 /*
 268  * __kfifo_add_in internal helper function for updating the in offset
 269  */
 270 static inline void __kfifo_add_in(struct kfifo *fifo,
 271                                 unsigned int off)
 272 {
 273         smp_wmb();
 274         fifo->in += off;
 275 }
 276
 277 /*
 278  * __kfifo_off internal helper function for calculating the index of a
 279  * given offeset
 280  */
 281 static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
 282 {
 283         return off & (fifo->size - 1);
 284 }
 285
 286 /*
 287  * __kfifo_peek_n internal helper function for determinate the length of
 288  * the next record in the fifo
 289  */
 290 static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
 291                                 unsigned int recsize)
 292 {
 293 #define __KFIFO_GET(fifo, off, shift) \
 294         ((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))
 295
 296         unsigned int l;
 297
 298         l = __KFIFO_GET(fifo, 0, 0);
 299
 300         if (--recsize)
 301                 l |= __KFIFO_GET(fifo, 1, 8);
 302
 303         return l;
 304 #undef  __KFIFO_GET
 305 }
 306
 307 /*
 308  * __kfifo_poke_n internal helper function for storing the length of
 309  * the next record into the fifo
 310  */
 311 static inline void __kfifo_poke_n(struct kfifo *fifo,
 312                         unsigned int recsize, unsigned int n)
 313 {
 314 #define __KFIFO_PUT(fifo, off, val, shift) \
 315                 ( \
 316                 (fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
 317                 (unsigned char)((val) >> (shift)) \
 318                 )
 319
 320         __KFIFO_PUT(fifo, 0, n, 0);
 321
 322         if (--recsize)
 323                 __KFIFO_PUT(fifo, 1, n, 8);
 324 #undef  __KFIFO_PUT
 325 }
 326
 327 /*
 328  * __kfifo_in_... internal functions for put date into the fifo
 329  * do not call it directly, use kfifo_in_rec() instead
 330  */
 331 extern unsigned int __kfifo_in_n(struct kfifo *fifo,
 332         const void *from, unsigned int n, unsigned int recsize);
 333
 334 extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
 335         const void *from, unsigned int n, unsigned int recsize);
 336
 337 static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
 338         const void *from, unsigned int n, unsigned int recsize)
 339 {
 340         unsigned int ret;
 341
 342         ret = __kfifo_in_n(fifo, from, n, recsize);
 343
 344         if (likely(ret == 0)) {
 345                 if (recsize)
 346                         __kfifo_poke_n(fifo, recsize, n);
 347                 __kfifo_add_in(fifo, n + recsize);
 348         }
 349         return ret;
 350 }
 351
 352 /**
 353  * kfifo_in_rec - puts some record data into the FIFO
 354  * @fifo: the fifo to be used.
 355  * @from: the data to be added.
 356  * @n: the length of the data to be added.
 357  * @recsize: size of record field
 358  *
 359  * This function copies @n bytes from the @from into the FIFO and returns
 360  * the number of bytes which cannot be copied.
 361  * A returned value greater than the @n value means that the record doesn't
 362  * fit into the buffer.
 363  *
 364  * Note that with only one concurrent reader and one concurrent
 365  * writer, you don't need extra locking to use these functions.
 366  */
 367 static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
 368         void *from, unsigned int n, unsigned int recsize)
 369 {
 370         if (!__builtin_constant_p(recsize))
 371                 return __kfifo_in_generic(fifo, from, n, recsize);
 372         return __kfifo_in_rec(fifo, from, n, recsize);
 373 }
 374
 375 /*
 376  * __kfifo_out_... internal functions for get date from the fifo
 377  * do not call it directly, use kfifo_out_rec() instead
 378  */
 379 extern unsigned int __kfifo_out_n(struct kfifo *fifo,
 380         void *to, unsigned int reclen, unsigned int recsize);
 381
 382 extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
 383         void *to, unsigned int n,
 384         unsigned int recsize, unsigned int *total);
 385
 386 static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
 387         void *to, unsigned int n, unsigned int recsize,
 388         unsigned int *total)
 389 {
 390         unsigned int l;
 391
 392         if (!recsize) {
 393                 l = n;
 394                 if (total)
 395                         *total = l;
 396         } else {
 397                 l = __kfifo_peek_n(fifo, recsize);
 398                 if (total)
 399                         *total = l;
 400                 if (n < l)
 401                         return l;
 402         }
 403
 404         return __kfifo_out_n(fifo, to, l, recsize);
 405 }
 406
 407 /**
 408  * kfifo_out_rec - gets some record data from the FIFO
 409  * @fifo: the fifo to be used.
 410  * @to: where the data must be copied.
 411  * @n: the size of the destination buffer.
 412  * @recsize: size of record field
 413  * @total: pointer where the total number of to copied bytes should stored
 414  *
 415  * This function copies at most @n bytes from the FIFO to @to and returns the
 416  * number of bytes which cannot be copied.
 417  * A returned value greater than the @n value means that the record doesn't
 418  * fit into the @to buffer.
 419  *
 420  * Note that with only one concurrent reader and one concurrent
 421  * writer, you don't need extra locking to use these functions.
 422  */
 423 static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
 424         void *to, unsigned int n, unsigned int recsize,
 425         unsigned int *total)
 426
 427 {
 428         if (!__builtin_constant_p(recsize))
 429                 return __kfifo_out_generic(fifo, to, n, recsize, total);
 430         return __kfifo_out_rec(fifo, to, n, recsize, total);
 431 }
 432
 433 /*
 434  * __kfifo_from_user_... internal functions for transfer from user space into
 435  * the fifo. do not call it directly, use kfifo_from_user_rec() instead
 436  */
 437 extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 438         const void __user *from, unsigned int n, unsigned int recsize);
 439
 440 extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 441         const void __user *from, unsigned int n, unsigned int recsize);
 442
 443 static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
 444         const void __user *from, unsigned int n, unsigned int recsize)
 445 {
 446         unsigned int ret;
 447
 448         ret = __kfifo_from_user_n(fifo, from, n, recsize);
 449
 450         if (likely(ret == 0)) {
 451                 if (recsize)
 452                         __kfifo_poke_n(fifo, recsize, n);
 453                 __kfifo_add_in(fifo, n + recsize);
 454         }
 455         return ret;
 456 }
 457
 458 /**
 459  * kfifo_from_user_rec - puts some data from user space into the FIFO
 460  * @fifo: the fifo to be used.
 461  * @from: pointer to the data to be added.
 462  * @n: the length of the data to be added.
 463  * @recsize: size of record field
 464  *
 465  * This function copies @n bytes from the @from into the
 466  * FIFO and returns the number of bytes which cannot be copied.
 467  *
 468  * If the returned value is equal or less the @n value, the copy_from_user()
 469  * functions has failed. Otherwise the record doesn't fit into the buffer.
 470  *
 471  * Note that with only one concurrent reader and one concurrent
 472  * writer, you don't need extra locking to use these functions.
 473  */
 474 static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
 475         const void __user *from, unsigned int n, unsigned int recsize)
 476 {
 477         if (!__builtin_constant_p(recsize))
 478                 return __kfifo_from_user_generic(fifo, from, n, recsize);
 479         return __kfifo_from_user_rec(fifo, from, n, recsize);
 480 }
 481
 482 /*
 483  * __kfifo_to_user_... internal functions for transfer fifo data into user space
 484  * do not call it directly, use kfifo_to_user_rec() instead
 485  */
 486 extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 487         void __user *to, unsigned int n, unsigned int reclen,
 488         unsigned int recsize);
 489
 490 extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 491         void __user *to, unsigned int n, unsigned int recsize,
 492         unsigned int *total);
 493
 494 static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
 495         void __user *to, unsigned int n,
 496         unsigned int recsize, unsigned int *total)
 497 {
 498         unsigned int l;
 499
 500         if (!recsize) {
 501                 l = n;
 502                 if (total)
 503                         *total = l;
 504         } else {
 505                 l = __kfifo_peek_n(fifo, recsize);
 506                 if (total)
 507                         *total = l;
 508                 if (n < l)
 509                         return l;
 510         }
 511
 512         return __kfifo_to_user_n(fifo, to, n, l, recsize);
 513 }
 514
 515 /**
 516  * kfifo_to_user_rec - gets data from the FIFO and write it to user space
 517  * @fifo: the fifo to be used.
 518  * @to: where the data must be copied.
 519  * @n: the size of the destination buffer.
 520  * @recsize: size of record field
 521  * @total: pointer where the total number of to copied bytes should stored
 522  *
 523  * This function copies at most @n bytes from the FIFO to the @to.
 524  * In case of an error, the function returns the number of bytes which cannot
 525  * be copied.
 526  * If the returned value is equal or less the @n value, the copy_to_user()
 527  * functions has failed. Otherwise the record doesn't fit into the @to buffer.
 528  *
 529  * Note that with only one concurrent reader and one concurrent
 530  * writer, you don't need extra locking to use these functions.
 531  */
 532 static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
 533                 void __user *to, unsigned int n, unsigned int recsize,
 534                 unsigned int *total)
 535 {
 536         if (!__builtin_constant_p(recsize))
 537                 return __kfifo_to_user_generic(fifo, to, n, recsize, total);
 538         return __kfifo_to_user_rec(fifo, to, n, recsize, total);
 539 }
 540
 541 /*
 542  * __kfifo_peek_... internal functions for peek into the next fifo record
 543  * do not call it directly, use kfifo_peek_rec() instead
 544  */
 545 extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
 546                                 unsigned int recsize);
 547
 548 /**
 549  * kfifo_peek_rec - gets the size of the next FIFO record data
 550  * @fifo: the fifo to be used.
 551  * @recsize: size of record field
 552  *
 553  * This function returns the size of the next FIFO record in number of bytes
 554  */
 555 static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
 556         unsigned int recsize)
 557 {
 558         if (!__builtin_constant_p(recsize))
 559                 return __kfifo_peek_generic(fifo, recsize);
 560         if (!recsize)
 561                 return kfifo_len(fifo);
 562         return __kfifo_peek_n(fifo, recsize);
 563 }
 564
 565 /*
 566  * __kfifo_skip_... internal functions for skip the next fifo record
 567  * do not call it directly, use kfifo_skip_rec() instead
 568  */
 569 extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);
 570
 571 static inline void __kfifo_skip_rec(struct kfifo *fifo,
 572         unsigned int recsize)
 573 {
 574         unsigned int l;
 575
 576         if (recsize) {
 577                 l = __kfifo_peek_n(fifo, recsize);
 578
 579                 if (l + recsize <= kfifo_len(fifo)) {
 580                         __kfifo_add_out(fifo, l + recsize);
 581                         return;
 582                 }
 583         }
 584         kfifo_reset_out(fifo);
 585 }
 586
 587 /**
 588  * kfifo_skip_rec - skip the next fifo out record
 589  * @fifo: the fifo to be used.
 590  * @recsize: size of record field
 591  *
 592  * This function skips the next FIFO record
 593  */
 594 static inline void kfifo_skip_rec(struct kfifo *fifo,
 595         unsigned int recsize)
 596 {
 597         if (!__builtin_constant_p(recsize))
 598                 __kfifo_skip_generic(fifo, recsize);
 599         else
 600                 __kfifo_skip_rec(fifo, recsize);
 601 }
 602
 603 /**
 604  * kfifo_avail_rec - returns the number of bytes available in a record FIFO
 605  * @fifo: the fifo to be used.
 606  * @recsize: size of record field
 607  */
 608 static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
 609         unsigned int recsize)
 610 {
 611         unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);
 612
 613         return (l > recsize) ? l - recsize : 0;
 614 }
 615
 616 #endif