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 DECLARED_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, unsigned char *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 unsigned char *from, unsigned int len);
 114 extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
 115                                 unsigned char *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 unsigned char *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         unsigned char *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         /*
 232          * optimization: if the FIFO is empty, set the indices to 0
 233          * so we don't wrap the next time
 234          */
 235         if (kfifo_is_empty(fifo))
 236                 kfifo_reset(fifo);
 237
 238         spin_unlock_irqrestore(lock, flags);
 239
 240         return ret;
 241 }
 242
 243 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
 244
 245 extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo,
 246         const void __user *from, unsigned int n);
 247
 248 extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo,
 249         void __user *to, unsigned int n);
 250
 251 /*
 252  * __kfifo_add_out internal helper function for updating the out offset
 253  */
 254 static inline void __kfifo_add_out(struct kfifo *fifo,
 255                                 unsigned int off)
 256 {
 257         smp_mb();
 258         fifo->out += off;
 259 }
 260
 261 /*
 262  * __kfifo_add_in internal helper function for updating the in offset
 263  */
 264 static inline void __kfifo_add_in(struct kfifo *fifo,
 265                                 unsigned int off)
 266 {
 267         smp_wmb();
 268         fifo->in += off;
 269 }
 270
 271 /*
 272  * __kfifo_off internal helper function for calculating the index of a
 273  * given offeset
 274  */
 275 static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
 276 {
 277         return off & (fifo->size - 1);
 278 }
 279
 280 /*
 281  * __kfifo_peek_n internal helper function for determinate the length of
 282  * the next record in the fifo
 283  */
 284 static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
 285                                 unsigned int recsize)
 286 {
 287 #define __KFIFO_GET(fifo, off, shift) \
 288         ((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))
 289
 290         unsigned int l;
 291
 292         l = __KFIFO_GET(fifo, 0, 0);
 293
 294         if (--recsize)
 295                 l |= __KFIFO_GET(fifo, 1, 8);
 296
 297         return l;
 298 #undef  __KFIFO_GET
 299 }
 300
 301 /*
 302  * __kfifo_poke_n internal helper function for storing the length of
 303  * the next record into the fifo
 304  */
 305 static inline void __kfifo_poke_n(struct kfifo *fifo,
 306                         unsigned int recsize, unsigned int n)
 307 {
 308 #define __KFIFO_PUT(fifo, off, val, shift) \
 309                 ( \
 310                 (fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
 311                 (unsigned char)((val) >> (shift)) \
 312                 )
 313
 314         __KFIFO_PUT(fifo, 0, n, 0);
 315
 316         if (--recsize)
 317                 __KFIFO_PUT(fifo, 1, n, 8);
 318 #undef  __KFIFO_PUT
 319 }
 320
 321 /*
 322  * __kfifo_in_... internal functions for put date into the fifo
 323  * do not call it directly, use kfifo_in_rec() instead
 324  */
 325 extern unsigned int __kfifo_in_n(struct kfifo *fifo,
 326         const void *from, unsigned int n, unsigned int recsize);
 327
 328 extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
 329         const void *from, unsigned int n, unsigned int recsize);
 330
 331 static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
 332         const void *from, unsigned int n, unsigned int recsize)
 333 {
 334         unsigned int ret;
 335
 336         ret = __kfifo_in_n(fifo, from, n, recsize);
 337
 338         if (likely(ret == 0)) {
 339                 if (recsize)
 340                         __kfifo_poke_n(fifo, recsize, n);
 341                 __kfifo_add_in(fifo, n + recsize);
 342         }
 343         return ret;
 344 }
 345
 346 /**
 347  * kfifo_in_rec - puts some record data into the FIFO
 348  * @fifo: the fifo to be used.
 349  * @from: the data to be added.
 350  * @n: the length of the data to be added.
 351  * @recsize: size of record field
 352  *
 353  * This function copies @n bytes from the @from into the FIFO and returns
 354  * the number of bytes which cannot be copied.
 355  * A returned value greater than the @n value means that the record doesn't
 356  * fit into the buffer.
 357  *
 358  * Note that with only one concurrent reader and one concurrent
 359  * writer, you don't need extra locking to use these functions.
 360  */
 361 static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
 362         void *from, unsigned int n, unsigned int recsize)
 363 {
 364         if (!__builtin_constant_p(recsize))
 365                 return __kfifo_in_generic(fifo, from, n, recsize);
 366         return __kfifo_in_rec(fifo, from, n, recsize);
 367 }
 368
 369 /*
 370  * __kfifo_out_... internal functions for get date from the fifo
 371  * do not call it directly, use kfifo_out_rec() instead
 372  */
 373 extern unsigned int __kfifo_out_n(struct kfifo *fifo,
 374         void *to, unsigned int reclen, unsigned int recsize);
 375
 376 extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
 377         void *to, unsigned int n,
 378         unsigned int recsize, unsigned int *total);
 379
 380 static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
 381         void *to, unsigned int n, unsigned int recsize,
 382         unsigned int *total)
 383 {
 384         unsigned int l;
 385
 386         if (!recsize) {
 387                 l = n;
 388                 if (total)
 389                         *total = l;
 390         } else {
 391                 l = __kfifo_peek_n(fifo, recsize);
 392                 if (total)
 393                         *total = l;
 394                 if (n < l)
 395                         return l;
 396         }
 397
 398         return __kfifo_out_n(fifo, to, l, recsize);
 399 }
 400
 401 /**
 402  * kfifo_out_rec - gets some record data from the FIFO
 403  * @fifo: the fifo to be used.
 404  * @to: where the data must be copied.
 405  * @n: the size of the destination buffer.
 406  * @recsize: size of record field
 407  * @total: pointer where the total number of to copied bytes should stored
 408  *
 409  * This function copies at most @n bytes from the FIFO to @to and returns the
 410  * number of bytes which cannot be copied.
 411  * A returned value greater than the @n value means that the record doesn't
 412  * fit into the @to buffer.
 413  *
 414  * Note that with only one concurrent reader and one concurrent
 415  * writer, you don't need extra locking to use these functions.
 416  */
 417 static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
 418         void *to, unsigned int n, unsigned int recsize,
 419         unsigned int *total)
 420
 421 {
 422         if (!__builtin_constant_p(recsize))
 423                 return __kfifo_out_generic(fifo, to, n, recsize, total);
 424         return __kfifo_out_rec(fifo, to, n, recsize, total);
 425 }
 426
 427 /*
 428  * __kfifo_from_user_... internal functions for transfer from user space into
 429  * the fifo. do not call it directly, use kfifo_from_user_rec() instead
 430  */
 431 extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 432         const void __user *from, unsigned int n, unsigned int recsize);
 433
 434 extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 435         const void __user *from, unsigned int n, unsigned int recsize);
 436
 437 static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
 438         const void __user *from, unsigned int n, unsigned int recsize)
 439 {
 440         unsigned int ret;
 441
 442         ret = __kfifo_from_user_n(fifo, from, n, recsize);
 443
 444         if (likely(ret == 0)) {
 445                 if (recsize)
 446                         __kfifo_poke_n(fifo, recsize, n);
 447                 __kfifo_add_in(fifo, n + recsize);
 448         }
 449         return ret;
 450 }
 451
 452 /**
 453  * kfifo_from_user_rec - puts some data from user space into the FIFO
 454  * @fifo: the fifo to be used.
 455  * @from: pointer to the data to be added.
 456  * @n: the length of the data to be added.
 457  * @recsize: size of record field
 458  *
 459  * This function copies @n bytes from the @from into the
 460  * FIFO and returns the number of bytes which cannot be copied.
 461  *
 462  * If the returned value is equal or less the @n value, the copy_from_user()
 463  * functions has failed. Otherwise the record doesn't fit into the buffer.
 464  *
 465  * Note that with only one concurrent reader and one concurrent
 466  * writer, you don't need extra locking to use these functions.
 467  */
 468 static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
 469         const void __user *from, unsigned int n, unsigned int recsize)
 470 {
 471         if (!__builtin_constant_p(recsize))
 472                 return __kfifo_from_user_generic(fifo, from, n, recsize);
 473         return __kfifo_from_user_rec(fifo, from, n, recsize);
 474 }
 475
 476 /*
 477  * __kfifo_to_user_... internal functions for transfer fifo data into user space
 478  * do not call it directly, use kfifo_to_user_rec() instead
 479  */
 480 extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 481         void __user *to, unsigned int n, unsigned int reclen,
 482         unsigned int recsize);
 483
 484 extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 485         void __user *to, unsigned int n, unsigned int recsize,
 486         unsigned int *total);
 487
 488 static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
 489         void __user *to, unsigned int n,
 490         unsigned int recsize, unsigned int *total)
 491 {
 492         unsigned int l;
 493
 494         if (!recsize) {
 495                 l = n;
 496                 if (total)
 497                         *total = l;
 498         } else {
 499                 l = __kfifo_peek_n(fifo, recsize);
 500                 if (total)
 501                         *total = l;
 502                 if (n < l)
 503                         return l;
 504         }
 505
 506         return __kfifo_to_user_n(fifo, to, n, l, recsize);
 507 }
 508
 509 /**
 510  * kfifo_to_user_rec - gets data from the FIFO and write it to user space
 511  * @fifo: the fifo to be used.
 512  * @to: where the data must be copied.
 513  * @n: the size of the destination buffer.
 514  * @recsize: size of record field
 515  * @total: pointer where the total number of to copied bytes should stored
 516  *
 517  * This function copies at most @n bytes from the FIFO to the @to.
 518  * In case of an error, the function returns the number of bytes which cannot
 519  * be copied.
 520  * If the returned value is equal or less the @n value, the copy_to_user()
 521  * functions has failed. Otherwise the record doesn't fit into the @to buffer.
 522  *
 523  * Note that with only one concurrent reader and one concurrent
 524  * writer, you don't need extra locking to use these functions.
 525  */
 526 static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
 527                 void __user *to, unsigned int n, unsigned int recsize,
 528                 unsigned int *total)
 529 {
 530         if (!__builtin_constant_p(recsize))
 531                 return __kfifo_to_user_generic(fifo, to, n, recsize, total);
 532         return __kfifo_to_user_rec(fifo, to, n, recsize, total);
 533 }
 534
 535 /*
 536  * __kfifo_peek_... internal functions for peek into the next fifo record
 537  * do not call it directly, use kfifo_peek_rec() instead
 538  */
 539 extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
 540                                 unsigned int recsize);
 541
 542 /**
 543  * kfifo_peek_rec - gets the size of the next FIFO record data
 544  * @fifo: the fifo to be used.
 545  * @recsize: size of record field
 546  *
 547  * This function returns the size of the next FIFO record in number of bytes
 548  */
 549 static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
 550         unsigned int recsize)
 551 {
 552         if (!__builtin_constant_p(recsize))
 553                 return __kfifo_peek_generic(fifo, recsize);
 554         if (!recsize)
 555                 return kfifo_len(fifo);
 556         return __kfifo_peek_n(fifo, recsize);
 557 }
 558
 559 /*
 560  * __kfifo_skip_... internal functions for skip the next fifo record
 561  * do not call it directly, use kfifo_skip_rec() instead
 562  */
 563 extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);
 564
 565 static inline void __kfifo_skip_rec(struct kfifo *fifo,
 566         unsigned int recsize)
 567 {
 568         unsigned int l;
 569
 570         if (recsize) {
 571                 l = __kfifo_peek_n(fifo, recsize);
 572
 573                 if (l + recsize <= kfifo_len(fifo)) {
 574                         __kfifo_add_out(fifo, l + recsize);
 575                         return;
 576                 }
 577         }
 578         kfifo_reset_out(fifo);
 579 }
 580
 581 /**
 582  * kfifo_skip_rec - skip the next fifo out record
 583  * @fifo: the fifo to be used.
 584  * @recsize: size of record field
 585  *
 586  * This function skips the next FIFO record
 587  */
 588 static inline void kfifo_skip_rec(struct kfifo *fifo,
 589         unsigned int recsize)
 590 {
 591         if (!__builtin_constant_p(recsize))
 592                 __kfifo_skip_generic(fifo, recsize);
 593         else
 594                 __kfifo_skip_rec(fifo, recsize);
 595 }
 596
 597 /**
 598  * kfifo_avail_rec - returns the number of bytes available in a record FIFO
 599  * @fifo: the fifo to be used.
 600  * @recsize: size of record field
 601  */
 602 static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
 603         unsigned int recsize)
 604 {
 605         unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);
 606
 607         return (l > recsize) ? l - recsize : 0;
 608 }
 609
 610 #endif