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 extern void kfifo_init(struct kfifo *fifo, void *buffer,
 106                         unsigned int size);
 107 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
 108                         gfp_t gfp_mask);
 109 extern void kfifo_free(struct kfifo *fifo);
 110 extern unsigned int kfifo_in(struct kfifo *fifo,
 111                                 const void *from, unsigned int len);
 112 extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
 113                                 void *to, unsigned int len);
 114 extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
 115                                 void *to, unsigned int len, unsigned offset);
 116
 117 /**
 118  * kfifo_initialized - Check if kfifo is initialized.
 119  * @fifo: fifo to check
 120  * Return %true if FIFO is initialized, otherwise %false.
 121  * Assumes the fifo was 0 before.
 122  */
 123 static inline bool kfifo_initialized(struct kfifo *fifo)
 124 {
 125         return fifo->buffer != NULL;
 126 }
 127
 128 /**
 129  * kfifo_reset - removes the entire FIFO contents
 130  * @fifo: the fifo to be emptied.
 131  */
 132 static inline void kfifo_reset(struct kfifo *fifo)
 133 {
 134         fifo->in = fifo->out = 0;
 135 }
 136
 137 /**
 138  * kfifo_reset_out - skip FIFO contents
 139  * @fifo: the fifo to be emptied.
 140  */
 141 static inline void kfifo_reset_out(struct kfifo *fifo)
 142 {
 143         smp_mb();
 144         fifo->out = fifo->in;
 145 }
 146
 147 /**
 148  * kfifo_size - returns the size of the fifo in bytes
 149  * @fifo: the fifo to be used.
 150  */
 151 static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
 152 {
 153         return fifo->size;
 154 }
 155
 156 /**
 157  * kfifo_len - returns the number of used bytes in the FIFO
 158  * @fifo: the fifo to be used.
 159  */
 160 static inline unsigned int kfifo_len(struct kfifo *fifo)
 161 {
 162         register unsigned int   out;
 163
 164         out = fifo->out;
 165         smp_rmb();
 166         return fifo->in - out;
 167 }
 168
 169 /**
 170  * kfifo_is_empty - returns true if the fifo is empty
 171  * @fifo: the fifo to be used.
 172  */
 173 static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
 174 {
 175         return fifo->in == fifo->out;
 176 }
 177
 178 /**
 179  * kfifo_is_full - returns true if the fifo is full
 180  * @fifo: the fifo to be used.
 181  */
 182 static inline __must_check int kfifo_is_full(struct kfifo *fifo)
 183 {
 184         return kfifo_len(fifo) == kfifo_size(fifo);
 185 }
 186
 187 /**
 188  * kfifo_avail - returns the number of bytes available in the FIFO
 189  * @fifo: the fifo to be used.
 190  */
 191 static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
 192 {
 193         return kfifo_size(fifo) - kfifo_len(fifo);
 194 }
 195
 196 /**
 197  * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
 198  * @fifo: the fifo to be used.
 199  * @from: the data to be added.
 200  * @n: the length of the data to be added.
 201  * @lock: pointer to the spinlock to use for locking.
 202  *
 203  * This function copies at most @len bytes from the @from buffer into
 204  * the FIFO depending on the free space, and returns the number of
 205  * bytes copied.
 206  */
 207 static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
 208                 const void *from, unsigned int n, spinlock_t *lock)
 209 {
 210         unsigned long flags;
 211         unsigned int ret;
 212
 213         spin_lock_irqsave(lock, flags);
 214
 215         ret = kfifo_in(fifo, from, n);
 216
 217         spin_unlock_irqrestore(lock, flags);
 218
 219         return ret;
 220 }
 221
 222 /**
 223  * kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
 224  * @fifo: the fifo to be used.
 225  * @to: where the data must be copied.
 226  * @n: the size of the destination buffer.
 227  * @lock: pointer to the spinlock to use for locking.
 228  *
 229  * This function copies at most @len bytes from the FIFO into the
 230  * @to buffer and returns the number of copied bytes.
 231  */
 232 static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 233         void *to, unsigned int n, spinlock_t *lock)
 234 {
 235         unsigned long flags;
 236         unsigned int ret;
 237
 238         spin_lock_irqsave(lock, flags);
 239
 240         ret = kfifo_out(fifo, to, n);
 241
 242         spin_unlock_irqrestore(lock, flags);
 243
 244         return ret;
 245 }
 246
 247 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
 248
 249 extern __must_check int kfifo_from_user(struct kfifo *fifo,
 250         const void __user *from, unsigned int n, unsigned *lenout);
 251
 252 extern __must_check int kfifo_to_user(struct kfifo *fifo,
 253         void __user *to, unsigned int n, unsigned *lenout);
 254
 255 /*
 256  * __kfifo_add_out internal helper function for updating the out offset
 257  */
 258 static inline void __kfifo_add_out(struct kfifo *fifo,
 259                                 unsigned int off)
 260 {
 261         smp_mb();
 262         fifo->out += off;
 263 }
 264
 265 /*
 266  * __kfifo_add_in internal helper function for updating the in offset
 267  */
 268 static inline void __kfifo_add_in(struct kfifo *fifo,
 269                                 unsigned int off)
 270 {
 271         smp_wmb();
 272         fifo->in += off;
 273 }
 274
 275 /*
 276  * __kfifo_off internal helper function for calculating the index of a
 277  * given offeset
 278  */
 279 static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
 280 {
 281         return off & (fifo->size - 1);
 282 }
 283
 284 /*
 285  * __kfifo_peek_n internal helper function for determinate the length of
 286  * the next record in the fifo
 287  */
 288 static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
 289                                 unsigned int recsize)
 290 {
 291 #define __KFIFO_GET(fifo, off, shift) \
 292         ((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))
 293
 294         unsigned int l;
 295
 296         l = __KFIFO_GET(fifo, 0, 0);
 297
 298         if (--recsize)
 299                 l |= __KFIFO_GET(fifo, 1, 8);
 300
 301         return l;
 302 #undef  __KFIFO_GET
 303 }
 304
 305 /*
 306  * __kfifo_poke_n internal helper function for storing the length of
 307  * the next record into the fifo
 308  */
 309 static inline void __kfifo_poke_n(struct kfifo *fifo,
 310                         unsigned int recsize, unsigned int n)
 311 {
 312 #define __KFIFO_PUT(fifo, off, val, shift) \
 313                 ( \
 314                 (fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
 315                 (unsigned char)((val) >> (shift)) \
 316                 )
 317
 318         __KFIFO_PUT(fifo, 0, n, 0);
 319
 320         if (--recsize)
 321                 __KFIFO_PUT(fifo, 1, n, 8);
 322 #undef  __KFIFO_PUT
 323 }
 324
 325 /*
 326  * __kfifo_in_... internal functions for put date into the fifo
 327  * do not call it directly, use kfifo_in_rec() instead
 328  */
 329 extern unsigned int __kfifo_in_n(struct kfifo *fifo,
 330         const void *from, unsigned int n, unsigned int recsize);
 331
 332 extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
 333         const void *from, unsigned int n, unsigned int recsize);
 334
 335 static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
 336         const void *from, unsigned int n, unsigned int recsize)
 337 {
 338         unsigned int ret;
 339
 340         ret = __kfifo_in_n(fifo, from, n, recsize);
 341
 342         if (likely(ret == 0)) {
 343                 if (recsize)
 344                         __kfifo_poke_n(fifo, recsize, n);
 345                 __kfifo_add_in(fifo, n + recsize);
 346         }
 347         return ret;
 348 }
 349
 350 /**
 351  * kfifo_in_rec - puts some record data into the FIFO
 352  * @fifo: the fifo to be used.
 353  * @from: the data to be added.
 354  * @n: the length of the data to be added.
 355  * @recsize: size of record field
 356  *
 357  * This function copies @n bytes from the @from into the FIFO and returns
 358  * the number of bytes which cannot be copied.
 359  * A returned value greater than the @n value means that the record doesn't
 360  * fit into the buffer.
 361  *
 362  * Note that with only one concurrent reader and one concurrent
 363  * writer, you don't need extra locking to use these functions.
 364  */
 365 static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
 366         void *from, unsigned int n, unsigned int recsize)
 367 {
 368         if (!__builtin_constant_p(recsize))
 369                 return __kfifo_in_generic(fifo, from, n, recsize);
 370         return __kfifo_in_rec(fifo, from, n, recsize);
 371 }
 372
 373 /*
 374  * __kfifo_out_... internal functions for get date from the fifo
 375  * do not call it directly, use kfifo_out_rec() instead
 376  */
 377 extern unsigned int __kfifo_out_n(struct kfifo *fifo,
 378         void *to, unsigned int reclen, unsigned int recsize);
 379
 380 extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
 381         void *to, unsigned int n,
 382         unsigned int recsize, unsigned int *total);
 383
 384 static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
 385         void *to, unsigned int n, unsigned int recsize,
 386         unsigned int *total)
 387 {
 388         unsigned int l;
 389
 390         if (!recsize) {
 391                 l = n;
 392                 if (total)
 393                         *total = l;
 394         } else {
 395                 l = __kfifo_peek_n(fifo, recsize);
 396                 if (total)
 397                         *total = l;
 398                 if (n < l)
 399                         return l;
 400         }
 401
 402         return __kfifo_out_n(fifo, to, l, recsize);
 403 }
 404
 405 /**
 406  * kfifo_out_rec - gets some record data from the FIFO
 407  * @fifo: the fifo to be used.
 408  * @to: where the data must be copied.
 409  * @n: the size of the destination buffer.
 410  * @recsize: size of record field
 411  * @total: pointer where the total number of to copied bytes should stored
 412  *
 413  * This function copies at most @n bytes from the FIFO to @to and returns the
 414  * number of bytes which cannot be copied.
 415  * A returned value greater than the @n value means that the record doesn't
 416  * fit into the @to buffer.
 417  *
 418  * Note that with only one concurrent reader and one concurrent
 419  * writer, you don't need extra locking to use these functions.
 420  */
 421 static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
 422         void *to, unsigned int n, unsigned int recsize,
 423         unsigned int *total)
 424
 425 {
 426         if (!__builtin_constant_p(recsize))
 427                 return __kfifo_out_generic(fifo, to, n, recsize, total);
 428         return __kfifo_out_rec(fifo, to, n, recsize, total);
 429 }
 430
 431 /*
 432  * __kfifo_from_user_... internal functions for transfer from user space into
 433  * the fifo. do not call it directly, use kfifo_from_user_rec() instead
 434  */
 435 extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 436         const void __user *from, unsigned int n, unsigned int recsize);
 437
 438 extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 439         const void __user *from, unsigned int n, unsigned int recsize);
 440
 441 static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
 442         const void __user *from, unsigned int n, unsigned int recsize)
 443 {
 444         unsigned int ret;
 445
 446         ret = __kfifo_from_user_n(fifo, from, n, recsize);
 447
 448         if (likely(ret == 0)) {
 449                 if (recsize)
 450                         __kfifo_poke_n(fifo, recsize, n);
 451                 __kfifo_add_in(fifo, n + recsize);
 452         }
 453         return ret;
 454 }
 455
 456 /**
 457  * kfifo_from_user_rec - puts some data from user space into the FIFO
 458  * @fifo: the fifo to be used.
 459  * @from: pointer to the data to be added.
 460  * @n: the length of the data to be added.
 461  * @recsize: size of record field
 462  *
 463  * This function copies @n bytes from the @from into the
 464  * FIFO and returns the number of bytes which cannot be copied.
 465  *
 466  * If the returned value is equal or less the @n value, the copy_from_user()
 467  * functions has failed. Otherwise the record doesn't fit into the buffer.
 468  *
 469  * Note that with only one concurrent reader and one concurrent
 470  * writer, you don't need extra locking to use these functions.
 471  */
 472 static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
 473         const void __user *from, unsigned int n, unsigned int recsize)
 474 {
 475         if (!__builtin_constant_p(recsize))
 476                 return __kfifo_from_user_generic(fifo, from, n, recsize);
 477         return __kfifo_from_user_rec(fifo, from, n, recsize);
 478 }
 479
 480 /*
 481  * __kfifo_to_user_... internal functions for transfer fifo data into user space
 482  * do not call it directly, use kfifo_to_user_rec() instead
 483  */
 484 extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 485         void __user *to, unsigned int n, unsigned int reclen,
 486         unsigned int recsize);
 487
 488 extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 489         void __user *to, unsigned int n, unsigned int recsize,
 490         unsigned int *total);
 491
 492 static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
 493         void __user *to, unsigned int n,
 494         unsigned int recsize, unsigned int *total)
 495 {
 496         unsigned int l;
 497
 498         if (!recsize) {
 499                 l = n;
 500                 if (total)
 501                         *total = l;
 502         } else {
 503                 l = __kfifo_peek_n(fifo, recsize);
 504                 if (total)
 505                         *total = l;
 506                 if (n < l)
 507                         return l;
 508         }
 509
 510         return __kfifo_to_user_n(fifo, to, n, l, recsize);
 511 }
 512
 513 /**
 514  * kfifo_to_user_rec - gets data from the FIFO and write it to user space
 515  * @fifo: the fifo to be used.
 516  * @to: where the data must be copied.
 517  * @n: the size of the destination buffer.
 518  * @recsize: size of record field
 519  * @total: pointer where the total number of to copied bytes should stored
 520  *
 521  * This function copies at most @n bytes from the FIFO to the @to.
 522  * In case of an error, the function returns the number of bytes which cannot
 523  * be copied.
 524  * If the returned value is equal or less the @n value, the copy_to_user()
 525  * functions has failed. Otherwise the record doesn't fit into the @to buffer.
 526  *
 527  * Note that with only one concurrent reader and one concurrent
 528  * writer, you don't need extra locking to use these functions.
 529  */
 530 static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
 531                 void __user *to, unsigned int n, unsigned int recsize,
 532                 unsigned int *total)
 533 {
 534         if (!__builtin_constant_p(recsize))
 535                 return __kfifo_to_user_generic(fifo, to, n, recsize, total);
 536         return __kfifo_to_user_rec(fifo, to, n, recsize, total);
 537 }
 538
 539 /*
 540  * __kfifo_peek_... internal functions for peek into the next fifo record
 541  * do not call it directly, use kfifo_peek_rec() instead
 542  */
 543 extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
 544                                 unsigned int recsize);
 545
 546 /**
 547  * kfifo_peek_rec - gets the size of the next FIFO record data
 548  * @fifo: the fifo to be used.
 549  * @recsize: size of record field
 550  *
 551  * This function returns the size of the next FIFO record in number of bytes
 552  */
 553 static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
 554         unsigned int recsize)
 555 {
 556         if (!__builtin_constant_p(recsize))
 557                 return __kfifo_peek_generic(fifo, recsize);
 558         if (!recsize)
 559                 return kfifo_len(fifo);
 560         return __kfifo_peek_n(fifo, recsize);
 561 }
 562
 563 /*
 564  * __kfifo_skip_... internal functions for skip the next fifo record
 565  * do not call it directly, use kfifo_skip_rec() instead
 566  */
 567 extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);
 568
 569 static inline void __kfifo_skip_rec(struct kfifo *fifo,
 570         unsigned int recsize)
 571 {
 572         unsigned int l;
 573
 574         if (recsize) {
 575                 l = __kfifo_peek_n(fifo, recsize);
 576
 577                 if (l + recsize <= kfifo_len(fifo)) {
 578                         __kfifo_add_out(fifo, l + recsize);
 579                         return;
 580                 }
 581         }
 582         kfifo_reset_out(fifo);
 583 }
 584
 585 /**
 586  * kfifo_skip_rec - skip the next fifo out record
 587  * @fifo: the fifo to be used.
 588  * @recsize: size of record field
 589  *
 590  * This function skips the next FIFO record
 591  */
 592 static inline void kfifo_skip_rec(struct kfifo *fifo,
 593         unsigned int recsize)
 594 {
 595         if (!__builtin_constant_p(recsize))
 596                 __kfifo_skip_generic(fifo, recsize);
 597         else
 598                 __kfifo_skip_rec(fifo, recsize);
 599 }
 600
 601 /**
 602  * kfifo_avail_rec - returns the number of bytes available in a record FIFO
 603  * @fifo: the fifo to be used.
 604  * @recsize: size of record field
 605  */
 606 static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
 607         unsigned int recsize)
 608 {
 609         unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);
 610
 611         return (l > recsize) ? l - recsize : 0;
 612 }
 613
 614 #endif