linux/kernel/kfifo.c
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   1/*
   2 * A generic kernel FIFO implementation
   3 *
   4 * Copyright (C) 2009/2010 Stefani Seibold <stefani@seibold.net>
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License as published by
   8 * the Free Software Foundation; either version 2 of the License, or
   9 * (at your option) any later version.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, write to the Free Software
  18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 *
  20 */
  21
  22#include <linux/kernel.h>
  23#include <linux/module.h>
  24#include <linux/slab.h>
  25#include <linux/err.h>
  26#include <linux/log2.h>
  27#include <linux/uaccess.h>
  28#include <linux/kfifo.h>
  29
  30/*
  31 * internal helper to calculate the unused elements in a fifo
  32 */
  33static inline unsigned int kfifo_unused(struct __kfifo *fifo)
  34{
  35        return (fifo->mask + 1) - (fifo->in - fifo->out);
  36}
  37
  38int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
  39                size_t esize, gfp_t gfp_mask)
  40{
  41        /*
  42         * round down to the next power of 2, since our 'let the indices
  43         * wrap' technique works only in this case.
  44         */
  45        if (!is_power_of_2(size))
  46                size = rounddown_pow_of_two(size);
  47
  48        fifo->in = 0;
  49        fifo->out = 0;
  50        fifo->esize = esize;
  51
  52        if (size < 2) {
  53                fifo->data = NULL;
  54                fifo->mask = 0;
  55                return -EINVAL;
  56        }
  57
  58        fifo->data = kmalloc(size * esize, gfp_mask);
  59
  60        if (!fifo->data) {
  61                fifo->mask = 0;
  62                return -ENOMEM;
  63        }
  64        fifo->mask = size - 1;
  65
  66        return 0;
  67}
  68EXPORT_SYMBOL(__kfifo_alloc);
  69
  70void __kfifo_free(struct __kfifo *fifo)
  71{
  72        kfree(fifo->data);
  73        fifo->in = 0;
  74        fifo->out = 0;
  75        fifo->esize = 0;
  76        fifo->data = NULL;
  77        fifo->mask = 0;
  78}
  79EXPORT_SYMBOL(__kfifo_free);
  80
  81int __kfifo_init(struct __kfifo *fifo, void *buffer,
  82                unsigned int size, size_t esize)
  83{
  84        size /= esize;
  85
  86        if (!is_power_of_2(size))
  87                size = rounddown_pow_of_two(size);
  88
  89        fifo->in = 0;
  90        fifo->out = 0;
  91        fifo->esize = esize;
  92        fifo->data = buffer;
  93
  94        if (size < 2) {
  95                fifo->mask = 0;
  96                return -EINVAL;
  97        }
  98        fifo->mask = size - 1;
  99
 100        return 0;
 101}
 102EXPORT_SYMBOL(__kfifo_init);
 103
 104static void kfifo_copy_in(struct __kfifo *fifo, const void *src,
 105                unsigned int len, unsigned int off)
 106{
 107        unsigned int size = fifo->mask + 1;
 108        unsigned int esize = fifo->esize;
 109        unsigned int l;
 110
 111        off &= fifo->mask;
 112        if (esize != 1) {
 113                off *= esize;
 114                size *= esize;
 115                len *= esize;
 116        }
 117        l = min(len, size - off);
 118
 119        memcpy(fifo->data + off, src, l);
 120        memcpy(fifo->data, src + l, len - l);
 121        /*
 122         * make sure that the data in the fifo is up to date before
 123         * incrementing the fifo->in index counter
 124         */
 125        smp_wmb();
 126}
 127
 128unsigned int __kfifo_in(struct __kfifo *fifo,
 129                const void *buf, unsigned int len)
 130{
 131        unsigned int l;
 132
 133        l = kfifo_unused(fifo);
 134        if (len > l)
 135                len = l;
 136
 137        kfifo_copy_in(fifo, buf, len, fifo->in);
 138        fifo->in += len;
 139        return len;
 140}
 141EXPORT_SYMBOL(__kfifo_in);
 142
 143static void kfifo_copy_out(struct __kfifo *fifo, void *dst,
 144                unsigned int len, unsigned int off)
 145{
 146        unsigned int size = fifo->mask + 1;
 147        unsigned int esize = fifo->esize;
 148        unsigned int l;
 149
 150        off &= fifo->mask;
 151        if (esize != 1) {
 152                off *= esize;
 153                size *= esize;
 154                len *= esize;
 155        }
 156        l = min(len, size - off);
 157
 158        memcpy(dst, fifo->data + off, l);
 159        memcpy(dst + l, fifo->data, len - l);
 160        /*
 161         * make sure that the data is copied before
 162         * incrementing the fifo->out index counter
 163         */
 164        smp_wmb();
 165}
 166
 167unsigned int __kfifo_out_peek(struct __kfifo *fifo,
 168                void *buf, unsigned int len)
 169{
 170        unsigned int l;
 171
 172        l = fifo->in - fifo->out;
 173        if (len > l)
 174                len = l;
 175
 176        kfifo_copy_out(fifo, buf, len, fifo->out);
 177        return len;
 178}
 179EXPORT_SYMBOL(__kfifo_out_peek);
 180
 181unsigned int __kfifo_out(struct __kfifo *fifo,
 182                void *buf, unsigned int len)
 183{
 184        len = __kfifo_out_peek(fifo, buf, len);
 185        fifo->out += len;
 186        return len;
 187}
 188EXPORT_SYMBOL(__kfifo_out);
 189
 190static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,
 191        const void __user *from, unsigned int len, unsigned int off,
 192        unsigned int *copied)
 193{
 194        unsigned int size = fifo->mask + 1;
 195        unsigned int esize = fifo->esize;
 196        unsigned int l;
 197        unsigned long ret;
 198
 199        off &= fifo->mask;
 200        if (esize != 1) {
 201                off *= esize;
 202                size *= esize;
 203                len *= esize;
 204        }
 205        l = min(len, size - off);
 206
 207        ret = copy_from_user(fifo->data + off, from, l);
 208        if (unlikely(ret))
 209                ret = DIV_ROUND_UP(ret + len - l, esize);
 210        else {
 211                ret = copy_from_user(fifo->data, from + l, len - l);
 212                if (unlikely(ret))
 213                        ret = DIV_ROUND_UP(ret, esize);
 214        }
 215        /*
 216         * make sure that the data in the fifo is up to date before
 217         * incrementing the fifo->in index counter
 218         */
 219        smp_wmb();
 220        *copied = len - ret;
 221        /* return the number of elements which are not copied */
 222        return ret;
 223}
 224
 225int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,
 226                unsigned long len, unsigned int *copied)
 227{
 228        unsigned int l;
 229        unsigned long ret;
 230        unsigned int esize = fifo->esize;
 231        int err;
 232
 233        if (esize != 1)
 234                len /= esize;
 235
 236        l = kfifo_unused(fifo);
 237        if (len > l)
 238                len = l;
 239
 240        ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);
 241        if (unlikely(ret)) {
 242                len -= ret;
 243                err = -EFAULT;
 244        } else
 245                err = 0;
 246        fifo->in += len;
 247        return err;
 248}
 249EXPORT_SYMBOL(__kfifo_from_user);
 250
 251static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void __user *to,
 252                unsigned int len, unsigned int off, unsigned int *copied)
 253{
 254        unsigned int l;
 255        unsigned long ret;
 256        unsigned int size = fifo->mask + 1;
 257        unsigned int esize = fifo->esize;
 258
 259        off &= fifo->mask;
 260        if (esize != 1) {
 261                off *= esize;
 262                size *= esize;
 263                len *= esize;
 264        }
 265        l = min(len, size - off);
 266
 267        ret = copy_to_user(to, fifo->data + off, l);
 268        if (unlikely(ret))
 269                ret = DIV_ROUND_UP(ret + len - l, esize);
 270        else {
 271                ret = copy_to_user(to + l, fifo->data, len - l);
 272                if (unlikely(ret))
 273                        ret = DIV_ROUND_UP(ret, esize);
 274        }
 275        /*
 276         * make sure that the data is copied before
 277         * incrementing the fifo->out index counter
 278         */
 279        smp_wmb();
 280        *copied = len - ret;
 281        /* return the number of elements which are not copied */
 282        return ret;
 283}
 284
 285int __kfifo_to_user(struct __kfifo *fifo, void __user *to,
 286                unsigned long len, unsigned int *copied)
 287{
 288        unsigned int l;
 289        unsigned long ret;
 290        unsigned int esize = fifo->esize;
 291        int err;
 292
 293        if (esize != 1)
 294                len /= esize;
 295
 296        l = fifo->in - fifo->out;
 297        if (len > l)
 298                len = l;
 299        ret = kfifo_copy_to_user(fifo, to, len, fifo->out, copied);
 300        if (unlikely(ret)) {
 301                len -= ret;
 302                err = -EFAULT;
 303        } else
 304                err = 0;
 305        fifo->out += len;
 306        return err;
 307}
 308EXPORT_SYMBOL(__kfifo_to_user);
 309
 310static int setup_sgl_buf(struct scatterlist *sgl, void *buf,
 311                int nents, unsigned int len)
 312{
 313        int n;
 314        unsigned int l;
 315        unsigned int off;
 316        struct page *page;
 317
 318        if (!nents)
 319                return 0;
 320
 321        if (!len)
 322                return 0;
 323
 324        n = 0;
 325        page = virt_to_page(buf);
 326        off = offset_in_page(buf);
 327        l = 0;
 328
 329        while (len >= l + PAGE_SIZE - off) {
 330                struct page *npage;
 331
 332                l += PAGE_SIZE;
 333                buf += PAGE_SIZE;
 334                npage = virt_to_page(buf);
 335                if (page_to_phys(page) != page_to_phys(npage) - l) {
 336                        sg_set_page(sgl, page, l - off, off);
 337                        sgl = sg_next(sgl);
 338                        if (++n == nents || sgl == NULL)
 339                                return n;
 340                        page = npage;
 341                        len -= l - off;
 342                        l = off = 0;
 343                }
 344        }
 345        sg_set_page(sgl, page, len, off);
 346        return n + 1;
 347}
 348
 349static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
 350                int nents, unsigned int len, unsigned int off)
 351{
 352        unsigned int size = fifo->mask + 1;
 353        unsigned int esize = fifo->esize;
 354        unsigned int l;
 355        unsigned int n;
 356
 357        off &= fifo->mask;
 358        if (esize != 1) {
 359                off *= esize;
 360                size *= esize;
 361                len *= esize;
 362        }
 363        l = min(len, size - off);
 364
 365        n = setup_sgl_buf(sgl, fifo->data + off, nents, l);
 366        n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l);
 367
 368        return n;
 369}
 370
 371unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,
 372                struct scatterlist *sgl, int nents, unsigned int len)
 373{
 374        unsigned int l;
 375
 376        l = kfifo_unused(fifo);
 377        if (len > l)
 378                len = l;
 379
 380        return setup_sgl(fifo, sgl, nents, len, fifo->in);
 381}
 382EXPORT_SYMBOL(__kfifo_dma_in_prepare);
 383
 384unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,
 385                struct scatterlist *sgl, int nents, unsigned int len)
 386{
 387        unsigned int l;
 388
 389        l = fifo->in - fifo->out;
 390        if (len > l)
 391                len = l;
 392
 393        return setup_sgl(fifo, sgl, nents, len, fifo->out);
 394}
 395EXPORT_SYMBOL(__kfifo_dma_out_prepare);
 396
 397unsigned int __kfifo_max_r(unsigned int len, size_t recsize)
 398{
 399        unsigned int max = (1 << (recsize << 3)) - 1;
 400
 401        if (len > max)
 402                return max;
 403        return len;
 404}
 405
 406#define __KFIFO_PEEK(data, out, mask) \
 407        ((data)[(out) & (mask)])
 408/*
 409 * __kfifo_peek_n internal helper function for determinate the length of
 410 * the next record in the fifo
 411 */
 412static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)
 413{
 414        unsigned int l;
 415        unsigned int mask = fifo->mask;
 416        unsigned char *data = fifo->data;
 417
 418        l = __KFIFO_PEEK(data, fifo->out, mask);
 419
 420        if (--recsize)
 421                l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;
 422
 423        return l;
 424}
 425
 426#define __KFIFO_POKE(data, in, mask, val) \
 427        ( \
 428        (data)[(in) & (mask)] = (unsigned char)(val) \
 429        )
 430
 431/*
 432 * __kfifo_poke_n internal helper function for storeing the length of
 433 * the record into the fifo
 434 */
 435static void __kfifo_poke_n(struct __kfifo *fifo, unsigned int n, size_t recsize)
 436{
 437        unsigned int mask = fifo->mask;
 438        unsigned char *data = fifo->data;
 439
 440        __KFIFO_POKE(data, fifo->in, mask, n);
 441
 442        if (recsize > 1)
 443                __KFIFO_POKE(data, fifo->in + 1, mask, n >> 8);
 444}
 445
 446unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize)
 447{
 448        return __kfifo_peek_n(fifo, recsize);
 449}
 450EXPORT_SYMBOL(__kfifo_len_r);
 451
 452unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf,
 453                unsigned int len, size_t recsize)
 454{
 455        if (len + recsize > kfifo_unused(fifo))
 456                return 0;
 457
 458        __kfifo_poke_n(fifo, len, recsize);
 459
 460        kfifo_copy_in(fifo, buf, len, fifo->in + recsize);
 461        fifo->in += len + recsize;
 462        return len;
 463}
 464EXPORT_SYMBOL(__kfifo_in_r);
 465
 466static unsigned int kfifo_out_copy_r(struct __kfifo *fifo,
 467        void *buf, unsigned int len, size_t recsize, unsigned int *n)
 468{
 469        *n = __kfifo_peek_n(fifo, recsize);
 470
 471        if (len > *n)
 472                len = *n;
 473
 474        kfifo_copy_out(fifo, buf, len, fifo->out + recsize);
 475        return len;
 476}
 477
 478unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf,
 479                unsigned int len, size_t recsize)
 480{
 481        unsigned int n;
 482
 483        if (fifo->in == fifo->out)
 484                return 0;
 485
 486        return kfifo_out_copy_r(fifo, buf, len, recsize, &n);
 487}
 488EXPORT_SYMBOL(__kfifo_out_peek_r);
 489
 490unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf,
 491                unsigned int len, size_t recsize)
 492{
 493        unsigned int n;
 494
 495        if (fifo->in == fifo->out)
 496                return 0;
 497
 498        len = kfifo_out_copy_r(fifo, buf, len, recsize, &n);
 499        fifo->out += n + recsize;
 500        return len;
 501}
 502EXPORT_SYMBOL(__kfifo_out_r);
 503
 504void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize)
 505{
 506        unsigned int n;
 507
 508        n = __kfifo_peek_n(fifo, recsize);
 509        fifo->out += n + recsize;
 510}
 511EXPORT_SYMBOL(__kfifo_skip_r);
 512
 513int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from,
 514        unsigned long len, unsigned int *copied, size_t recsize)
 515{
 516        unsigned long ret;
 517
 518        len = __kfifo_max_r(len, recsize);
 519
 520        if (len + recsize > kfifo_unused(fifo)) {
 521                *copied = 0;
 522                return 0;
 523        }
 524
 525        __kfifo_poke_n(fifo, len, recsize);
 526
 527        ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied);
 528        if (unlikely(ret)) {
 529                *copied = 0;
 530                return -EFAULT;
 531        }
 532        fifo->in += len + recsize;
 533        return 0;
 534}
 535EXPORT_SYMBOL(__kfifo_from_user_r);
 536
 537int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,
 538        unsigned long len, unsigned int *copied, size_t recsize)
 539{
 540        unsigned long ret;
 541        unsigned int n;
 542
 543        if (fifo->in == fifo->out) {
 544                *copied = 0;
 545                return 0;
 546        }
 547
 548        n = __kfifo_peek_n(fifo, recsize);
 549        if (len > n)
 550                len = n;
 551
 552        ret = kfifo_copy_to_user(fifo, to, len, fifo->out + recsize, copied);
 553        if (unlikely(ret)) {
 554                *copied = 0;
 555                return -EFAULT;
 556        }
 557        fifo->out += n + recsize;
 558        return 0;
 559}
 560EXPORT_SYMBOL(__kfifo_to_user_r);
 561
 562unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
 563        struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
 564{
 565        if (!nents)
 566                BUG();
 567
 568        len = __kfifo_max_r(len, recsize);
 569
 570        if (len + recsize > kfifo_unused(fifo))
 571                return 0;
 572
 573        return setup_sgl(fifo, sgl, nents, len, fifo->in + recsize);
 574}
 575EXPORT_SYMBOL(__kfifo_dma_in_prepare_r);
 576
 577void __kfifo_dma_in_finish_r(struct __kfifo *fifo,
 578        unsigned int len, size_t recsize)
 579{
 580        len = __kfifo_max_r(len, recsize);
 581        __kfifo_poke_n(fifo, len, recsize);
 582        fifo->in += len + recsize;
 583}
 584EXPORT_SYMBOL(__kfifo_dma_in_finish_r);
 585
 586unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
 587        struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
 588{
 589        if (!nents)
 590                BUG();
 591
 592        len = __kfifo_max_r(len, recsize);
 593
 594        if (len + recsize > fifo->in - fifo->out)
 595                return 0;
 596
 597        return setup_sgl(fifo, sgl, nents, len, fifo->out + recsize);
 598}
 599EXPORT_SYMBOL(__kfifo_dma_out_prepare_r);
 600
 601void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize)
 602{
 603        unsigned int len;
 604
 605        len = __kfifo_peek_n(fifo, recsize);
 606        fifo->out += len + recsize;
 607}
 608EXPORT_SYMBOL(__kfifo_dma_out_finish_r);
 609
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