kernel/kfifo.c

   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 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/slab.h>
  26 #include <linux/err.h>
  27 #include <linux/kfifo.h>
  28 #include <linux/log2.h>
  29 #include <linux/uaccess.h>
  30
  31 static void _kfifo_init(struct kfifo *fifo, void *buffer,
  32                 unsigned int size)
  33 {
  34         fifo->buffer = buffer;
  35         fifo->size = size;
  36
  37         kfifo_reset(fifo);
  38 }
  39
  40 /**
  41  * kfifo_init - initialize a FIFO using a preallocated buffer
  42  * @fifo: the fifo to assign the buffer
  43  * @buffer: the preallocated buffer to be used.
  44  * @size: the size of the internal buffer, this have to be a power of 2.
  45  *
  46  */
  47 void kfifo_init(struct kfifo *fifo, void *buffer, unsigned int size)
  48 {
  49         /* size must be a power of 2 */
  50         BUG_ON(!is_power_of_2(size));
  51
  52         _kfifo_init(fifo, buffer, size);
  53 }
  54 EXPORT_SYMBOL(kfifo_init);
  55
  56 /**
  57  * kfifo_alloc - allocates a new FIFO internal buffer
  58  * @fifo: the fifo to assign then new buffer
  59  * @size: the size of the buffer to be allocated, this have to be a power of 2.
  60  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  61  *
  62  * This function dynamically allocates a new fifo internal buffer
  63  *
  64  * The size will be rounded-up to a power of 2.
  65  * The buffer will be release with kfifo_free().
  66  * Return 0 if no error, otherwise the an error code
  67  */
  68 int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
  69 {
  70         unsigned char *buffer;
  71
  72         /*
  73          * round up to the next power of 2, since our 'let the indices
  74          * wrap' technique works only in this case.
  75          */
  76         if (!is_power_of_2(size)) {
  77                 BUG_ON(size > 0x80000000);
  78                 size = roundup_pow_of_two(size);
  79         }
  80
  81         buffer = kmalloc(size, gfp_mask);
  82         if (!buffer) {
  83                 _kfifo_init(fifo, 0, 0);
  84                 return -ENOMEM;
  85         }
  86
  87         _kfifo_init(fifo, buffer, size);
  88
  89         return 0;
  90 }
  91 EXPORT_SYMBOL(kfifo_alloc);
  92
  93 /**
  94  * kfifo_free - frees the FIFO internal buffer
  95  * @fifo: the fifo to be freed.
  96  */
  97 void kfifo_free(struct kfifo *fifo)
  98 {
  99         kfree(fifo->buffer);
 100 }
 101 EXPORT_SYMBOL(kfifo_free);
 102
 103 /**
 104  * kfifo_skip - skip output data
 105  * @fifo: the fifo to be used.
 106  * @len: number of bytes to skip
 107  */
 108 void kfifo_skip(struct kfifo *fifo, unsigned int len)
 109 {
 110         if (len < kfifo_len(fifo)) {
 111                 __kfifo_add_out(fifo, len);
 112                 return;
 113         }
 114         kfifo_reset_out(fifo);
 115 }
 116 EXPORT_SYMBOL(kfifo_skip);
 117
 118 static inline void __kfifo_in_data(struct kfifo *fifo,
 119                 const void *from, unsigned int len, unsigned int off)
 120 {
 121         unsigned int l;
 122
 123         /*
 124          * Ensure that we sample the fifo->out index -before- we
 125          * start putting bytes into the kfifo.
 126          */
 127
 128         smp_mb();
 129
 130         off = __kfifo_off(fifo, fifo->in + off);
 131
 132         /* first put the data starting from fifo->in to buffer end */
 133         l = min(len, fifo->size - off);
 134         memcpy(fifo->buffer + off, from, l);
 135
 136         /* then put the rest (if any) at the beginning of the buffer */
 137         memcpy(fifo->buffer, from + l, len - l);
 138 }
 139
 140 static inline void __kfifo_out_data(struct kfifo *fifo,
 141                 void *to, unsigned int len, unsigned int off)
 142 {
 143         unsigned int l;
 144
 145         /*
 146          * Ensure that we sample the fifo->in index -before- we
 147          * start removing bytes from the kfifo.
 148          */
 149
 150         smp_rmb();
 151
 152         off = __kfifo_off(fifo, fifo->out + off);
 153
 154         /* first get the data from fifo->out until the end of the buffer */
 155         l = min(len, fifo->size - off);
 156         memcpy(to, fifo->buffer + off, l);
 157
 158         /* then get the rest (if any) from the beginning of the buffer */
 159         memcpy(to + l, fifo->buffer, len - l);
 160 }
 161
 162 static inline unsigned int __kfifo_from_user_data(struct kfifo *fifo,
 163          const void __user *from, unsigned int len, unsigned int off)
 164 {
 165         unsigned int l;
 166         int ret;
 167
 168         /*
 169          * Ensure that we sample the fifo->out index -before- we
 170          * start putting bytes into the kfifo.
 171          */
 172
 173         smp_mb();
 174
 175         off = __kfifo_off(fifo, fifo->in + off);
 176
 177         /* first put the data starting from fifo->in to buffer end */
 178         l = min(len, fifo->size - off);
 179         ret = copy_from_user(fifo->buffer + off, from, l);
 180
 181         if (unlikely(ret))
 182                 return ret + len - l;
 183
 184         /* then put the rest (if any) at the beginning of the buffer */
 185         return copy_from_user(fifo->buffer, from + l, len - l);
 186 }
 187
 188 static inline unsigned int __kfifo_to_user_data(struct kfifo *fifo,
 189                 void __user *to, unsigned int len, unsigned int off)
 190 {
 191         unsigned int l;
 192         int ret;
 193
 194         /*
 195          * Ensure that we sample the fifo->in index -before- we
 196          * start removing bytes from the kfifo.
 197          */
 198
 199         smp_rmb();
 200
 201         off = __kfifo_off(fifo, fifo->out + off);
 202
 203         /* first get the data from fifo->out until the end of the buffer */
 204         l = min(len, fifo->size - off);
 205         ret = copy_to_user(to, fifo->buffer + off, l);
 206
 207         if (unlikely(ret))
 208                 return ret + len - l;
 209
 210         /* then get the rest (if any) from the beginning of the buffer */
 211         return copy_to_user(to + l, fifo->buffer, len - l);
 212 }
 213
 214 unsigned int __kfifo_in_n(struct kfifo *fifo,
 215         const void *from, unsigned int len, unsigned int recsize)
 216 {
 217         if (kfifo_avail(fifo) < len + recsize)
 218                 return len + 1;
 219
 220         __kfifo_in_data(fifo, from, len, recsize);
 221         return 0;
 222 }
 223 EXPORT_SYMBOL(__kfifo_in_n);
 224
 225 /**
 226  * kfifo_in - puts some data into the FIFO
 227  * @fifo: the fifo to be used.
 228  * @from: the data to be added.
 229  * @len: the length of the data to be added.
 230  *
 231  * This function copies at most @len bytes from the @from buffer into
 232  * the FIFO depending on the free space, and returns the number of
 233  * bytes copied.
 234  *
 235  * Note that with only one concurrent reader and one concurrent
 236  * writer, you don't need extra locking to use these functions.
 237  */
 238 unsigned int kfifo_in(struct kfifo *fifo, const void *from,
 239                                 unsigned int len)
 240 {
 241         len = min(kfifo_avail(fifo), len);
 242
 243         __kfifo_in_data(fifo, from, len, 0);
 244         __kfifo_add_in(fifo, len);
 245         return len;
 246 }
 247 EXPORT_SYMBOL(kfifo_in);
 248
 249 unsigned int __kfifo_in_generic(struct kfifo *fifo,
 250         const void *from, unsigned int len, unsigned int recsize)
 251 {
 252         return __kfifo_in_rec(fifo, from, len, recsize);
 253 }
 254 EXPORT_SYMBOL(__kfifo_in_generic);
 255
 256 unsigned int __kfifo_out_n(struct kfifo *fifo,
 257         void *to, unsigned int len, unsigned int recsize)
 258 {
 259         if (kfifo_len(fifo) < len + recsize)
 260                 return len;
 261
 262         __kfifo_out_data(fifo, to, len, recsize);
 263         __kfifo_add_out(fifo, len + recsize);
 264         return 0;
 265 }
 266 EXPORT_SYMBOL(__kfifo_out_n);
 267
 268 /**
 269  * kfifo_out - gets some data from the FIFO
 270  * @fifo: the fifo to be used.
 271  * @to: where the data must be copied.
 272  * @len: the size of the destination buffer.
 273  *
 274  * This function copies at most @len bytes from the FIFO into the
 275  * @to buffer and returns the number of copied bytes.
 276  *
 277  * Note that with only one concurrent reader and one concurrent
 278  * writer, you don't need extra locking to use these functions.
 279  */
 280 unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
 281 {
 282         len = min(kfifo_len(fifo), len);
 283
 284         __kfifo_out_data(fifo, to, len, 0);
 285         __kfifo_add_out(fifo, len);
 286
 287         return len;
 288 }
 289 EXPORT_SYMBOL(kfifo_out);
 290
 291 unsigned int __kfifo_out_generic(struct kfifo *fifo,
 292         void *to, unsigned int len, unsigned int recsize,
 293         unsigned int *total)
 294 {
 295         return __kfifo_out_rec(fifo, to, len, recsize, total);
 296 }
 297 EXPORT_SYMBOL(__kfifo_out_generic);
 298
 299 unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 300         const void __user *from, unsigned int len, unsigned int recsize)
 301 {
 302         if (kfifo_avail(fifo) < len + recsize)
 303                 return len + 1;
 304
 305         return __kfifo_from_user_data(fifo, from, len, recsize);
 306 }
 307 EXPORT_SYMBOL(__kfifo_from_user_n);
 308
 309 /**
 310  * kfifo_from_user - puts some data from user space into the FIFO
 311  * @fifo: the fifo to be used.
 312  * @from: pointer to the data to be added.
 313  * @len: the length of the data to be added.
 314  *
 315  * This function copies at most @len bytes from the @from into the
 316  * FIFO depending and returns the number of copied bytes.
 317  *
 318  * Note that with only one concurrent reader and one concurrent
 319  * writer, you don't need extra locking to use these functions.
 320  */
 321 unsigned int kfifo_from_user(struct kfifo *fifo,
 322         const void __user *from, unsigned int len)
 323 {
 324         len = min(kfifo_avail(fifo), len);
 325         len -= __kfifo_from_user_data(fifo, from, len, 0);
 326         __kfifo_add_in(fifo, len);
 327         return len;
 328 }
 329 EXPORT_SYMBOL(kfifo_from_user);
 330
 331 unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 332         const void __user *from, unsigned int len, unsigned int recsize)
 333 {
 334         return __kfifo_from_user_rec(fifo, from, len, recsize);
 335 }
 336 EXPORT_SYMBOL(__kfifo_from_user_generic);
 337
 338 unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 339         void __user *to, unsigned int len, unsigned int reclen,
 340         unsigned int recsize)
 341 {
 342         unsigned int ret;
 343
 344         if (kfifo_len(fifo) < reclen + recsize)
 345                 return len;
 346
 347         ret = __kfifo_to_user_data(fifo, to, reclen, recsize);
 348
 349         if (likely(ret == 0))
 350                 __kfifo_add_out(fifo, reclen + recsize);
 351
 352         return ret;
 353 }
 354 EXPORT_SYMBOL(__kfifo_to_user_n);
 355
 356 /**
 357  * kfifo_to_user - gets data from the FIFO and write it to user space
 358  * @fifo: the fifo to be used.
 359  * @to: where the data must be copied.
 360  * @len: the size of the destination buffer.
 361  *
 362  * This function copies at most @len bytes from the FIFO into the
 363  * @to buffer and returns the number of copied bytes.
 364  *
 365  * Note that with only one concurrent reader and one concurrent
 366  * writer, you don't need extra locking to use these functions.
 367  */
 368 unsigned int kfifo_to_user(struct kfifo *fifo,
 369         void __user *to, unsigned int len)
 370 {
 371         len = min(kfifo_len(fifo), len);
 372         len -= __kfifo_to_user_data(fifo, to, len, 0);
 373         __kfifo_add_out(fifo, len);
 374         return len;
 375 }
 376 EXPORT_SYMBOL(kfifo_to_user);
 377
 378 unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 379         void __user *to, unsigned int len, unsigned int recsize,
 380         unsigned int *total)
 381 {
 382         return __kfifo_to_user_rec(fifo, to, len, recsize, total);
 383 }
 384 EXPORT_SYMBOL(__kfifo_to_user_generic);
 385
 386 unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
 387 {
 388         if (recsize == 0)
 389                 return kfifo_avail(fifo);
 390
 391         return __kfifo_peek_n(fifo, recsize);
 392 }
 393 EXPORT_SYMBOL(__kfifo_peek_generic);
 394
 395 void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
 396 {
 397         __kfifo_skip_rec(fifo, recsize);
 398 }
 399 EXPORT_SYMBOL(__kfifo_skip_generic);
 400