Commit | Line | Data |
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3e7ee490 HJ |
1 | /* |
2 | * | |
3 | * Copyright (c) 2009, Microsoft Corporation. | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify it | |
6 | * under the terms and conditions of the GNU General Public License, | |
7 | * version 2, as published by the Free Software Foundation. | |
8 | * | |
9 | * This program is distributed in the hope it will be useful, but WITHOUT | |
10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for | |
12 | * more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License along with | |
15 | * this program; if not, write to the Free Software Foundation, Inc., 59 Temple | |
16 | * Place - Suite 330, Boston, MA 02111-1307 USA. | |
17 | * | |
18 | * Authors: | |
19 | * Haiyang Zhang <haiyangz@microsoft.com> | |
20 | * Hank Janssen <hjanssen@microsoft.com> | |
b2a5a585 | 21 | * K. Y. Srinivasan <kys@microsoft.com> |
3e7ee490 HJ |
22 | * |
23 | */ | |
0a46618d | 24 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
3e7ee490 | 25 | |
a0086dc5 GKH |
26 | #include <linux/kernel.h> |
27 | #include <linux/mm.h> | |
645954c5 | 28 | #include "logging.h" |
8f078ca6 | 29 | #include "ring_buffer.h" |
3e7ee490 | 30 | |
3e7ee490 | 31 | |
454f18a9 BP |
32 | /* #defines */ |
33 | ||
34 | ||
35 | /* Amount of space to write to */ | |
0686e4f4 | 36 | #define BYTES_AVAIL_TO_WRITE(r, w, z) ((w) >= (r)) ? ((z) - ((w) - (r))) : ((r) - (w)) |
3e7ee490 HJ |
37 | |
38 | ||
b2a5a585 S |
39 | /* |
40 | * | |
41 | * hv_get_ringbuffer_availbytes() | |
42 | * | |
43 | * Get number of bytes available to read and to write to | |
44 | * for the specified ring buffer | |
45 | */ | |
3e7ee490 | 46 | static inline void |
2b8a912e | 47 | hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi, |
1ac58644 | 48 | u32 *read, u32 *write) |
3e7ee490 | 49 | { |
4408f531 | 50 | u32 read_loc, write_loc; |
3e7ee490 | 51 | |
454f18a9 | 52 | /* Capture the read/write indices before they changed */ |
82f8bd40 HZ |
53 | read_loc = rbi->ring_buffer->read_index; |
54 | write_loc = rbi->ring_buffer->write_index; | |
3e7ee490 | 55 | |
82f8bd40 HZ |
56 | *write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->ring_datasize); |
57 | *read = rbi->ring_datasize - *write; | |
3e7ee490 HJ |
58 | } |
59 | ||
b2a5a585 S |
60 | /* |
61 | * hv_get_next_write_location() | |
62 | * | |
63 | * Get the next write location for the specified ring buffer | |
64 | * | |
65 | */ | |
4d643114 | 66 | static inline u32 |
2b8a912e | 67 | hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 68 | { |
fc8c72eb | 69 | u32 next = ring_info->ring_buffer->write_index; |
3e7ee490 | 70 | |
3e7ee490 HJ |
71 | return next; |
72 | } | |
73 | ||
b2a5a585 S |
74 | /* |
75 | * hv_set_next_write_location() | |
76 | * | |
77 | * Set the next write location for the specified ring buffer | |
78 | * | |
79 | */ | |
3e7ee490 | 80 | static inline void |
2b8a912e | 81 | hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, |
fc8c72eb | 82 | u32 next_write_location) |
3e7ee490 | 83 | { |
fc8c72eb | 84 | ring_info->ring_buffer->write_index = next_write_location; |
3e7ee490 HJ |
85 | } |
86 | ||
b2a5a585 S |
87 | /* |
88 | * hv_get_next_read_location() | |
89 | * | |
90 | * Get the next read location for the specified ring buffer | |
91 | */ | |
4d643114 | 92 | static inline u32 |
2b8a912e | 93 | hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 94 | { |
fc8c72eb | 95 | u32 next = ring_info->ring_buffer->read_index; |
3e7ee490 | 96 | |
3e7ee490 HJ |
97 | return next; |
98 | } | |
99 | ||
b2a5a585 S |
100 | /* |
101 | * hv_get_next_readlocation_withoffset() | |
102 | * | |
103 | * Get the next read location + offset for the specified ring buffer. | |
104 | * This allows the caller to skip | |
105 | */ | |
4d643114 | 106 | static inline u32 |
2b8a912e | 107 | hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, |
1ac58644 | 108 | u32 offset) |
3e7ee490 | 109 | { |
fc8c72eb | 110 | u32 next = ring_info->ring_buffer->read_index; |
3e7ee490 | 111 | |
fc8c72eb HZ |
112 | next += offset; |
113 | next %= ring_info->ring_datasize; | |
3e7ee490 HJ |
114 | |
115 | return next; | |
116 | } | |
117 | ||
b2a5a585 S |
118 | /* |
119 | * | |
120 | * hv_set_next_read_location() | |
121 | * | |
122 | * Set the next read location for the specified ring buffer | |
123 | * | |
124 | */ | |
3e7ee490 | 125 | static inline void |
2b8a912e | 126 | hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, |
fc8c72eb | 127 | u32 next_read_location) |
3e7ee490 | 128 | { |
fc8c72eb | 129 | ring_info->ring_buffer->read_index = next_read_location; |
3e7ee490 HJ |
130 | } |
131 | ||
132 | ||
b2a5a585 S |
133 | /* |
134 | * | |
135 | * hv_get_ring_buffer() | |
136 | * | |
137 | * Get the start of the ring buffer | |
138 | */ | |
8282c400 | 139 | static inline void * |
2b8a912e | 140 | hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 141 | { |
fc8c72eb | 142 | return (void *)ring_info->ring_buffer->buffer; |
3e7ee490 HJ |
143 | } |
144 | ||
145 | ||
b2a5a585 S |
146 | /* |
147 | * | |
148 | * hv_get_ring_buffersize() | |
149 | * | |
150 | * Get the size of the ring buffer | |
151 | */ | |
4d643114 | 152 | static inline u32 |
2b8a912e | 153 | hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 154 | { |
fc8c72eb | 155 | return ring_info->ring_datasize; |
3e7ee490 HJ |
156 | } |
157 | ||
b2a5a585 S |
158 | /* |
159 | * | |
160 | * hv_get_ring_bufferindices() | |
161 | * | |
162 | * Get the read and write indices as u64 of the specified ring buffer | |
163 | * | |
164 | */ | |
59471438 | 165 | static inline u64 |
2b8a912e | 166 | hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 167 | { |
fc8c72eb | 168 | return (u64)ring_info->ring_buffer->write_index << 32; |
3e7ee490 HJ |
169 | } |
170 | ||
171 | ||
b2a5a585 S |
172 | /* |
173 | * | |
174 | * hv_dump_ring_info() | |
175 | * | |
176 | * Dump out to console the ring buffer info | |
177 | * | |
178 | */ | |
549bf93f | 179 | void hv_dump_ring_info(struct hv_ring_buffer_info *ring_info, char *prefix) |
3e7ee490 | 180 | { |
fc8c72eb HZ |
181 | u32 bytes_avail_towrite; |
182 | u32 bytes_avail_toread; | |
3e7ee490 | 183 | |
2b8a912e | 184 | hv_get_ringbuffer_availbytes(ring_info, |
fc8c72eb HZ |
185 | &bytes_avail_toread, |
186 | &bytes_avail_towrite); | |
3e7ee490 | 187 | |
4408f531 B |
188 | DPRINT(VMBUS, |
189 | DEBUG_RING_LVL, | |
190 | "%s <<ringinfo %p buffer %p avail write %u " | |
191 | "avail read %u read idx %u write idx %u>>", | |
fc8c72eb HZ |
192 | prefix, |
193 | ring_info, | |
194 | ring_info->ring_buffer->buffer, | |
195 | bytes_avail_towrite, | |
196 | bytes_avail_toread, | |
197 | ring_info->ring_buffer->read_index, | |
198 | ring_info->ring_buffer->write_index); | |
3e7ee490 HJ |
199 | } |
200 | ||
454f18a9 | 201 | |
8f1136ae S |
202 | /* |
203 | * | |
204 | * hv_copyfrom_ringbuffer() | |
205 | * | |
206 | * Helper routine to copy to source from ring buffer. | |
207 | * Assume there is enough room. Handles wrap-around in src case only!! | |
208 | * | |
209 | */ | |
210 | static u32 hv_copyfrom_ringbuffer( | |
211 | struct hv_ring_buffer_info *ring_info, | |
212 | void *dest, | |
213 | u32 destlen, | |
214 | u32 start_read_offset) | |
215 | { | |
216 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
217 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
218 | ||
219 | u32 frag_len; | |
220 | ||
221 | /* wrap-around detected at the src */ | |
222 | if (destlen > ring_buffer_size - start_read_offset) { | |
223 | frag_len = ring_buffer_size - start_read_offset; | |
224 | ||
225 | memcpy(dest, ring_buffer + start_read_offset, frag_len); | |
226 | memcpy(dest + frag_len, ring_buffer, destlen - frag_len); | |
227 | } else | |
228 | ||
229 | memcpy(dest, ring_buffer + start_read_offset, destlen); | |
230 | ||
231 | ||
232 | start_read_offset += destlen; | |
233 | start_read_offset %= ring_buffer_size; | |
234 | ||
235 | return start_read_offset; | |
236 | } | |
237 | ||
238 | ||
454f18a9 | 239 | |
4d643114 | 240 | static u32 |
2b8a912e | 241 | hv_copyto_ringbuffer( |
fc8c72eb HZ |
242 | struct hv_ring_buffer_info *ring_info, |
243 | u32 start_write_offset, | |
244 | void *src, | |
245 | u32 srclen); | |
3e7ee490 | 246 | |
3e7ee490 | 247 | |
b2a5a585 S |
248 | /* |
249 | * | |
250 | * hv_ringbuffer_get_debuginfo() | |
251 | * | |
252 | * Get various debug metrics for the specified ring buffer | |
253 | * | |
254 | */ | |
a75b61d5 | 255 | void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, |
80682b7a | 256 | struct hv_ring_buffer_debug_info *debug_info) |
3e7ee490 | 257 | { |
fc8c72eb HZ |
258 | u32 bytes_avail_towrite; |
259 | u32 bytes_avail_toread; | |
3e7ee490 | 260 | |
fc8c72eb | 261 | if (ring_info->ring_buffer) { |
2b8a912e | 262 | hv_get_ringbuffer_availbytes(ring_info, |
fc8c72eb HZ |
263 | &bytes_avail_toread, |
264 | &bytes_avail_towrite); | |
3e7ee490 | 265 | |
fc8c72eb HZ |
266 | debug_info->bytes_avail_toread = bytes_avail_toread; |
267 | debug_info->bytes_avail_towrite = bytes_avail_towrite; | |
82f8bd40 | 268 | debug_info->current_read_index = |
fc8c72eb | 269 | ring_info->ring_buffer->read_index; |
82f8bd40 | 270 | debug_info->current_write_index = |
fc8c72eb | 271 | ring_info->ring_buffer->write_index; |
82f8bd40 | 272 | debug_info->current_interrupt_mask = |
fc8c72eb | 273 | ring_info->ring_buffer->interrupt_mask; |
3e7ee490 HJ |
274 | } |
275 | } | |
276 | ||
277 | ||
b2a5a585 S |
278 | /* |
279 | * | |
280 | * hv_get_ringbuffer_interrupt_mask() | |
281 | * | |
282 | * Get the interrupt mask for the specified ring buffer | |
283 | * | |
284 | */ | |
decc49da | 285 | u32 hv_get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *rbi) |
3e7ee490 | 286 | { |
82f8bd40 | 287 | return rbi->ring_buffer->interrupt_mask; |
3e7ee490 HJ |
288 | } |
289 | ||
b2a5a585 S |
290 | /* |
291 | * | |
292 | * hv_ringbuffer_init() | |
293 | * | |
294 | *Initialize the ring buffer | |
295 | * | |
296 | */ | |
72a95cbc | 297 | int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, |
fc8c72eb | 298 | void *buffer, u32 buflen) |
3e7ee490 | 299 | { |
4a1b3acc | 300 | if (sizeof(struct hv_ring_buffer) != PAGE_SIZE) |
3324fb40 | 301 | return -EINVAL; |
3e7ee490 | 302 | |
fc8c72eb | 303 | memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); |
3e7ee490 | 304 | |
fc8c72eb HZ |
305 | ring_info->ring_buffer = (struct hv_ring_buffer *)buffer; |
306 | ring_info->ring_buffer->read_index = | |
307 | ring_info->ring_buffer->write_index = 0; | |
3e7ee490 | 308 | |
fc8c72eb HZ |
309 | ring_info->ring_size = buflen; |
310 | ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer); | |
3e7ee490 | 311 | |
fc8c72eb | 312 | spin_lock_init(&ring_info->ring_lock); |
3e7ee490 HJ |
313 | |
314 | return 0; | |
315 | } | |
316 | ||
b2a5a585 S |
317 | /* |
318 | * | |
319 | * hv_ringbuffer_cleanup() | |
320 | * | |
321 | * Cleanup the ring buffer | |
322 | * | |
323 | */ | |
2dba688b | 324 | void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 325 | { |
3e7ee490 HJ |
326 | } |
327 | ||
b2a5a585 S |
328 | /* |
329 | * | |
330 | * hv_ringbuffer_write() | |
331 | * | |
332 | * Write to the ring buffer | |
333 | * | |
334 | */ | |
633c4dce | 335 | int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, |
3523a805 | 336 | struct scatterlist *sglist, u32 sgcount) |
3e7ee490 | 337 | { |
4408f531 | 338 | int i = 0; |
fc8c72eb HZ |
339 | u32 bytes_avail_towrite; |
340 | u32 bytes_avail_toread; | |
341 | u32 totalbytes_towrite = 0; | |
3e7ee490 | 342 | |
b219b3f7 | 343 | struct scatterlist *sg; |
fc8c72eb HZ |
344 | volatile u32 next_write_location; |
345 | u64 prev_indices = 0; | |
a98f96ee | 346 | unsigned long flags; |
3e7ee490 | 347 | |
b219b3f7 | 348 | for_each_sg(sglist, sg, sgcount, i) |
3e7ee490 | 349 | { |
fc8c72eb | 350 | totalbytes_towrite += sg->length; |
3e7ee490 HJ |
351 | } |
352 | ||
fc8c72eb | 353 | totalbytes_towrite += sizeof(u64); |
3e7ee490 | 354 | |
fc8c72eb | 355 | spin_lock_irqsave(&outring_info->ring_lock, flags); |
3e7ee490 | 356 | |
2b8a912e | 357 | hv_get_ringbuffer_availbytes(outring_info, |
fc8c72eb HZ |
358 | &bytes_avail_toread, |
359 | &bytes_avail_towrite); | |
3e7ee490 | 360 | |
3e7ee490 | 361 | |
4408f531 B |
362 | /* If there is only room for the packet, assume it is full. */ |
363 | /* Otherwise, the next time around, we think the ring buffer */ | |
454f18a9 | 364 | /* is empty since the read index == write index */ |
fc8c72eb | 365 | if (bytes_avail_towrite <= totalbytes_towrite) { |
fc8c72eb | 366 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); |
3e7ee490 HJ |
367 | return -1; |
368 | } | |
369 | ||
454f18a9 | 370 | /* Write to the ring buffer */ |
2b8a912e | 371 | next_write_location = hv_get_next_write_location(outring_info); |
3e7ee490 | 372 | |
b219b3f7 | 373 | for_each_sg(sglist, sg, sgcount, i) |
3e7ee490 | 374 | { |
2b8a912e | 375 | next_write_location = hv_copyto_ringbuffer(outring_info, |
fc8c72eb | 376 | next_write_location, |
b219b3f7 NP |
377 | sg_virt(sg), |
378 | sg->length); | |
3e7ee490 HJ |
379 | } |
380 | ||
454f18a9 | 381 | /* Set previous packet start */ |
2b8a912e | 382 | prev_indices = hv_get_ring_bufferindices(outring_info); |
3e7ee490 | 383 | |
2b8a912e | 384 | next_write_location = hv_copyto_ringbuffer(outring_info, |
fc8c72eb HZ |
385 | next_write_location, |
386 | &prev_indices, | |
b219b3f7 | 387 | sizeof(u64)); |
3e7ee490 | 388 | |
454f18a9 | 389 | /* Make sure we flush all writes before updating the writeIndex */ |
28b6ca9c | 390 | mb(); |
3e7ee490 | 391 | |
454f18a9 | 392 | /* Now, update the write location */ |
2b8a912e | 393 | hv_set_next_write_location(outring_info, next_write_location); |
3e7ee490 | 394 | |
3e7ee490 | 395 | |
fc8c72eb | 396 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); |
3e7ee490 HJ |
397 | return 0; |
398 | } | |
399 | ||
400 | ||
b2a5a585 S |
401 | /* |
402 | * | |
403 | * hv_ringbuffer_peek() | |
404 | * | |
405 | * Read without advancing the read index | |
406 | * | |
407 | */ | |
a89186c2 | 408 | int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info, |
fc8c72eb | 409 | void *Buffer, u32 buflen) |
3e7ee490 | 410 | { |
fc8c72eb HZ |
411 | u32 bytes_avail_towrite; |
412 | u32 bytes_avail_toread; | |
413 | u32 next_read_location = 0; | |
a98f96ee | 414 | unsigned long flags; |
3e7ee490 | 415 | |
fc8c72eb | 416 | spin_lock_irqsave(&Inring_info->ring_lock, flags); |
3e7ee490 | 417 | |
2b8a912e | 418 | hv_get_ringbuffer_availbytes(Inring_info, |
fc8c72eb HZ |
419 | &bytes_avail_toread, |
420 | &bytes_avail_towrite); | |
3e7ee490 | 421 | |
454f18a9 | 422 | /* Make sure there is something to read */ |
fc8c72eb | 423 | if (bytes_avail_toread < buflen) { |
3e7ee490 | 424 | |
fc8c72eb | 425 | spin_unlock_irqrestore(&Inring_info->ring_lock, flags); |
3e7ee490 HJ |
426 | |
427 | return -1; | |
428 | } | |
429 | ||
454f18a9 | 430 | /* Convert to byte offset */ |
2b8a912e | 431 | next_read_location = hv_get_next_read_location(Inring_info); |
3e7ee490 | 432 | |
2b8a912e | 433 | next_read_location = hv_copyfrom_ringbuffer(Inring_info, |
4408f531 | 434 | Buffer, |
fc8c72eb HZ |
435 | buflen, |
436 | next_read_location); | |
3e7ee490 | 437 | |
fc8c72eb | 438 | spin_unlock_irqrestore(&Inring_info->ring_lock, flags); |
3e7ee490 HJ |
439 | |
440 | return 0; | |
441 | } | |
442 | ||
443 | ||
b2a5a585 S |
444 | /* |
445 | * | |
446 | * hv_ringbuffer_read() | |
447 | * | |
448 | * Read and advance the read index | |
449 | * | |
450 | */ | |
38397c8a | 451 | int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer, |
fc8c72eb | 452 | u32 buflen, u32 offset) |
3e7ee490 | 453 | { |
fc8c72eb HZ |
454 | u32 bytes_avail_towrite; |
455 | u32 bytes_avail_toread; | |
456 | u32 next_read_location = 0; | |
457 | u64 prev_indices = 0; | |
a98f96ee | 458 | unsigned long flags; |
3e7ee490 | 459 | |
fc8c72eb | 460 | if (buflen <= 0) |
a16e1485 | 461 | return -EINVAL; |
3e7ee490 | 462 | |
fc8c72eb | 463 | spin_lock_irqsave(&inring_info->ring_lock, flags); |
3e7ee490 | 464 | |
2b8a912e | 465 | hv_get_ringbuffer_availbytes(inring_info, |
fc8c72eb HZ |
466 | &bytes_avail_toread, |
467 | &bytes_avail_towrite); | |
3e7ee490 | 468 | |
454f18a9 | 469 | /* Make sure there is something to read */ |
fc8c72eb | 470 | if (bytes_avail_toread < buflen) { |
fc8c72eb | 471 | spin_unlock_irqrestore(&inring_info->ring_lock, flags); |
3e7ee490 HJ |
472 | |
473 | return -1; | |
474 | } | |
475 | ||
1ac58644 | 476 | next_read_location = |
2b8a912e | 477 | hv_get_next_readlocation_withoffset(inring_info, offset); |
3e7ee490 | 478 | |
2b8a912e | 479 | next_read_location = hv_copyfrom_ringbuffer(inring_info, |
fc8c72eb HZ |
480 | buffer, |
481 | buflen, | |
482 | next_read_location); | |
3e7ee490 | 483 | |
2b8a912e | 484 | next_read_location = hv_copyfrom_ringbuffer(inring_info, |
fc8c72eb | 485 | &prev_indices, |
4408f531 | 486 | sizeof(u64), |
fc8c72eb | 487 | next_read_location); |
3e7ee490 | 488 | |
454f18a9 | 489 | /* Make sure all reads are done before we update the read index since */ |
4408f531 B |
490 | /* the writer may start writing to the read area once the read index */ |
491 | /*is updated */ | |
28b6ca9c | 492 | mb(); |
3e7ee490 | 493 | |
454f18a9 | 494 | /* Update the read index */ |
2b8a912e | 495 | hv_set_next_read_location(inring_info, next_read_location); |
3e7ee490 | 496 | |
fc8c72eb | 497 | spin_unlock_irqrestore(&inring_info->ring_lock, flags); |
3e7ee490 HJ |
498 | |
499 | return 0; | |
500 | } | |
501 | ||
502 | ||
b2a5a585 S |
503 | /* |
504 | * | |
505 | * hv_copyto_ringbuffer() | |
506 | * | |
507 | * Helper routine to copy from source to ring buffer. | |
508 | * Assume there is enough room. Handles wrap-around in dest case only!! | |
509 | * | |
510 | */ | |
bd1de709 | 511 | static u32 |
2b8a912e | 512 | hv_copyto_ringbuffer( |
fc8c72eb HZ |
513 | struct hv_ring_buffer_info *ring_info, |
514 | u32 start_write_offset, | |
515 | void *src, | |
516 | u32 srclen) | |
3e7ee490 | 517 | { |
2b8a912e S |
518 | void *ring_buffer = hv_get_ring_buffer(ring_info); |
519 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
fc8c72eb | 520 | u32 frag_len; |
3e7ee490 | 521 | |
4408f531 | 522 | /* wrap-around detected! */ |
fc8c72eb | 523 | if (srclen > ring_buffer_size - start_write_offset) { |
fc8c72eb HZ |
524 | frag_len = ring_buffer_size - start_write_offset; |
525 | memcpy(ring_buffer + start_write_offset, src, frag_len); | |
526 | memcpy(ring_buffer, src + frag_len, srclen - frag_len); | |
4408f531 | 527 | } else |
fc8c72eb | 528 | memcpy(ring_buffer + start_write_offset, src, srclen); |
3e7ee490 | 529 | |
fc8c72eb HZ |
530 | start_write_offset += srclen; |
531 | start_write_offset %= ring_buffer_size; | |
3e7ee490 | 532 | |
fc8c72eb | 533 | return start_write_offset; |
3e7ee490 HJ |
534 | } |
535 |