1/* 2 * videobuf2-dma-contig.c - DMA contig memory allocator for videobuf2 3 * 4 * Copyright (C) 2010 Samsung Electronics 5 * 6 * Author: Pawel Osciak <pawel@osciak.com> 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License as published by 10 * the Free Software Foundation. 11 */ 12 13#include <linux/dma-buf.h> 14#include <linux/module.h> 15#include <linux/refcount.h> 16#include <linux/scatterlist.h> 17#include <linux/sched.h> 18#include <linux/slab.h> 19#include <linux/dma-mapping.h> 20 21#include <media/videobuf2-v4l2.h> 22#include <media/videobuf2-dma-contig.h> 23#include <media/videobuf2-memops.h> 24 25struct vb2_dc_buf { 26 struct device *dev; 27 void *vaddr; 28 unsigned long size; 29 void *cookie; 30 dma_addr_t dma_addr; 31 unsigned long attrs; 32 enum dma_data_direction dma_dir; 33 struct sg_table *dma_sgt; 34 struct frame_vector *vec; 35 36 /* MMAP related */ 37 struct vb2_vmarea_handler handler; 38 refcount_t refcount; 39 struct sg_table *sgt_base; 40 41 /* DMABUF related */ 42 struct dma_buf_attachment *db_attach; 43}; 44 45/*********************************************/ 46/* scatterlist table functions */ 47/*********************************************/ 48 49static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt) 50{ 51 struct scatterlist *s; 52 dma_addr_t expected = sg_dma_address(sgt->sgl); 53 unsigned int i; 54 unsigned long size = 0; 55 56 for_each_sgtable_dma_sg(sgt, s, i) { 57 if (sg_dma_address(s) != expected) 58 break; 59 expected += sg_dma_len(s); 60 size += sg_dma_len(s); 61 } 62 return size; 63} 64 65/*********************************************/ 66/* callbacks for all buffers */ 67/*********************************************/ 68 69static void *vb2_dc_cookie(void *buf_priv) 70{ 71 struct vb2_dc_buf *buf = buf_priv; 72 73 return &buf->dma_addr; 74} 75 76static void *vb2_dc_vaddr(void *buf_priv) 77{ 78 struct vb2_dc_buf *buf = buf_priv; 79 80 if (!buf->vaddr && buf->db_attach) 81 buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf); 82 83 return buf->vaddr; 84} 85 86static unsigned int vb2_dc_num_users(void *buf_priv) 87{ 88 struct vb2_dc_buf *buf = buf_priv; 89 90 return refcount_read(&buf->refcount); 91} 92 93static void vb2_dc_prepare(void *buf_priv) 94{ 95 struct vb2_dc_buf *buf = buf_priv; 96 struct sg_table *sgt = buf->dma_sgt; 97 98 if (!sgt) 99 return; 100 101 dma_sync_sgtable_for_device(buf->dev, sgt, buf->dma_dir); 102} 103 104static void vb2_dc_finish(void *buf_priv) 105{ 106 struct vb2_dc_buf *buf = buf_priv; 107 struct sg_table *sgt = buf->dma_sgt; 108 109 if (!sgt) 110 return; 111 112 dma_sync_sgtable_for_cpu(buf->dev, sgt, buf->dma_dir); 113} 114 115/*********************************************/ 116/* callbacks for MMAP buffers */ 117/*********************************************/ 118 119static void vb2_dc_put(void *buf_priv) 120{ 121 struct vb2_dc_buf *buf = buf_priv; 122 123 if (!refcount_dec_and_test(&buf->refcount)) 124 return; 125 126 if (buf->sgt_base) { 127 sg_free_table(buf->sgt_base); 128 kfree(buf->sgt_base); 129 } 130 dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr, 131 buf->attrs); 132 put_device(buf->dev); 133 kfree(buf); 134} 135 136static void *vb2_dc_alloc(struct device *dev, unsigned long attrs, 137 unsigned long size, enum dma_data_direction dma_dir, 138 gfp_t gfp_flags) 139{ 140 struct vb2_dc_buf *buf; 141 142 if (WARN_ON(!dev)) 143 return ERR_PTR(-EINVAL); 144 145 buf = kzalloc(sizeof *buf, GFP_KERNEL); 146 if (!buf) 147 return ERR_PTR(-ENOMEM); 148 149 buf->attrs = attrs; 150 buf->cookie = dma_alloc_attrs(dev, size, &buf->dma_addr, 151 GFP_KERNEL | gfp_flags, buf->attrs); 152 if (!buf->cookie) { 153 dev_err(dev, "dma_alloc_coherent of size %lu failed\n", size); 154 kfree(buf); 155 return ERR_PTR(-ENOMEM); 156 } 157 158 if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0) 159 buf->vaddr = buf->cookie; 160 161 /* Prevent the device from being released while the buffer is used */ 162 buf->dev = get_device(dev); 163 buf->size = size; 164 buf->dma_dir = dma_dir; 165 166 buf->handler.refcount = &buf->refcount; 167 buf->handler.put = vb2_dc_put; 168 buf->handler.arg = buf; 169 170 refcount_set(&buf->refcount, 1); 171 172 return buf; 173} 174 175static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma) 176{ 177 struct vb2_dc_buf *buf = buf_priv; 178 int ret; 179 180 if (!buf) { 181 printk(KERN_ERR "No buffer to map\n"); 182 return -EINVAL; 183 } 184 185 ret = dma_mmap_attrs(buf->dev, vma, buf->cookie, 186 buf->dma_addr, buf->size, buf->attrs); 187 188 if (ret) { 189 pr_err("Remapping memory failed, error: %d\n", ret); 190 return ret; 191 } 192 193 vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP; 194 vma->vm_private_data = &buf->handler; 195 vma->vm_ops = &vb2_common_vm_ops; 196 197 vma->vm_ops->open(vma); 198 199 pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %lu\n", 200 __func__, (unsigned long)buf->dma_addr, vma->vm_start, 201 buf->size); 202 203 return 0; 204} 205 206/*********************************************/ 207/* DMABUF ops for exporters */ 208/*********************************************/ 209 210struct vb2_dc_attachment { 211 struct sg_table sgt; 212 enum dma_data_direction dma_dir; 213}; 214 215static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, 216 struct dma_buf_attachment *dbuf_attach) 217{ 218 struct vb2_dc_attachment *attach; 219 unsigned int i; 220 struct scatterlist *rd, *wr; 221 struct sg_table *sgt; 222 struct vb2_dc_buf *buf = dbuf->priv; 223 int ret; 224 225 attach = kzalloc(sizeof(*attach), GFP_KERNEL); 226 if (!attach) 227 return -ENOMEM; 228 229 sgt = &attach->sgt; 230 /* Copy the buf->base_sgt scatter list to the attachment, as we can't 231 * map the same scatter list to multiple attachments at the same time. 232 */ 233 ret = sg_alloc_table(sgt, buf->sgt_base->orig_nents, GFP_KERNEL); 234 if (ret) { 235 kfree(attach); 236 return -ENOMEM; 237 } 238 239 rd = buf->sgt_base->sgl; 240 wr = sgt->sgl; 241 for (i = 0; i < sgt->orig_nents; ++i) { 242 sg_set_page(wr, sg_page(rd), rd->length, rd->offset); 243 rd = sg_next(rd); 244 wr = sg_next(wr); 245 } 246 247 attach->dma_dir = DMA_NONE; 248 dbuf_attach->priv = attach; 249 250 return 0; 251} 252 253static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf, 254 struct dma_buf_attachment *db_attach) 255{ 256 struct vb2_dc_attachment *attach = db_attach->priv; 257 struct sg_table *sgt; 258 259 if (!attach) 260 return; 261 262 sgt = &attach->sgt; 263 264 /* release the scatterlist cache */ 265 if (attach->dma_dir != DMA_NONE) 266 /* 267 * Cache sync can be skipped here, as the vb2_dc memory is 268 * allocated from device coherent memory, which means the 269 * memory locations do not require any explicit cache 270 * maintenance prior or after being used by the device. 271 */ 272 dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 273 DMA_ATTR_SKIP_CPU_SYNC); 274 sg_free_table(sgt); 275 kfree(attach); 276 db_attach->priv = NULL; 277} 278 279static struct sg_table *vb2_dc_dmabuf_ops_map( 280 struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir) 281{ 282 struct vb2_dc_attachment *attach = db_attach->priv; 283 /* stealing dmabuf mutex to serialize map/unmap operations */ 284 struct mutex *lock = &db_attach->dmabuf->lock; 285 struct sg_table *sgt; 286 287 mutex_lock(lock); 288 289 sgt = &attach->sgt; 290 /* return previously mapped sg table */ 291 if (attach->dma_dir == dma_dir) { 292 mutex_unlock(lock); 293 return sgt; 294 } 295 296 /* release any previous cache */ 297 if (attach->dma_dir != DMA_NONE) { 298 dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 299 DMA_ATTR_SKIP_CPU_SYNC); 300 attach->dma_dir = DMA_NONE; 301 } 302 303 /* 304 * mapping to the client with new direction, no cache sync 305 * required see comment in vb2_dc_dmabuf_ops_detach() 306 */ 307 if (dma_map_sgtable(db_attach->dev, sgt, dma_dir, 308 DMA_ATTR_SKIP_CPU_SYNC)) { 309 pr_err("failed to map scatterlist\n"); 310 mutex_unlock(lock); 311 return ERR_PTR(-EIO); 312 } 313 314 attach->dma_dir = dma_dir; 315 316 mutex_unlock(lock); 317 318 return sgt; 319} 320 321static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach, 322 struct sg_table *sgt, enum dma_data_direction dma_dir) 323{ 324 /* nothing to be done here */ 325} 326 327static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf) 328{ 329 /* drop reference obtained in vb2_dc_get_dmabuf */ 330 vb2_dc_put(dbuf->priv); 331} 332 333static int 334vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf, 335 enum dma_data_direction direction) 336{ 337 return 0; 338} 339 340static int 341vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf, 342 enum dma_data_direction direction) 343{ 344 return 0; 345} 346 347static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf) 348{ 349 struct vb2_dc_buf *buf = dbuf->priv; 350 351 return buf->vaddr; 352} 353 354static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf, 355 struct vm_area_struct *vma) 356{ 357 return vb2_dc_mmap(dbuf->priv, vma); 358} 359 360static const struct dma_buf_ops vb2_dc_dmabuf_ops = { 361 .attach = vb2_dc_dmabuf_ops_attach, 362 .detach = vb2_dc_dmabuf_ops_detach, 363 .map_dma_buf = vb2_dc_dmabuf_ops_map, 364 .unmap_dma_buf = vb2_dc_dmabuf_ops_unmap, 365 .begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access, 366 .end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access, 367 .vmap = vb2_dc_dmabuf_ops_vmap, 368 .mmap = vb2_dc_dmabuf_ops_mmap, 369 .release = vb2_dc_dmabuf_ops_release, 370}; 371 372static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf) 373{ 374 int ret; 375 struct sg_table *sgt; 376 377 sgt = kmalloc(sizeof(*sgt), GFP_KERNEL); 378 if (!sgt) { 379 dev_err(buf->dev, "failed to alloc sg table\n"); 380 return NULL; 381 } 382 383 ret = dma_get_sgtable_attrs(buf->dev, sgt, buf->cookie, buf->dma_addr, 384 buf->size, buf->attrs); 385 if (ret < 0) { 386 dev_err(buf->dev, "failed to get scatterlist from DMA API\n"); 387 kfree(sgt); 388 return NULL; 389 } 390 391 return sgt; 392} 393 394static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags) 395{ 396 struct vb2_dc_buf *buf = buf_priv; 397 struct dma_buf *dbuf; 398 DEFINE_DMA_BUF_EXPORT_INFO(exp_info); 399 400 exp_info.ops = &vb2_dc_dmabuf_ops; 401 exp_info.size = buf->size; 402 exp_info.flags = flags; 403 exp_info.priv = buf; 404 405 if (!buf->sgt_base) 406 buf->sgt_base = vb2_dc_get_base_sgt(buf); 407 408 if (WARN_ON(!buf->sgt_base)) 409 return NULL; 410 411 dbuf = dma_buf_export(&exp_info); 412 if (IS_ERR(dbuf)) 413 return NULL; 414 415 /* dmabuf keeps reference to vb2 buffer */ 416 refcount_inc(&buf->refcount); 417 418 return dbuf; 419} 420 421/*********************************************/ 422/* callbacks for USERPTR buffers */ 423/*********************************************/ 424 425static void vb2_dc_put_userptr(void *buf_priv) 426{ 427 struct vb2_dc_buf *buf = buf_priv; 428 struct sg_table *sgt = buf->dma_sgt; 429 int i; 430 struct page **pages; 431 432 if (sgt) { 433 /* 434 * No need to sync to CPU, it's already synced to the CPU 435 * since the finish() memop will have been called before this. 436 */ 437 dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, 438 DMA_ATTR_SKIP_CPU_SYNC); 439 pages = frame_vector_pages(buf->vec); 440 /* sgt should exist only if vector contains pages... */ 441 BUG_ON(IS_ERR(pages)); 442 if (buf->dma_dir == DMA_FROM_DEVICE || 443 buf->dma_dir == DMA_BIDIRECTIONAL) 444 for (i = 0; i < frame_vector_count(buf->vec); i++) 445 set_page_dirty_lock(pages[i]); 446 sg_free_table(sgt); 447 kfree(sgt); 448 } else { 449 dma_unmap_resource(buf->dev, buf->dma_addr, buf->size, 450 buf->dma_dir, 0); 451 } 452 vb2_destroy_framevec(buf->vec); 453 kfree(buf); 454} 455 456static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr, 457 unsigned long size, enum dma_data_direction dma_dir) 458{ 459 struct vb2_dc_buf *buf; 460 struct frame_vector *vec; 461 unsigned int offset; 462 int n_pages, i; 463 int ret = 0; 464 struct sg_table *sgt; 465 unsigned long contig_size; 466 unsigned long dma_align = dma_get_cache_alignment(); 467 468 /* Only cache aligned DMA transfers are reliable */ 469 if (!IS_ALIGNED(vaddr | size, dma_align)) { 470 pr_debug("user data must be aligned to %lu bytes\n", dma_align); 471 return ERR_PTR(-EINVAL); 472 } 473 474 if (!size) { 475 pr_debug("size is zero\n"); 476 return ERR_PTR(-EINVAL); 477 } 478 479 if (WARN_ON(!dev)) 480 return ERR_PTR(-EINVAL); 481 482 buf = kzalloc(sizeof *buf, GFP_KERNEL); 483 if (!buf) 484 return ERR_PTR(-ENOMEM); 485 486 buf->dev = dev; 487 buf->dma_dir = dma_dir; 488 489 offset = lower_32_bits(offset_in_page(vaddr)); 490 vec = vb2_create_framevec(vaddr, size); 491 if (IS_ERR(vec)) { 492 ret = PTR_ERR(vec); 493 goto fail_buf; 494 } 495 buf->vec = vec; 496 n_pages = frame_vector_count(vec); 497 ret = frame_vector_to_pages(vec); 498 if (ret < 0) { 499 unsigned long *nums = frame_vector_pfns(vec); 500 501 /* 502 * Failed to convert to pages... Check the memory is physically 503 * contiguous and use direct mapping 504 */ 505 for (i = 1; i < n_pages; i++) 506 if (nums[i-1] + 1 != nums[i]) 507 goto fail_pfnvec; 508 buf->dma_addr = dma_map_resource(buf->dev, 509 __pfn_to_phys(nums[0]), size, buf->dma_dir, 0); 510 if (dma_mapping_error(buf->dev, buf->dma_addr)) { 511 ret = -ENOMEM; 512 goto fail_pfnvec; 513 } 514 goto out; 515 } 516 517 sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); 518 if (!sgt) { 519 pr_err("failed to allocate sg table\n"); 520 ret = -ENOMEM; 521 goto fail_pfnvec; 522 } 523 524 ret = sg_alloc_table_from_pages(sgt, frame_vector_pages(vec), n_pages, 525 offset, size, GFP_KERNEL); 526 if (ret) { 527 pr_err("failed to initialize sg table\n"); 528 goto fail_sgt; 529 } 530 531 /* 532 * No need to sync to the device, this will happen later when the 533 * prepare() memop is called. 534 */ 535 if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir, 536 DMA_ATTR_SKIP_CPU_SYNC)) { 537 pr_err("failed to map scatterlist\n"); 538 ret = -EIO; 539 goto fail_sgt_init; 540 } 541 542 contig_size = vb2_dc_get_contiguous_size(sgt); 543 if (contig_size < size) { 544 pr_err("contiguous mapping is too small %lu/%lu\n", 545 contig_size, size); 546 ret = -EFAULT; 547 goto fail_map_sg; 548 } 549 550 buf->dma_addr = sg_dma_address(sgt->sgl); 551 buf->dma_sgt = sgt; 552out: 553 buf->size = size; 554 555 return buf; 556 557fail_map_sg: 558 dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC); 559 560fail_sgt_init: 561 sg_free_table(sgt); 562 563fail_sgt: 564 kfree(sgt); 565 566fail_pfnvec: 567 vb2_destroy_framevec(vec); 568 569fail_buf: 570 kfree(buf); 571 572 return ERR_PTR(ret); 573} 574 575/*********************************************/ 576/* callbacks for DMABUF buffers */ 577/*********************************************/ 578 579static int vb2_dc_map_dmabuf(void *mem_priv) 580{ 581 struct vb2_dc_buf *buf = mem_priv; 582 struct sg_table *sgt; 583 unsigned long contig_size; 584 585 if (WARN_ON(!buf->db_attach)) { 586 pr_err("trying to pin a non attached buffer\n"); 587 return -EINVAL; 588 } 589 590 if (WARN_ON(buf->dma_sgt)) { 591 pr_err("dmabuf buffer is already pinned\n"); 592 return 0; 593 } 594 595 /* get the associated scatterlist for this buffer */ 596 sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir); 597 if (IS_ERR(sgt)) { 598 pr_err("Error getting dmabuf scatterlist\n"); 599 return -EINVAL; 600 } 601 602 /* checking if dmabuf is big enough to store contiguous chunk */ 603 contig_size = vb2_dc_get_contiguous_size(sgt); 604 if (contig_size < buf->size) { 605 pr_err("contiguous chunk is too small %lu/%lu\n", 606 contig_size, buf->size); 607 dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir); 608 return -EFAULT; 609 } 610 611 buf->dma_addr = sg_dma_address(sgt->sgl); 612 buf->dma_sgt = sgt; 613 buf->vaddr = NULL; 614 615 return 0; 616} 617 618static void vb2_dc_unmap_dmabuf(void *mem_priv) 619{ 620 struct vb2_dc_buf *buf = mem_priv; 621 struct sg_table *sgt = buf->dma_sgt; 622 623 if (WARN_ON(!buf->db_attach)) { 624 pr_err("trying to unpin a not attached buffer\n"); 625 return; 626 } 627 628 if (WARN_ON(!sgt)) { 629 pr_err("dmabuf buffer is already unpinned\n"); 630 return; 631 } 632 633 if (buf->vaddr) { 634 dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr); 635 buf->vaddr = NULL; 636 } 637 dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir); 638 639 buf->dma_addr = 0; 640 buf->dma_sgt = NULL; 641} 642 643static void vb2_dc_detach_dmabuf(void *mem_priv) 644{ 645 struct vb2_dc_buf *buf = mem_priv; 646 647 /* if vb2 works correctly you should never detach mapped buffer */ 648 if (WARN_ON(buf->dma_addr)) 649 vb2_dc_unmap_dmabuf(buf); 650 651 /* detach this attachment */ 652 dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach); 653 kfree(buf); 654} 655 656static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf, 657 unsigned long size, enum dma_data_direction dma_dir) 658{ 659 struct vb2_dc_buf *buf; 660 struct dma_buf_attachment *dba; 661 662 if (dbuf->size < size) 663 return ERR_PTR(-EFAULT); 664 665 if (WARN_ON(!dev)) 666 return ERR_PTR(-EINVAL); 667 668 buf = kzalloc(sizeof(*buf), GFP_KERNEL); 669 if (!buf) 670 return ERR_PTR(-ENOMEM); 671 672 buf->dev = dev; 673 /* create attachment for the dmabuf with the user device */ 674 dba = dma_buf_attach(dbuf, buf->dev); 675 if (IS_ERR(dba)) { 676 pr_err("failed to attach dmabuf\n"); 677 kfree(buf); 678 return dba; 679 } 680 681 buf->dma_dir = dma_dir; 682 buf->size = size; 683 buf->db_attach = dba; 684 685 return buf; 686} 687 688/*********************************************/ 689/* DMA CONTIG exported functions */ 690/*********************************************/ 691 692const struct vb2_mem_ops vb2_dma_contig_memops = { 693 .alloc = vb2_dc_alloc, 694 .put = vb2_dc_put, 695 .get_dmabuf = vb2_dc_get_dmabuf, 696 .cookie = vb2_dc_cookie, 697 .vaddr = vb2_dc_vaddr, 698 .mmap = vb2_dc_mmap, 699 .get_userptr = vb2_dc_get_userptr, 700 .put_userptr = vb2_dc_put_userptr, 701 .prepare = vb2_dc_prepare, 702 .finish = vb2_dc_finish, 703 .map_dmabuf = vb2_dc_map_dmabuf, 704 .unmap_dmabuf = vb2_dc_unmap_dmabuf, 705 .attach_dmabuf = vb2_dc_attach_dmabuf, 706 .detach_dmabuf = vb2_dc_detach_dmabuf, 707 .num_users = vb2_dc_num_users, 708}; 709EXPORT_SYMBOL_GPL(vb2_dma_contig_memops); 710 711/** 712 * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size 713 * @dev: device for configuring DMA parameters 714 * @size: size of DMA max segment size to set 715 * 716 * To allow mapping the scatter-list into a single chunk in the DMA 717 * address space, the device is required to have the DMA max segment 718 * size parameter set to a value larger than the buffer size. Otherwise, 719 * the DMA-mapping subsystem will split the mapping into max segment 720 * size chunks. This function sets the DMA max segment size 721 * parameter to let DMA-mapping map a buffer as a single chunk in DMA 722 * address space. 723 * This code assumes that the DMA-mapping subsystem will merge all 724 * scatterlist segments if this is really possible (for example when 725 * an IOMMU is available and enabled). 726 * Ideally, this parameter should be set by the generic bus code, but it 727 * is left with the default 64KiB value due to historical litmiations in 728 * other subsystems (like limited USB host drivers) and there no good 729 * place to set it to the proper value. 730 * This function should be called from the drivers, which are known to 731 * operate on platforms with IOMMU and provide access to shared buffers 732 * (either USERPTR or DMABUF). This should be done before initializing 733 * videobuf2 queue. 734 */ 735int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size) 736{ 737 if (!dev->dma_parms) { 738 dev_err(dev, "Failed to set max_seg_size: dma_parms is NULL\n"); 739 return -ENODEV; 740 } 741 if (dma_get_max_seg_size(dev) < size) 742 return dma_set_max_seg_size(dev, size); 743 744 return 0; 745} 746EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size); 747 748MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2"); 749MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>"); 750MODULE_LICENSE("GPL"); 751