drivers/media/common/videobuf2/videobuf2-dma-contig.c

   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
  25 struct 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
  49 static 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
  69 static void *vb2_dc_cookie(void *buf_priv)
  70 {
  71         struct vb2_dc_buf *buf = buf_priv;
  72
  73         return &buf->dma_addr;
  74 }
  75
  76 static void *vb2_dc_vaddr(void *buf_priv)
  77 {
  78         struct vb2_dc_buf *buf = buf_priv;
  79         struct dma_buf_map map;
  80         int ret;
  81
  82         if (!buf->vaddr && buf->db_attach) {
  83                 ret = dma_buf_vmap(buf->db_attach->dmabuf, &map);
  84                 buf->vaddr = ret ? NULL : map.vaddr;
  85         }
  86
  87         return buf->vaddr;
  88 }
  89
  90 static unsigned int vb2_dc_num_users(void *buf_priv)
  91 {
  92         struct vb2_dc_buf *buf = buf_priv;
  93
  94         return refcount_read(&buf->refcount);
  95 }
  96
  97 static void vb2_dc_prepare(void *buf_priv)
  98 {
  99         struct vb2_dc_buf *buf = buf_priv;
 100         struct sg_table *sgt = buf->dma_sgt;
 101
 102         if (!sgt)
 103                 return;
 104
 105         dma_sync_sgtable_for_device(buf->dev, sgt, buf->dma_dir);
 106 }
 107
 108 static void vb2_dc_finish(void *buf_priv)
 109 {
 110         struct vb2_dc_buf *buf = buf_priv;
 111         struct sg_table *sgt = buf->dma_sgt;
 112
 113         if (!sgt)
 114                 return;
 115
 116         dma_sync_sgtable_for_cpu(buf->dev, sgt, buf->dma_dir);
 117 }
 118
 119 /*********************************************/
 120 /*        callbacks for MMAP buffers         */
 121 /*********************************************/
 122
 123 static void vb2_dc_put(void *buf_priv)
 124 {
 125         struct vb2_dc_buf *buf = buf_priv;
 126
 127         if (!refcount_dec_and_test(&buf->refcount))
 128                 return;
 129
 130         if (buf->sgt_base) {
 131                 sg_free_table(buf->sgt_base);
 132                 kfree(buf->sgt_base);
 133         }
 134         dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr,
 135                        buf->attrs);
 136         put_device(buf->dev);
 137         kfree(buf);
 138 }
 139
 140 static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
 141                           unsigned long size, enum dma_data_direction dma_dir,
 142                           gfp_t gfp_flags)
 143 {
 144         struct vb2_dc_buf *buf;
 145
 146         if (WARN_ON(!dev))
 147                 return ERR_PTR(-EINVAL);
 148
 149         buf = kzalloc(sizeof *buf, GFP_KERNEL);
 150         if (!buf)
 151                 return ERR_PTR(-ENOMEM);
 152
 153         buf->attrs = attrs;
 154         buf->cookie = dma_alloc_attrs(dev, size, &buf->dma_addr,
 155                                         GFP_KERNEL | gfp_flags, buf->attrs);
 156         if (!buf->cookie) {
 157                 dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
 158                 kfree(buf);
 159                 return ERR_PTR(-ENOMEM);
 160         }
 161
 162         if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
 163                 buf->vaddr = buf->cookie;
 164
 165         /* Prevent the device from being released while the buffer is used */
 166         buf->dev = get_device(dev);
 167         buf->size = size;
 168         buf->dma_dir = dma_dir;
 169
 170         buf->handler.refcount = &buf->refcount;
 171         buf->handler.put = vb2_dc_put;
 172         buf->handler.arg = buf;
 173
 174         refcount_set(&buf->refcount, 1);
 175
 176         return buf;
 177 }
 178
 179 static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
 180 {
 181         struct vb2_dc_buf *buf = buf_priv;
 182         int ret;
 183
 184         if (!buf) {
 185                 printk(KERN_ERR "No buffer to map\n");
 186                 return -EINVAL;
 187         }
 188
 189         ret = dma_mmap_attrs(buf->dev, vma, buf->cookie,
 190                 buf->dma_addr, buf->size, buf->attrs);
 191
 192         if (ret) {
 193                 pr_err("Remapping memory failed, error: %d\n", ret);
 194                 return ret;
 195         }
 196
 197         vma->vm_flags           |= VM_DONTEXPAND | VM_DONTDUMP;
 198         vma->vm_private_data    = &buf->handler;
 199         vma->vm_ops             = &vb2_common_vm_ops;
 200
 201         vma->vm_ops->open(vma);
 202
 203         pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n",
 204                 __func__, (unsigned long)buf->dma_addr, vma->vm_start,
 205                 buf->size);
 206
 207         return 0;
 208 }
 209
 210 /*********************************************/
 211 /*         DMABUF ops for exporters          */
 212 /*********************************************/
 213
 214 struct vb2_dc_attachment {
 215         struct sg_table sgt;
 216         enum dma_data_direction dma_dir;
 217 };
 218
 219 static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf,
 220         struct dma_buf_attachment *dbuf_attach)
 221 {
 222         struct vb2_dc_attachment *attach;
 223         unsigned int i;
 224         struct scatterlist *rd, *wr;
 225         struct sg_table *sgt;
 226         struct vb2_dc_buf *buf = dbuf->priv;
 227         int ret;
 228
 229         attach = kzalloc(sizeof(*attach), GFP_KERNEL);
 230         if (!attach)
 231                 return -ENOMEM;
 232
 233         sgt = &attach->sgt;
 234         /* Copy the buf->base_sgt scatter list to the attachment, as we can't
 235          * map the same scatter list to multiple attachments at the same time.
 236          */
 237         ret = sg_alloc_table(sgt, buf->sgt_base->orig_nents, GFP_KERNEL);
 238         if (ret) {
 239                 kfree(attach);
 240                 return -ENOMEM;
 241         }
 242
 243         rd = buf->sgt_base->sgl;
 244         wr = sgt->sgl;
 245         for (i = 0; i < sgt->orig_nents; ++i) {
 246                 sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
 247                 rd = sg_next(rd);
 248                 wr = sg_next(wr);
 249         }
 250
 251         attach->dma_dir = DMA_NONE;
 252         dbuf_attach->priv = attach;
 253
 254         return 0;
 255 }
 256
 257 static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
 258         struct dma_buf_attachment *db_attach)
 259 {
 260         struct vb2_dc_attachment *attach = db_attach->priv;
 261         struct sg_table *sgt;
 262
 263         if (!attach)
 264                 return;
 265
 266         sgt = &attach->sgt;
 267
 268         /* release the scatterlist cache */
 269         if (attach->dma_dir != DMA_NONE)
 270                 /*
 271                  * Cache sync can be skipped here, as the vb2_dc memory is
 272                  * allocated from device coherent memory, which means the
 273                  * memory locations do not require any explicit cache
 274                  * maintenance prior or after being used by the device.
 275                  */
 276                 dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
 277                                   DMA_ATTR_SKIP_CPU_SYNC);
 278         sg_free_table(sgt);
 279         kfree(attach);
 280         db_attach->priv = NULL;
 281 }
 282
 283 static struct sg_table *vb2_dc_dmabuf_ops_map(
 284         struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
 285 {
 286         struct vb2_dc_attachment *attach = db_attach->priv;
 287         /* stealing dmabuf mutex to serialize map/unmap operations */
 288         struct mutex *lock = &db_attach->dmabuf->lock;
 289         struct sg_table *sgt;
 290
 291         mutex_lock(lock);
 292
 293         sgt = &attach->sgt;
 294         /* return previously mapped sg table */
 295         if (attach->dma_dir == dma_dir) {
 296                 mutex_unlock(lock);
 297                 return sgt;
 298         }
 299
 300         /* release any previous cache */
 301         if (attach->dma_dir != DMA_NONE) {
 302                 dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
 303                                   DMA_ATTR_SKIP_CPU_SYNC);
 304                 attach->dma_dir = DMA_NONE;
 305         }
 306
 307         /*
 308          * mapping to the client with new direction, no cache sync
 309          * required see comment in vb2_dc_dmabuf_ops_detach()
 310          */
 311         if (dma_map_sgtable(db_attach->dev, sgt, dma_dir,
 312                             DMA_ATTR_SKIP_CPU_SYNC)) {
 313                 pr_err("failed to map scatterlist\n");
 314                 mutex_unlock(lock);
 315                 return ERR_PTR(-EIO);
 316         }
 317
 318         attach->dma_dir = dma_dir;
 319
 320         mutex_unlock(lock);
 321
 322         return sgt;
 323 }
 324
 325 static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
 326         struct sg_table *sgt, enum dma_data_direction dma_dir)
 327 {
 328         /* nothing to be done here */
 329 }
 330
 331 static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
 332 {
 333         /* drop reference obtained in vb2_dc_get_dmabuf */
 334         vb2_dc_put(dbuf->priv);
 335 }
 336
 337 static int
 338 vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
 339                                    enum dma_data_direction direction)
 340 {
 341         return 0;
 342 }
 343
 344 static int
 345 vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
 346                                  enum dma_data_direction direction)
 347 {
 348         return 0;
 349 }
 350
 351 static int vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf, struct dma_buf_map *map)
 352 {
 353         struct vb2_dc_buf *buf = dbuf->priv;
 354
 355         dma_buf_map_set_vaddr(map, buf->vaddr);
 356
 357         return 0;
 358 }
 359
 360 static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
 361         struct vm_area_struct *vma)
 362 {
 363         return vb2_dc_mmap(dbuf->priv, vma);
 364 }
 365
 366 static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
 367         .attach = vb2_dc_dmabuf_ops_attach,
 368         .detach = vb2_dc_dmabuf_ops_detach,
 369         .map_dma_buf = vb2_dc_dmabuf_ops_map,
 370         .unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
 371         .begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access,
 372         .end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access,
 373         .vmap = vb2_dc_dmabuf_ops_vmap,
 374         .mmap = vb2_dc_dmabuf_ops_mmap,
 375         .release = vb2_dc_dmabuf_ops_release,
 376 };
 377
 378 static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
 379 {
 380         int ret;
 381         struct sg_table *sgt;
 382
 383         sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
 384         if (!sgt) {
 385                 dev_err(buf->dev, "failed to alloc sg table\n");
 386                 return NULL;
 387         }
 388
 389         ret = dma_get_sgtable_attrs(buf->dev, sgt, buf->cookie, buf->dma_addr,
 390                 buf->size, buf->attrs);
 391         if (ret < 0) {
 392                 dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
 393                 kfree(sgt);
 394                 return NULL;
 395         }
 396
 397         return sgt;
 398 }
 399
 400 static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
 401 {
 402         struct vb2_dc_buf *buf = buf_priv;
 403         struct dma_buf *dbuf;
 404         DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 405
 406         exp_info.ops = &vb2_dc_dmabuf_ops;
 407         exp_info.size = buf->size;
 408         exp_info.flags = flags;
 409         exp_info.priv = buf;
 410
 411         if (!buf->sgt_base)
 412                 buf->sgt_base = vb2_dc_get_base_sgt(buf);
 413
 414         if (WARN_ON(!buf->sgt_base))
 415                 return NULL;
 416
 417         dbuf = dma_buf_export(&exp_info);
 418         if (IS_ERR(dbuf))
 419                 return NULL;
 420
 421         /* dmabuf keeps reference to vb2 buffer */
 422         refcount_inc(&buf->refcount);
 423
 424         return dbuf;
 425 }
 426
 427 /*********************************************/
 428 /*       callbacks for USERPTR buffers       */
 429 /*********************************************/
 430
 431 static void vb2_dc_put_userptr(void *buf_priv)
 432 {
 433         struct vb2_dc_buf *buf = buf_priv;
 434         struct sg_table *sgt = buf->dma_sgt;
 435         int i;
 436         struct page **pages;
 437
 438         if (sgt) {
 439                 /*
 440                  * No need to sync to CPU, it's already synced to the CPU
 441                  * since the finish() memop will have been called before this.
 442                  */
 443                 dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir,
 444                                   DMA_ATTR_SKIP_CPU_SYNC);
 445                 pages = frame_vector_pages(buf->vec);
 446                 /* sgt should exist only if vector contains pages... */
 447                 BUG_ON(IS_ERR(pages));
 448                 if (buf->dma_dir == DMA_FROM_DEVICE ||
 449                     buf->dma_dir == DMA_BIDIRECTIONAL)
 450                         for (i = 0; i < frame_vector_count(buf->vec); i++)
 451                                 set_page_dirty_lock(pages[i]);
 452                 sg_free_table(sgt);
 453                 kfree(sgt);
 454         } else {
 455                 dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
 456                                    buf->dma_dir, 0);
 457         }
 458         vb2_destroy_framevec(buf->vec);
 459         kfree(buf);
 460 }
 461
 462 static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 463         unsigned long size, enum dma_data_direction dma_dir)
 464 {
 465         struct vb2_dc_buf *buf;
 466         struct frame_vector *vec;
 467         unsigned int offset;
 468         int n_pages, i;
 469         int ret = 0;
 470         struct sg_table *sgt;
 471         unsigned long contig_size;
 472         unsigned long dma_align = dma_get_cache_alignment();
 473
 474         /* Only cache aligned DMA transfers are reliable */
 475         if (!IS_ALIGNED(vaddr | size, dma_align)) {
 476                 pr_debug("user data must be aligned to %lu bytes\n", dma_align);
 477                 return ERR_PTR(-EINVAL);
 478         }
 479
 480         if (!size) {
 481                 pr_debug("size is zero\n");
 482                 return ERR_PTR(-EINVAL);
 483         }
 484
 485         if (WARN_ON(!dev))
 486                 return ERR_PTR(-EINVAL);
 487
 488         buf = kzalloc(sizeof *buf, GFP_KERNEL);
 489         if (!buf)
 490                 return ERR_PTR(-ENOMEM);
 491
 492         buf->dev = dev;
 493         buf->dma_dir = dma_dir;
 494
 495         offset = lower_32_bits(offset_in_page(vaddr));
 496         vec = vb2_create_framevec(vaddr, size);
 497         if (IS_ERR(vec)) {
 498                 ret = PTR_ERR(vec);
 499                 goto fail_buf;
 500         }
 501         buf->vec = vec;
 502         n_pages = frame_vector_count(vec);
 503         ret = frame_vector_to_pages(vec);
 504         if (ret < 0) {
 505                 unsigned long *nums = frame_vector_pfns(vec);
 506
 507                 /*
 508                  * Failed to convert to pages... Check the memory is physically
 509                  * contiguous and use direct mapping
 510                  */
 511                 for (i = 1; i < n_pages; i++)
 512                         if (nums[i-1] + 1 != nums[i])
 513                                 goto fail_pfnvec;
 514                 buf->dma_addr = dma_map_resource(buf->dev,
 515                                 __pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
 516                 if (dma_mapping_error(buf->dev, buf->dma_addr)) {
 517                         ret = -ENOMEM;
 518                         goto fail_pfnvec;
 519                 }
 520                 goto out;
 521         }
 522
 523         sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
 524         if (!sgt) {
 525                 pr_err("failed to allocate sg table\n");
 526                 ret = -ENOMEM;
 527                 goto fail_pfnvec;
 528         }
 529
 530         ret = sg_alloc_table_from_pages(sgt, frame_vector_pages(vec), n_pages,
 531                 offset, size, GFP_KERNEL);
 532         if (ret) {
 533                 pr_err("failed to initialize sg table\n");
 534                 goto fail_sgt;
 535         }
 536
 537         /*
 538          * No need to sync to the device, this will happen later when the
 539          * prepare() memop is called.
 540          */
 541         if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir,
 542                             DMA_ATTR_SKIP_CPU_SYNC)) {
 543                 pr_err("failed to map scatterlist\n");
 544                 ret = -EIO;
 545                 goto fail_sgt_init;
 546         }
 547
 548         contig_size = vb2_dc_get_contiguous_size(sgt);
 549         if (contig_size < size) {
 550                 pr_err("contiguous mapping is too small %lu/%lu\n",
 551                         contig_size, size);
 552                 ret = -EFAULT;
 553                 goto fail_map_sg;
 554         }
 555
 556         buf->dma_addr = sg_dma_address(sgt->sgl);
 557         buf->dma_sgt = sgt;
 558 out:
 559         buf->size = size;
 560
 561         return buf;
 562
 563 fail_map_sg:
 564         dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 565
 566 fail_sgt_init:
 567         sg_free_table(sgt);
 568
 569 fail_sgt:
 570         kfree(sgt);
 571
 572 fail_pfnvec:
 573         vb2_destroy_framevec(vec);
 574
 575 fail_buf:
 576         kfree(buf);
 577
 578         return ERR_PTR(ret);
 579 }
 580
 581 /*********************************************/
 582 /*       callbacks for DMABUF buffers        */
 583 /*********************************************/
 584
 585 static int vb2_dc_map_dmabuf(void *mem_priv)
 586 {
 587         struct vb2_dc_buf *buf = mem_priv;
 588         struct sg_table *sgt;
 589         unsigned long contig_size;
 590
 591         if (WARN_ON(!buf->db_attach)) {
 592                 pr_err("trying to pin a non attached buffer\n");
 593                 return -EINVAL;
 594         }
 595
 596         if (WARN_ON(buf->dma_sgt)) {
 597                 pr_err("dmabuf buffer is already pinned\n");
 598                 return 0;
 599         }
 600
 601         /* get the associated scatterlist for this buffer */
 602         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
 603         if (IS_ERR(sgt)) {
 604                 pr_err("Error getting dmabuf scatterlist\n");
 605                 return -EINVAL;
 606         }
 607
 608         /* checking if dmabuf is big enough to store contiguous chunk */
 609         contig_size = vb2_dc_get_contiguous_size(sgt);
 610         if (contig_size < buf->size) {
 611                 pr_err("contiguous chunk is too small %lu/%lu\n",
 612                        contig_size, buf->size);
 613                 dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
 614                 return -EFAULT;
 615         }
 616
 617         buf->dma_addr = sg_dma_address(sgt->sgl);
 618         buf->dma_sgt = sgt;
 619         buf->vaddr = NULL;
 620
 621         return 0;
 622 }
 623
 624 static void vb2_dc_unmap_dmabuf(void *mem_priv)
 625 {
 626         struct vb2_dc_buf *buf = mem_priv;
 627         struct sg_table *sgt = buf->dma_sgt;
 628         struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(buf->vaddr);
 629
 630         if (WARN_ON(!buf->db_attach)) {
 631                 pr_err("trying to unpin a not attached buffer\n");
 632                 return;
 633         }
 634
 635         if (WARN_ON(!sgt)) {
 636                 pr_err("dmabuf buffer is already unpinned\n");
 637                 return;
 638         }
 639
 640         if (buf->vaddr) {
 641                 dma_buf_vunmap(buf->db_attach->dmabuf, &map);
 642                 buf->vaddr = NULL;
 643         }
 644         dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
 645
 646         buf->dma_addr = 0;
 647         buf->dma_sgt = NULL;
 648 }
 649
 650 static void vb2_dc_detach_dmabuf(void *mem_priv)
 651 {
 652         struct vb2_dc_buf *buf = mem_priv;
 653
 654         /* if vb2 works correctly you should never detach mapped buffer */
 655         if (WARN_ON(buf->dma_addr))
 656                 vb2_dc_unmap_dmabuf(buf);
 657
 658         /* detach this attachment */
 659         dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
 660         kfree(buf);
 661 }
 662
 663 static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
 664         unsigned long size, enum dma_data_direction dma_dir)
 665 {
 666         struct vb2_dc_buf *buf;
 667         struct dma_buf_attachment *dba;
 668
 669         if (dbuf->size < size)
 670                 return ERR_PTR(-EFAULT);
 671
 672         if (WARN_ON(!dev))
 673                 return ERR_PTR(-EINVAL);
 674
 675         buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 676         if (!buf)
 677                 return ERR_PTR(-ENOMEM);
 678
 679         buf->dev = dev;
 680         /* create attachment for the dmabuf with the user device */
 681         dba = dma_buf_attach(dbuf, buf->dev);
 682         if (IS_ERR(dba)) {
 683                 pr_err("failed to attach dmabuf\n");
 684                 kfree(buf);
 685                 return dba;
 686         }
 687
 688         buf->dma_dir = dma_dir;
 689         buf->size = size;
 690         buf->db_attach = dba;
 691
 692         return buf;
 693 }
 694
 695 /*********************************************/
 696 /*       DMA CONTIG exported functions       */
 697 /*********************************************/
 698
 699 const struct vb2_mem_ops vb2_dma_contig_memops = {
 700         .alloc          = vb2_dc_alloc,
 701         .put            = vb2_dc_put,
 702         .get_dmabuf     = vb2_dc_get_dmabuf,
 703         .cookie         = vb2_dc_cookie,
 704         .vaddr          = vb2_dc_vaddr,
 705         .mmap           = vb2_dc_mmap,
 706         .get_userptr    = vb2_dc_get_userptr,
 707         .put_userptr    = vb2_dc_put_userptr,
 708         .prepare        = vb2_dc_prepare,
 709         .finish         = vb2_dc_finish,
 710         .map_dmabuf     = vb2_dc_map_dmabuf,
 711         .unmap_dmabuf   = vb2_dc_unmap_dmabuf,
 712         .attach_dmabuf  = vb2_dc_attach_dmabuf,
 713         .detach_dmabuf  = vb2_dc_detach_dmabuf,
 714         .num_users      = vb2_dc_num_users,
 715 };
 716 EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
 717
 718 /**
 719  * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size
 720  * @dev:        device for configuring DMA parameters
 721  * @size:       size of DMA max segment size to set
 722  *
 723  * To allow mapping the scatter-list into a single chunk in the DMA
 724  * address space, the device is required to have the DMA max segment
 725  * size parameter set to a value larger than the buffer size. Otherwise,
 726  * the DMA-mapping subsystem will split the mapping into max segment
 727  * size chunks. This function sets the DMA max segment size
 728  * parameter to let DMA-mapping map a buffer as a single chunk in DMA
 729  * address space.
 730  * This code assumes that the DMA-mapping subsystem will merge all
 731  * scatterlist segments if this is really possible (for example when
 732  * an IOMMU is available and enabled).
 733  * Ideally, this parameter should be set by the generic bus code, but it
 734  * is left with the default 64KiB value due to historical litmiations in
 735  * other subsystems (like limited USB host drivers) and there no good
 736  * place to set it to the proper value.
 737  * This function should be called from the drivers, which are known to
 738  * operate on platforms with IOMMU and provide access to shared buffers
 739  * (either USERPTR or DMABUF). This should be done before initializing
 740  * videobuf2 queue.
 741  */
 742 int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 743 {
 744         if (!dev->dma_parms) {
 745                 dev_err(dev, "Failed to set max_seg_size: dma_parms is NULL\n");
 746                 return -ENODEV;
 747         }
 748         if (dma_get_max_seg_size(dev) < size)
 749                 return dma_set_max_seg_size(dev, size);
 750
 751         return 0;
 752 }
 753 EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
 754
 755 MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
 756 MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
 757 MODULE_LICENSE("GPL");