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_sg(sgt->sgl, s, sgt->nents, i) {
  57                 if (sg_dma_address(s) != expected)
  58                         break;
  59                 expected = sg_dma_address(s) + 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
  80         if (!buf->vaddr && buf->db_attach)
  81                 buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
  82
  83         return buf->vaddr;
  84 }
  85
  86 static 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
  93 static 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         /* DMABUF exporter will flush the cache for us */
  99         if (!sgt || buf->db_attach)
 100                 return;
 101
 102         dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
 103                                buf->dma_dir);
 104 }
 105
 106 static void vb2_dc_finish(void *buf_priv)
 107 {
 108         struct vb2_dc_buf *buf = buf_priv;
 109         struct sg_table *sgt = buf->dma_sgt;
 110
 111         /* DMABUF exporter will flush the cache for us */
 112         if (!sgt || buf->db_attach)
 113                 return;
 114
 115         dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
 116 }
 117
 118 /*********************************************/
 119 /*        callbacks for MMAP buffers         */
 120 /*********************************************/
 121
 122 static void vb2_dc_put(void *buf_priv)
 123 {
 124         struct vb2_dc_buf *buf = buf_priv;
 125
 126         if (!refcount_dec_and_test(&buf->refcount))
 127                 return;
 128
 129         if (buf->sgt_base) {
 130                 sg_free_table(buf->sgt_base);
 131                 kfree(buf->sgt_base);
 132         }
 133         dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr,
 134                        buf->attrs);
 135         put_device(buf->dev);
 136         kfree(buf);
 137 }
 138
 139 static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
 140                           unsigned long size, enum dma_data_direction dma_dir,
 141                           gfp_t gfp_flags)
 142 {
 143         struct vb2_dc_buf *buf;
 144
 145         if (WARN_ON(!dev))
 146                 return ERR_PTR(-EINVAL);
 147
 148         buf = kzalloc(sizeof *buf, GFP_KERNEL);
 149         if (!buf)
 150                 return ERR_PTR(-ENOMEM);
 151
 152         if (attrs)
 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_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
 277                                    attach->dma_dir, 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_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
 303                                    attach->dma_dir, 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         sgt->nents = dma_map_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
 312                                       dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 313         if (!sgt->nents) {
 314                 pr_err("failed to map scatterlist\n");
 315                 mutex_unlock(lock);
 316                 return ERR_PTR(-EIO);
 317         }
 318
 319         attach->dma_dir = dma_dir;
 320
 321         mutex_unlock(lock);
 322
 323         return sgt;
 324 }
 325
 326 static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
 327         struct sg_table *sgt, enum dma_data_direction dma_dir)
 328 {
 329         /* nothing to be done here */
 330 }
 331
 332 static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
 333 {
 334         /* drop reference obtained in vb2_dc_get_dmabuf */
 335         vb2_dc_put(dbuf->priv);
 336 }
 337
 338 static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
 339 {
 340         struct vb2_dc_buf *buf = dbuf->priv;
 341
 342         return buf->vaddr;
 343 }
 344
 345 static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
 346         struct vm_area_struct *vma)
 347 {
 348         return vb2_dc_mmap(dbuf->priv, vma);
 349 }
 350
 351 static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
 352         .attach = vb2_dc_dmabuf_ops_attach,
 353         .detach = vb2_dc_dmabuf_ops_detach,
 354         .map_dma_buf = vb2_dc_dmabuf_ops_map,
 355         .unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
 356         .vmap = vb2_dc_dmabuf_ops_vmap,
 357         .mmap = vb2_dc_dmabuf_ops_mmap,
 358         .release = vb2_dc_dmabuf_ops_release,
 359 };
 360
 361 static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
 362 {
 363         int ret;
 364         struct sg_table *sgt;
 365
 366         sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
 367         if (!sgt) {
 368                 dev_err(buf->dev, "failed to alloc sg table\n");
 369                 return NULL;
 370         }
 371
 372         ret = dma_get_sgtable_attrs(buf->dev, sgt, buf->cookie, buf->dma_addr,
 373                 buf->size, buf->attrs);
 374         if (ret < 0) {
 375                 dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
 376                 kfree(sgt);
 377                 return NULL;
 378         }
 379
 380         return sgt;
 381 }
 382
 383 static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
 384 {
 385         struct vb2_dc_buf *buf = buf_priv;
 386         struct dma_buf *dbuf;
 387         DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 388
 389         exp_info.ops = &vb2_dc_dmabuf_ops;
 390         exp_info.size = buf->size;
 391         exp_info.flags = flags;
 392         exp_info.priv = buf;
 393
 394         if (!buf->sgt_base)
 395                 buf->sgt_base = vb2_dc_get_base_sgt(buf);
 396
 397         if (WARN_ON(!buf->sgt_base))
 398                 return NULL;
 399
 400         dbuf = dma_buf_export(&exp_info);
 401         if (IS_ERR(dbuf))
 402                 return NULL;
 403
 404         /* dmabuf keeps reference to vb2 buffer */
 405         refcount_inc(&buf->refcount);
 406
 407         return dbuf;
 408 }
 409
 410 /*********************************************/
 411 /*       callbacks for USERPTR buffers       */
 412 /*********************************************/
 413
 414 static void vb2_dc_put_userptr(void *buf_priv)
 415 {
 416         struct vb2_dc_buf *buf = buf_priv;
 417         struct sg_table *sgt = buf->dma_sgt;
 418         int i;
 419         struct page **pages;
 420
 421         if (sgt) {
 422                 /*
 423                  * No need to sync to CPU, it's already synced to the CPU
 424                  * since the finish() memop will have been called before this.
 425                  */
 426                 dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
 427                                    buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 428                 pages = frame_vector_pages(buf->vec);
 429                 /* sgt should exist only if vector contains pages... */
 430                 BUG_ON(IS_ERR(pages));
 431                 if (buf->dma_dir == DMA_FROM_DEVICE ||
 432                     buf->dma_dir == DMA_BIDIRECTIONAL)
 433                         for (i = 0; i < frame_vector_count(buf->vec); i++)
 434                                 set_page_dirty_lock(pages[i]);
 435                 sg_free_table(sgt);
 436                 kfree(sgt);
 437         } else {
 438                 dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
 439                                    buf->dma_dir, 0);
 440         }
 441         vb2_destroy_framevec(buf->vec);
 442         kfree(buf);
 443 }
 444
 445 static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 446         unsigned long size, enum dma_data_direction dma_dir)
 447 {
 448         struct vb2_dc_buf *buf;
 449         struct frame_vector *vec;
 450         unsigned int offset;
 451         int n_pages, i;
 452         int ret = 0;
 453         struct sg_table *sgt;
 454         unsigned long contig_size;
 455         unsigned long dma_align = dma_get_cache_alignment();
 456
 457         /* Only cache aligned DMA transfers are reliable */
 458         if (!IS_ALIGNED(vaddr | size, dma_align)) {
 459                 pr_debug("user data must be aligned to %lu bytes\n", dma_align);
 460                 return ERR_PTR(-EINVAL);
 461         }
 462
 463         if (!size) {
 464                 pr_debug("size is zero\n");
 465                 return ERR_PTR(-EINVAL);
 466         }
 467
 468         if (WARN_ON(!dev))
 469                 return ERR_PTR(-EINVAL);
 470
 471         buf = kzalloc(sizeof *buf, GFP_KERNEL);
 472         if (!buf)
 473                 return ERR_PTR(-ENOMEM);
 474
 475         buf->dev = dev;
 476         buf->dma_dir = dma_dir;
 477
 478         offset = lower_32_bits(offset_in_page(vaddr));
 479         vec = vb2_create_framevec(vaddr, size);
 480         if (IS_ERR(vec)) {
 481                 ret = PTR_ERR(vec);
 482                 goto fail_buf;
 483         }
 484         buf->vec = vec;
 485         n_pages = frame_vector_count(vec);
 486         ret = frame_vector_to_pages(vec);
 487         if (ret < 0) {
 488                 unsigned long *nums = frame_vector_pfns(vec);
 489
 490                 /*
 491                  * Failed to convert to pages... Check the memory is physically
 492                  * contiguous and use direct mapping
 493                  */
 494                 for (i = 1; i < n_pages; i++)
 495                         if (nums[i-1] + 1 != nums[i])
 496                                 goto fail_pfnvec;
 497                 buf->dma_addr = dma_map_resource(buf->dev,
 498                                 __pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
 499                 if (dma_mapping_error(buf->dev, buf->dma_addr)) {
 500                         ret = -ENOMEM;
 501                         goto fail_pfnvec;
 502                 }
 503                 goto out;
 504         }
 505
 506         sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
 507         if (!sgt) {
 508                 pr_err("failed to allocate sg table\n");
 509                 ret = -ENOMEM;
 510                 goto fail_pfnvec;
 511         }
 512
 513         ret = sg_alloc_table_from_pages(sgt, frame_vector_pages(vec), n_pages,
 514                 offset, size, GFP_KERNEL);
 515         if (ret) {
 516                 pr_err("failed to initialize sg table\n");
 517                 goto fail_sgt;
 518         }
 519
 520         /*
 521          * No need to sync to the device, this will happen later when the
 522          * prepare() memop is called.
 523          */
 524         sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
 525                                       buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 526         if (sgt->nents <= 0) {
 527                 pr_err("failed to map scatterlist\n");
 528                 ret = -EIO;
 529                 goto fail_sgt_init;
 530         }
 531
 532         contig_size = vb2_dc_get_contiguous_size(sgt);
 533         if (contig_size < size) {
 534                 pr_err("contiguous mapping is too small %lu/%lu\n",
 535                         contig_size, size);
 536                 ret = -EFAULT;
 537                 goto fail_map_sg;
 538         }
 539
 540         buf->dma_addr = sg_dma_address(sgt->sgl);
 541         buf->dma_sgt = sgt;
 542 out:
 543         buf->size = size;
 544
 545         return buf;
 546
 547 fail_map_sg:
 548         dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
 549                            buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
 550
 551 fail_sgt_init:
 552         sg_free_table(sgt);
 553
 554 fail_sgt:
 555         kfree(sgt);
 556
 557 fail_pfnvec:
 558         vb2_destroy_framevec(vec);
 559
 560 fail_buf:
 561         kfree(buf);
 562
 563         return ERR_PTR(ret);
 564 }
 565
 566 /*********************************************/
 567 /*       callbacks for DMABUF buffers        */
 568 /*********************************************/
 569
 570 static int vb2_dc_map_dmabuf(void *mem_priv)
 571 {
 572         struct vb2_dc_buf *buf = mem_priv;
 573         struct sg_table *sgt;
 574         unsigned long contig_size;
 575
 576         if (WARN_ON(!buf->db_attach)) {
 577                 pr_err("trying to pin a non attached buffer\n");
 578                 return -EINVAL;
 579         }
 580
 581         if (WARN_ON(buf->dma_sgt)) {
 582                 pr_err("dmabuf buffer is already pinned\n");
 583                 return 0;
 584         }
 585
 586         /* get the associated scatterlist for this buffer */
 587         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
 588         if (IS_ERR(sgt)) {
 589                 pr_err("Error getting dmabuf scatterlist\n");
 590                 return -EINVAL;
 591         }
 592
 593         /* checking if dmabuf is big enough to store contiguous chunk */
 594         contig_size = vb2_dc_get_contiguous_size(sgt);
 595         if (contig_size < buf->size) {
 596                 pr_err("contiguous chunk is too small %lu/%lu b\n",
 597                         contig_size, buf->size);
 598                 dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
 599                 return -EFAULT;
 600         }
 601
 602         buf->dma_addr = sg_dma_address(sgt->sgl);
 603         buf->dma_sgt = sgt;
 604         buf->vaddr = NULL;
 605
 606         return 0;
 607 }
 608
 609 static void vb2_dc_unmap_dmabuf(void *mem_priv)
 610 {
 611         struct vb2_dc_buf *buf = mem_priv;
 612         struct sg_table *sgt = buf->dma_sgt;
 613
 614         if (WARN_ON(!buf->db_attach)) {
 615                 pr_err("trying to unpin a not attached buffer\n");
 616                 return;
 617         }
 618
 619         if (WARN_ON(!sgt)) {
 620                 pr_err("dmabuf buffer is already unpinned\n");
 621                 return;
 622         }
 623
 624         if (buf->vaddr) {
 625                 dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr);
 626                 buf->vaddr = NULL;
 627         }
 628         dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
 629
 630         buf->dma_addr = 0;
 631         buf->dma_sgt = NULL;
 632 }
 633
 634 static void vb2_dc_detach_dmabuf(void *mem_priv)
 635 {
 636         struct vb2_dc_buf *buf = mem_priv;
 637
 638         /* if vb2 works correctly you should never detach mapped buffer */
 639         if (WARN_ON(buf->dma_addr))
 640                 vb2_dc_unmap_dmabuf(buf);
 641
 642         /* detach this attachment */
 643         dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
 644         kfree(buf);
 645 }
 646
 647 static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
 648         unsigned long size, enum dma_data_direction dma_dir)
 649 {
 650         struct vb2_dc_buf *buf;
 651         struct dma_buf_attachment *dba;
 652
 653         if (dbuf->size < size)
 654                 return ERR_PTR(-EFAULT);
 655
 656         if (WARN_ON(!dev))
 657                 return ERR_PTR(-EINVAL);
 658
 659         buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 660         if (!buf)
 661                 return ERR_PTR(-ENOMEM);
 662
 663         buf->dev = dev;
 664         /* create attachment for the dmabuf with the user device */
 665         dba = dma_buf_attach(dbuf, buf->dev);
 666         if (IS_ERR(dba)) {
 667                 pr_err("failed to attach dmabuf\n");
 668                 kfree(buf);
 669                 return dba;
 670         }
 671
 672         buf->dma_dir = dma_dir;
 673         buf->size = size;
 674         buf->db_attach = dba;
 675
 676         return buf;
 677 }
 678
 679 /*********************************************/
 680 /*       DMA CONTIG exported functions       */
 681 /*********************************************/
 682
 683 const struct vb2_mem_ops vb2_dma_contig_memops = {
 684         .alloc          = vb2_dc_alloc,
 685         .put            = vb2_dc_put,
 686         .get_dmabuf     = vb2_dc_get_dmabuf,
 687         .cookie         = vb2_dc_cookie,
 688         .vaddr          = vb2_dc_vaddr,
 689         .mmap           = vb2_dc_mmap,
 690         .get_userptr    = vb2_dc_get_userptr,
 691         .put_userptr    = vb2_dc_put_userptr,
 692         .prepare        = vb2_dc_prepare,
 693         .finish         = vb2_dc_finish,
 694         .map_dmabuf     = vb2_dc_map_dmabuf,
 695         .unmap_dmabuf   = vb2_dc_unmap_dmabuf,
 696         .attach_dmabuf  = vb2_dc_attach_dmabuf,
 697         .detach_dmabuf  = vb2_dc_detach_dmabuf,
 698         .num_users      = vb2_dc_num_users,
 699 };
 700 EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
 701
 702 /**
 703  * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size
 704  * @dev:        device for configuring DMA parameters
 705  * @size:       size of DMA max segment size to set
 706  *
 707  * To allow mapping the scatter-list into a single chunk in the DMA
 708  * address space, the device is required to have the DMA max segment
 709  * size parameter set to a value larger than the buffer size. Otherwise,
 710  * the DMA-mapping subsystem will split the mapping into max segment
 711  * size chunks. This function sets the DMA max segment size
 712  * parameter to let DMA-mapping map a buffer as a single chunk in DMA
 713  * address space.
 714  * This code assumes that the DMA-mapping subsystem will merge all
 715  * scatterlist segments if this is really possible (for example when
 716  * an IOMMU is available and enabled).
 717  * Ideally, this parameter should be set by the generic bus code, but it
 718  * is left with the default 64KiB value due to historical litmiations in
 719  * other subsystems (like limited USB host drivers) and there no good
 720  * place to set it to the proper value.
 721  * This function should be called from the drivers, which are known to
 722  * operate on platforms with IOMMU and provide access to shared buffers
 723  * (either USERPTR or DMABUF). This should be done before initializing
 724  * videobuf2 queue.
 725  */
 726 int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
 727 {
 728         if (!dev->dma_parms) {
 729                 dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
 730                 if (!dev->dma_parms)
 731                         return -ENOMEM;
 732         }
 733         if (dma_get_max_seg_size(dev) < size)
 734                 return dma_set_max_seg_size(dev, size);
 735
 736         return 0;
 737 }
 738 EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
 739
 740 /*
 741  * vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
 742  * @dev:        device for configuring DMA parameters
 743  *
 744  * This function releases resources allocated to configure DMA parameters
 745  * (see vb2_dma_contig_set_max_seg_size() function). It should be called from
 746  * device drivers on driver remove.
 747  */
 748 void vb2_dma_contig_clear_max_seg_size(struct device *dev)
 749 {
 750         kfree(dev->dma_parms);
 751         dev->dma_parms = NULL;
 752 }
 753 EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_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");