root/drivers/gpu/drm/drm_gem_shmem_helper.c

DEFINITIONS

1. drm_gem_shmem_create
2. drm_gem_shmem_free_object
3. drm_gem_shmem_get_pages_locked
4. drm_gem_shmem_get_pages
5. drm_gem_shmem_put_pages_locked
6. drm_gem_shmem_put_pages
7. drm_gem_shmem_pin
8. drm_gem_shmem_unpin
9. drm_gem_shmem_vmap_locked
10. drm_gem_shmem_vmap
11. drm_gem_shmem_vunmap_locked
12. drm_gem_shmem_vunmap
13. drm_gem_shmem_create_with_handle
14. drm_gem_shmem_madvise
15. drm_gem_shmem_purge_locked
16. drm_gem_shmem_purge
17. drm_gem_shmem_dumb_create
18. drm_gem_shmem_fault
19. drm_gem_shmem_vm_open
20. drm_gem_shmem_vm_close
21. drm_gem_shmem_mmap
22. drm_gem_shmem_print_info
23. drm_gem_shmem_get_sg_table
24. drm_gem_shmem_get_pages_sgt
25. drm_gem_shmem_prime_import_sg_table

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2018 Noralf Trønnes
   4  */
   5 
   6 #include <linux/dma-buf.h>
   7 #include <linux/export.h>
   8 #include <linux/mutex.h>
   9 #include <linux/shmem_fs.h>
  10 #include <linux/slab.h>
  11 #include <linux/vmalloc.h>
  12 
  13 #include <drm/drm.h>
  14 #include <drm/drm_device.h>
  15 #include <drm/drm_drv.h>
  16 #include <drm/drm_gem_shmem_helper.h>
  17 #include <drm/drm_prime.h>
  18 #include <drm/drm_print.h>
  19 
  20 /**
  21  * DOC: overview
  22  *
  23  * This library provides helpers for GEM objects backed by shmem buffers
  24  * allocated using anonymous pageable memory.
  25  */
  26 
  27 static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
  28         .free = drm_gem_shmem_free_object,
  29         .print_info = drm_gem_shmem_print_info,
  30         .pin = drm_gem_shmem_pin,
  31         .unpin = drm_gem_shmem_unpin,
  32         .get_sg_table = drm_gem_shmem_get_sg_table,
  33         .vmap = drm_gem_shmem_vmap,
  34         .vunmap = drm_gem_shmem_vunmap,
  35         .vm_ops = &drm_gem_shmem_vm_ops,
  36 };
  37 
  38 /**
  39  * drm_gem_shmem_create - Allocate an object with the given size
  40  * @dev: DRM device
  41  * @size: Size of the object to allocate
  42  *
  43  * This function creates a shmem GEM object.
  44  *
  45  * Returns:
  46  * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
  47  * error code on failure.
  48  */
  49 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
  50 {
  51         struct drm_gem_shmem_object *shmem;
  52         struct drm_gem_object *obj;
  53         int ret;
  54 
  55         size = PAGE_ALIGN(size);
  56 
  57         if (dev->driver->gem_create_object)
  58                 obj = dev->driver->gem_create_object(dev, size);
  59         else
  60                 obj = kzalloc(sizeof(*shmem), GFP_KERNEL);
  61         if (!obj)
  62                 return ERR_PTR(-ENOMEM);
  63 
  64         if (!obj->funcs)
  65                 obj->funcs = &drm_gem_shmem_funcs;
  66 
  67         ret = drm_gem_object_init(dev, obj, size);
  68         if (ret)
  69                 goto err_free;
  70 
  71         ret = drm_gem_create_mmap_offset(obj);
  72         if (ret)
  73                 goto err_release;
  74 
  75         shmem = to_drm_gem_shmem_obj(obj);
  76         mutex_init(&shmem->pages_lock);
  77         mutex_init(&shmem->vmap_lock);
  78         INIT_LIST_HEAD(&shmem->madv_list);
  79 
  80         /*
  81          * Our buffers are kept pinned, so allocating them
  82          * from the MOVABLE zone is a really bad idea, and
  83          * conflicts with CMA. See comments above new_inode()
  84          * why this is required _and_ expected if you're
  85          * going to pin these pages.
  86          */
  87         mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
  88                              __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
  89 
  90         return shmem;
  91 
  92 err_release:
  93         drm_gem_object_release(obj);
  94 err_free:
  95         kfree(obj);
  96 
  97         return ERR_PTR(ret);
  98 }
  99 EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
 100 
 101 /**
 102  * drm_gem_shmem_free_object - Free resources associated with a shmem GEM object
 103  * @obj: GEM object to free
 104  *
 105  * This function cleans up the GEM object state and frees the memory used to
 106  * store the object itself.
 107  */
 108 void drm_gem_shmem_free_object(struct drm_gem_object *obj)
 109 {
 110         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 111 
 112         WARN_ON(shmem->vmap_use_count);
 113 
 114         if (obj->import_attach) {
 115                 shmem->pages_use_count--;
 116                 drm_prime_gem_destroy(obj, shmem->sgt);
 117                 kvfree(shmem->pages);
 118         } else {
 119                 if (shmem->sgt) {
 120                         dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl,
 121                                      shmem->sgt->nents, DMA_BIDIRECTIONAL);
 122                         sg_free_table(shmem->sgt);
 123                         kfree(shmem->sgt);
 124                 }
 125                 if (shmem->pages)
 126                         drm_gem_shmem_put_pages(shmem);
 127         }
 128 
 129         WARN_ON(shmem->pages_use_count);
 130 
 131         drm_gem_object_release(obj);
 132         mutex_destroy(&shmem->pages_lock);
 133         mutex_destroy(&shmem->vmap_lock);
 134         kfree(shmem);
 135 }
 136 EXPORT_SYMBOL_GPL(drm_gem_shmem_free_object);
 137 
 138 static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
 139 {
 140         struct drm_gem_object *obj = &shmem->base;
 141         struct page **pages;
 142 
 143         if (shmem->pages_use_count++ > 0)
 144                 return 0;
 145 
 146         pages = drm_gem_get_pages(obj);
 147         if (IS_ERR(pages)) {
 148                 DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
 149                 shmem->pages_use_count = 0;
 150                 return PTR_ERR(pages);
 151         }
 152 
 153         shmem->pages = pages;
 154 
 155         return 0;
 156 }
 157 
 158 /*
 159  * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
 160  * @shmem: shmem GEM object
 161  *
 162  * This function makes sure that backing pages exists for the shmem GEM object
 163  * and increases the use count.
 164  *
 165  * Returns:
 166  * 0 on success or a negative error code on failure.
 167  */
 168 int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
 169 {
 170         int ret;
 171 
 172         ret = mutex_lock_interruptible(&shmem->pages_lock);
 173         if (ret)
 174                 return ret;
 175         ret = drm_gem_shmem_get_pages_locked(shmem);
 176         mutex_unlock(&shmem->pages_lock);
 177 
 178         return ret;
 179 }
 180 EXPORT_SYMBOL(drm_gem_shmem_get_pages);
 181 
 182 static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
 183 {
 184         struct drm_gem_object *obj = &shmem->base;
 185 
 186         if (WARN_ON_ONCE(!shmem->pages_use_count))
 187                 return;
 188 
 189         if (--shmem->pages_use_count > 0)
 190                 return;
 191 
 192         drm_gem_put_pages(obj, shmem->pages,
 193                           shmem->pages_mark_dirty_on_put,
 194                           shmem->pages_mark_accessed_on_put);
 195         shmem->pages = NULL;
 196 }
 197 
 198 /*
 199  * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
 200  * @shmem: shmem GEM object
 201  *
 202  * This function decreases the use count and puts the backing pages when use drops to zero.
 203  */
 204 void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
 205 {
 206         mutex_lock(&shmem->pages_lock);
 207         drm_gem_shmem_put_pages_locked(shmem);
 208         mutex_unlock(&shmem->pages_lock);
 209 }
 210 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
 211 
 212 /**
 213  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
 214  * @obj: GEM object
 215  *
 216  * This function makes sure the backing pages are pinned in memory while the
 217  * buffer is exported.
 218  *
 219  * Returns:
 220  * 0 on success or a negative error code on failure.
 221  */
 222 int drm_gem_shmem_pin(struct drm_gem_object *obj)
 223 {
 224         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 225 
 226         return drm_gem_shmem_get_pages(shmem);
 227 }
 228 EXPORT_SYMBOL(drm_gem_shmem_pin);
 229 
 230 /**
 231  * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
 232  * @obj: GEM object
 233  *
 234  * This function removes the requirement that the backing pages are pinned in
 235  * memory.
 236  */
 237 void drm_gem_shmem_unpin(struct drm_gem_object *obj)
 238 {
 239         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 240 
 241         drm_gem_shmem_put_pages(shmem);
 242 }
 243 EXPORT_SYMBOL(drm_gem_shmem_unpin);
 244 
 245 static void *drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem)
 246 {
 247         struct drm_gem_object *obj = &shmem->base;
 248         int ret;
 249 
 250         if (shmem->vmap_use_count++ > 0)
 251                 return shmem->vaddr;
 252 
 253         ret = drm_gem_shmem_get_pages(shmem);
 254         if (ret)
 255                 goto err_zero_use;
 256 
 257         if (obj->import_attach)
 258                 shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
 259         else
 260                 shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
 261                                     VM_MAP, pgprot_writecombine(PAGE_KERNEL));
 262 
 263         if (!shmem->vaddr) {
 264                 DRM_DEBUG_KMS("Failed to vmap pages\n");
 265                 ret = -ENOMEM;
 266                 goto err_put_pages;
 267         }
 268 
 269         return shmem->vaddr;
 270 
 271 err_put_pages:
 272         drm_gem_shmem_put_pages(shmem);
 273 err_zero_use:
 274         shmem->vmap_use_count = 0;
 275 
 276         return ERR_PTR(ret);
 277 }
 278 
 279 /*
 280  * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
 281  * @shmem: shmem GEM object
 282  *
 283  * This function makes sure that a virtual address exists for the buffer backing
 284  * the shmem GEM object.
 285  *
 286  * Returns:
 287  * 0 on success or a negative error code on failure.
 288  */
 289 void *drm_gem_shmem_vmap(struct drm_gem_object *obj)
 290 {
 291         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 292         void *vaddr;
 293         int ret;
 294 
 295         ret = mutex_lock_interruptible(&shmem->vmap_lock);
 296         if (ret)
 297                 return ERR_PTR(ret);
 298         vaddr = drm_gem_shmem_vmap_locked(shmem);
 299         mutex_unlock(&shmem->vmap_lock);
 300 
 301         return vaddr;
 302 }
 303 EXPORT_SYMBOL(drm_gem_shmem_vmap);
 304 
 305 static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem)
 306 {
 307         struct drm_gem_object *obj = &shmem->base;
 308 
 309         if (WARN_ON_ONCE(!shmem->vmap_use_count))
 310                 return;
 311 
 312         if (--shmem->vmap_use_count > 0)
 313                 return;
 314 
 315         if (obj->import_attach)
 316                 dma_buf_vunmap(obj->import_attach->dmabuf, shmem->vaddr);
 317         else
 318                 vunmap(shmem->vaddr);
 319 
 320         shmem->vaddr = NULL;
 321         drm_gem_shmem_put_pages(shmem);
 322 }
 323 
 324 /*
 325  * drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
 326  * @shmem: shmem GEM object
 327  *
 328  * This function removes the virtual address when use count drops to zero.
 329  */
 330 void drm_gem_shmem_vunmap(struct drm_gem_object *obj, void *vaddr)
 331 {
 332         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 333 
 334         mutex_lock(&shmem->vmap_lock);
 335         drm_gem_shmem_vunmap_locked(shmem);
 336         mutex_unlock(&shmem->vmap_lock);
 337 }
 338 EXPORT_SYMBOL(drm_gem_shmem_vunmap);
 339 
 340 struct drm_gem_shmem_object *
 341 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
 342                                  struct drm_device *dev, size_t size,
 343                                  uint32_t *handle)
 344 {
 345         struct drm_gem_shmem_object *shmem;
 346         int ret;
 347 
 348         shmem = drm_gem_shmem_create(dev, size);
 349         if (IS_ERR(shmem))
 350                 return shmem;
 351 
 352         /*
 353          * Allocate an id of idr table where the obj is registered
 354          * and handle has the id what user can see.
 355          */
 356         ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
 357         /* drop reference from allocate - handle holds it now. */
 358         drm_gem_object_put_unlocked(&shmem->base);
 359         if (ret)
 360                 return ERR_PTR(ret);
 361 
 362         return shmem;
 363 }
 364 EXPORT_SYMBOL(drm_gem_shmem_create_with_handle);
 365 
 366 /* Update madvise status, returns true if not purged, else
 367  * false or -errno.
 368  */
 369 int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv)
 370 {
 371         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 372 
 373         mutex_lock(&shmem->pages_lock);
 374 
 375         if (shmem->madv >= 0)
 376                 shmem->madv = madv;
 377 
 378         madv = shmem->madv;
 379 
 380         mutex_unlock(&shmem->pages_lock);
 381 
 382         return (madv >= 0);
 383 }
 384 EXPORT_SYMBOL(drm_gem_shmem_madvise);
 385 
 386 void drm_gem_shmem_purge_locked(struct drm_gem_object *obj)
 387 {
 388         struct drm_device *dev = obj->dev;
 389         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 390 
 391         WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
 392 
 393         dma_unmap_sg(obj->dev->dev, shmem->sgt->sgl,
 394                      shmem->sgt->nents, DMA_BIDIRECTIONAL);
 395         sg_free_table(shmem->sgt);
 396         kfree(shmem->sgt);
 397         shmem->sgt = NULL;
 398 
 399         drm_gem_shmem_put_pages_locked(shmem);
 400 
 401         shmem->madv = -1;
 402 
 403         drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
 404         drm_gem_free_mmap_offset(obj);
 405 
 406         /* Our goal here is to return as much of the memory as
 407          * is possible back to the system as we are called from OOM.
 408          * To do this we must instruct the shmfs to drop all of its
 409          * backing pages, *now*.
 410          */
 411         shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
 412 
 413         invalidate_mapping_pages(file_inode(obj->filp)->i_mapping,
 414                         0, (loff_t)-1);
 415 }
 416 EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
 417 
 418 bool drm_gem_shmem_purge(struct drm_gem_object *obj)
 419 {
 420         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 421 
 422         if (!mutex_trylock(&shmem->pages_lock))
 423                 return false;
 424         drm_gem_shmem_purge_locked(obj);
 425         mutex_unlock(&shmem->pages_lock);
 426 
 427         return true;
 428 }
 429 EXPORT_SYMBOL(drm_gem_shmem_purge);
 430 
 431 /**
 432  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
 433  * @file: DRM file structure to create the dumb buffer for
 434  * @dev: DRM device
 435  * @args: IOCTL data
 436  *
 437  * This function computes the pitch of the dumb buffer and rounds it up to an
 438  * integer number of bytes per pixel. Drivers for hardware that doesn't have
 439  * any additional restrictions on the pitch can directly use this function as
 440  * their &drm_driver.dumb_create callback.
 441  *
 442  * For hardware with additional restrictions, drivers can adjust the fields
 443  * set up by userspace before calling into this function.
 444  *
 445  * Returns:
 446  * 0 on success or a negative error code on failure.
 447  */
 448 int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
 449                               struct drm_mode_create_dumb *args)
 450 {
 451         u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
 452         struct drm_gem_shmem_object *shmem;
 453 
 454         if (!args->pitch || !args->size) {
 455                 args->pitch = min_pitch;
 456                 args->size = args->pitch * args->height;
 457         } else {
 458                 /* ensure sane minimum values */
 459                 if (args->pitch < min_pitch)
 460                         args->pitch = min_pitch;
 461                 if (args->size < args->pitch * args->height)
 462                         args->size = args->pitch * args->height;
 463         }
 464 
 465         shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
 466 
 467         return PTR_ERR_OR_ZERO(shmem);
 468 }
 469 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
 470 
 471 static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
 472 {
 473         struct vm_area_struct *vma = vmf->vma;
 474         struct drm_gem_object *obj = vma->vm_private_data;
 475         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 476         loff_t num_pages = obj->size >> PAGE_SHIFT;
 477         struct page *page;
 478 
 479         if (vmf->pgoff >= num_pages || WARN_ON_ONCE(!shmem->pages))
 480                 return VM_FAULT_SIGBUS;
 481 
 482         page = shmem->pages[vmf->pgoff];
 483 
 484         return vmf_insert_page(vma, vmf->address, page);
 485 }
 486 
 487 static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 488 {
 489         struct drm_gem_object *obj = vma->vm_private_data;
 490         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 491         int ret;
 492 
 493         ret = drm_gem_shmem_get_pages(shmem);
 494         WARN_ON_ONCE(ret != 0);
 495 
 496         drm_gem_vm_open(vma);
 497 }
 498 
 499 static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
 500 {
 501         struct drm_gem_object *obj = vma->vm_private_data;
 502         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 503 
 504         drm_gem_shmem_put_pages(shmem);
 505         drm_gem_vm_close(vma);
 506 }
 507 
 508 const struct vm_operations_struct drm_gem_shmem_vm_ops = {
 509         .fault = drm_gem_shmem_fault,
 510         .open = drm_gem_shmem_vm_open,
 511         .close = drm_gem_shmem_vm_close,
 512 };
 513 EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
 514 
 515 /**
 516  * drm_gem_shmem_mmap - Memory-map a shmem GEM object
 517  * @filp: File object
 518  * @vma: VMA for the area to be mapped
 519  *
 520  * This function implements an augmented version of the GEM DRM file mmap
 521  * operation for shmem objects. Drivers which employ the shmem helpers should
 522  * use this function as their &file_operations.mmap handler in the DRM device file's
 523  * file_operations structure.
 524  *
 525  * Instead of directly referencing this function, drivers should use the
 526  * DEFINE_DRM_GEM_SHMEM_FOPS() macro.
 527  *
 528  * Returns:
 529  * 0 on success or a negative error code on failure.
 530  */
 531 int drm_gem_shmem_mmap(struct file *filp, struct vm_area_struct *vma)
 532 {
 533         struct drm_gem_shmem_object *shmem;
 534         int ret;
 535 
 536         ret = drm_gem_mmap(filp, vma);
 537         if (ret)
 538                 return ret;
 539 
 540         shmem = to_drm_gem_shmem_obj(vma->vm_private_data);
 541 
 542         ret = drm_gem_shmem_get_pages(shmem);
 543         if (ret) {
 544                 drm_gem_vm_close(vma);
 545                 return ret;
 546         }
 547 
 548         /* VM_PFNMAP was set by drm_gem_mmap() */
 549         vma->vm_flags &= ~VM_PFNMAP;
 550         vma->vm_flags |= VM_MIXEDMAP;
 551 
 552         /* Remove the fake offset */
 553         vma->vm_pgoff -= drm_vma_node_start(&shmem->base.vma_node);
 554 
 555         return 0;
 556 }
 557 EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
 558 
 559 /**
 560  * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
 561  * @p: DRM printer
 562  * @indent: Tab indentation level
 563  * @obj: GEM object
 564  */
 565 void drm_gem_shmem_print_info(struct drm_printer *p, unsigned int indent,
 566                               const struct drm_gem_object *obj)
 567 {
 568         const struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 569 
 570         drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
 571         drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
 572         drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
 573 }
 574 EXPORT_SYMBOL(drm_gem_shmem_print_info);
 575 
 576 /**
 577  * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
 578  *                              pages for a shmem GEM object
 579  * @obj: GEM object
 580  *
 581  * This function exports a scatter/gather table suitable for PRIME usage by
 582  * calling the standard DMA mapping API.
 583  *
 584  * Returns:
 585  * A pointer to the scatter/gather table of pinned pages or NULL on failure.
 586  */
 587 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
 588 {
 589         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 590 
 591         return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT);
 592 }
 593 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
 594 
 595 /**
 596  * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
 597  *                               scatter/gather table for a shmem GEM object.
 598  * @obj: GEM object
 599  *
 600  * This function returns a scatter/gather table suitable for driver usage. If
 601  * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
 602  * table created.
 603  *
 604  * Returns:
 605  * A pointer to the scatter/gather table of pinned pages or errno on failure.
 606  */
 607 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj)
 608 {
 609         int ret;
 610         struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 611         struct sg_table *sgt;
 612 
 613         if (shmem->sgt)
 614                 return shmem->sgt;
 615 
 616         WARN_ON(obj->import_attach);
 617 
 618         ret = drm_gem_shmem_get_pages(shmem);
 619         if (ret)
 620                 return ERR_PTR(ret);
 621 
 622         sgt = drm_gem_shmem_get_sg_table(&shmem->base);
 623         if (IS_ERR(sgt)) {
 624                 ret = PTR_ERR(sgt);
 625                 goto err_put_pages;
 626         }
 627         /* Map the pages for use by the h/w. */
 628         dma_map_sg(obj->dev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL);
 629 
 630         shmem->sgt = sgt;
 631 
 632         return sgt;
 633 
 634 err_put_pages:
 635         drm_gem_shmem_put_pages(shmem);
 636         return ERR_PTR(ret);
 637 }
 638 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);
 639 
 640 /**
 641  * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from
 642  *                 another driver's scatter/gather table of pinned pages
 643  * @dev: Device to import into
 644  * @attach: DMA-BUF attachment
 645  * @sgt: Scatter/gather table of pinned pages
 646  *
 647  * This function imports a scatter/gather table exported via DMA-BUF by
 648  * another driver. Drivers that use the shmem helpers should set this as their
 649  * &drm_driver.gem_prime_import_sg_table callback.
 650  *
 651  * Returns:
 652  * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
 653  * error code on failure.
 654  */
 655 struct drm_gem_object *
 656 drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
 657                                     struct dma_buf_attachment *attach,
 658                                     struct sg_table *sgt)
 659 {
 660         size_t size = PAGE_ALIGN(attach->dmabuf->size);
 661         size_t npages = size >> PAGE_SHIFT;
 662         struct drm_gem_shmem_object *shmem;
 663         int ret;
 664 
 665         shmem = drm_gem_shmem_create(dev, size);
 666         if (IS_ERR(shmem))
 667                 return ERR_CAST(shmem);
 668 
 669         shmem->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
 670         if (!shmem->pages) {
 671                 ret = -ENOMEM;
 672                 goto err_free_gem;
 673         }
 674 
 675         ret = drm_prime_sg_to_page_addr_arrays(sgt, shmem->pages, NULL, npages);
 676         if (ret < 0)
 677                 goto err_free_array;
 678 
 679         shmem->sgt = sgt;
 680         shmem->pages_use_count = 1; /* Permanently pinned from our point of view */
 681 
 682         DRM_DEBUG_PRIME("size = %zu\n", size);
 683 
 684         return &shmem->base;
 685 
 686 err_free_array:
 687         kvfree(shmem->pages);
 688 err_free_gem:
 689         drm_gem_object_put_unlocked(&shmem->base);
 690 
 691         return ERR_PTR(ret);
 692 }
 693 EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);