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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
27static 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 .mmap = drm_gem_shmem_mmap,
36};
37
38static struct drm_gem_shmem_object *
39__drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
40{
41 struct drm_gem_shmem_object *shmem;
42 struct drm_gem_object *obj;
43 int ret = 0;
44
45 size = PAGE_ALIGN(size);
46
47 if (dev->driver->gem_create_object)
48 obj = dev->driver->gem_create_object(dev, size);
49 else
50 obj = kzalloc(sizeof(*shmem), GFP_KERNEL);
51 if (!obj)
52 return ERR_PTR(-ENOMEM);
53
54 shmem = to_drm_gem_shmem_obj(obj);
55
56 if (!obj->funcs)
57 obj->funcs = &drm_gem_shmem_funcs;
58
59 if (private) {
60 drm_gem_private_object_init(dev, obj, size);
61 shmem->map_wc = false; /* dma-buf mappings use always writecombine */
62 } else {
63 ret = drm_gem_object_init(dev, obj, size);
64 }
65 if (ret)
66 goto err_free;
67
68 ret = drm_gem_create_mmap_offset(obj);
69 if (ret)
70 goto err_release;
71
72 mutex_init(&shmem->pages_lock);
73 mutex_init(&shmem->vmap_lock);
74 INIT_LIST_HEAD(&shmem->madv_list);
75
76 if (!private) {
77 /*
78 * Our buffers are kept pinned, so allocating them
79 * from the MOVABLE zone is a really bad idea, and
80 * conflicts with CMA. See comments above new_inode()
81 * why this is required _and_ expected if you're
82 * going to pin these pages.
83 */
84 mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
85 __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
86 }
87
88 return shmem;
89
90err_release:
91 drm_gem_object_release(obj);
92err_free:
93 kfree(obj);
94
95 return ERR_PTR(ret);
96}
97/**
98 * drm_gem_shmem_create - Allocate an object with the given size
99 * @dev: DRM device
100 * @size: Size of the object to allocate
101 *
102 * This function creates a shmem GEM object.
103 *
104 * Returns:
105 * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
106 * error code on failure.
107 */
108struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
109{
110 return __drm_gem_shmem_create(dev, size, false);
111}
112EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
113
114/**
115 * drm_gem_shmem_free_object - Free resources associated with a shmem GEM object
116 * @obj: GEM object to free
117 *
118 * This function cleans up the GEM object state and frees the memory used to
119 * store the object itself. It should be used to implement
120 * &drm_gem_object_funcs.free.
121 */
122void drm_gem_shmem_free_object(struct drm_gem_object *obj)
123{
124 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
125
126 WARN_ON(shmem->vmap_use_count);
127
128 if (obj->import_attach) {
129 drm_prime_gem_destroy(obj, shmem->sgt);
130 } else {
131 if (shmem->sgt) {
132 dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
133 DMA_BIDIRECTIONAL, 0);
134 sg_free_table(shmem->sgt);
135 kfree(shmem->sgt);
136 }
137 if (shmem->pages)
138 drm_gem_shmem_put_pages(shmem);
139 }
140
141 WARN_ON(shmem->pages_use_count);
142
143 drm_gem_object_release(obj);
144 mutex_destroy(&shmem->pages_lock);
145 mutex_destroy(&shmem->vmap_lock);
146 kfree(shmem);
147}
148EXPORT_SYMBOL_GPL(drm_gem_shmem_free_object);
149
150static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
151{
152 struct drm_gem_object *obj = &shmem->base;
153 struct page **pages;
154
155 if (shmem->pages_use_count++ > 0)
156 return 0;
157
158 pages = drm_gem_get_pages(obj);
159 if (IS_ERR(pages)) {
160 DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
161 shmem->pages_use_count = 0;
162 return PTR_ERR(pages);
163 }
164
165 shmem->pages = pages;
166
167 return 0;
168}
169
170/*
171 * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
172 * @shmem: shmem GEM object
173 *
174 * This function makes sure that backing pages exists for the shmem GEM object
175 * and increases the use count.
176 *
177 * Returns:
178 * 0 on success or a negative error code on failure.
179 */
180int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
181{
182 int ret;
183
184 WARN_ON(shmem->base.import_attach);
185
186 ret = mutex_lock_interruptible(&shmem->pages_lock);
187 if (ret)
188 return ret;
189 ret = drm_gem_shmem_get_pages_locked(shmem);
190 mutex_unlock(&shmem->pages_lock);
191
192 return ret;
193}
194EXPORT_SYMBOL(drm_gem_shmem_get_pages);
195
196static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
197{
198 struct drm_gem_object *obj = &shmem->base;
199
200 if (WARN_ON_ONCE(!shmem->pages_use_count))
201 return;
202
203 if (--shmem->pages_use_count > 0)
204 return;
205
206 drm_gem_put_pages(obj, shmem->pages,
207 shmem->pages_mark_dirty_on_put,
208 shmem->pages_mark_accessed_on_put);
209 shmem->pages = NULL;
210}
211
212/*
213 * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
214 * @shmem: shmem GEM object
215 *
216 * This function decreases the use count and puts the backing pages when use drops to zero.
217 */
218void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
219{
220 mutex_lock(&shmem->pages_lock);
221 drm_gem_shmem_put_pages_locked(shmem);
222 mutex_unlock(&shmem->pages_lock);
223}
224EXPORT_SYMBOL(drm_gem_shmem_put_pages);
225
226/**
227 * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
228 * @obj: GEM object
229 *
230 * This function makes sure the backing pages are pinned in memory while the
231 * buffer is exported. It should only be used to implement
232 * &drm_gem_object_funcs.pin.
233 *
234 * Returns:
235 * 0 on success or a negative error code on failure.
236 */
237int drm_gem_shmem_pin(struct drm_gem_object *obj)
238{
239 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
240
241 WARN_ON(shmem->base.import_attach);
242
243 return drm_gem_shmem_get_pages(shmem);
244}
245EXPORT_SYMBOL(drm_gem_shmem_pin);
246
247/**
248 * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
249 * @obj: GEM object
250 *
251 * This function removes the requirement that the backing pages are pinned in
252 * memory. It should only be used to implement &drm_gem_object_funcs.unpin.
253 */
254void drm_gem_shmem_unpin(struct drm_gem_object *obj)
255{
256 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
257
258 WARN_ON(shmem->base.import_attach);
259
260 drm_gem_shmem_put_pages(shmem);
261}
262EXPORT_SYMBOL(drm_gem_shmem_unpin);
263
264static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map)
265{
266 struct drm_gem_object *obj = &shmem->base;
267 int ret = 0;
268
269 if (shmem->vmap_use_count++ > 0) {
270 dma_buf_map_set_vaddr(map, shmem->vaddr);
271 return 0;
272 }
273
274 if (obj->import_attach) {
275 ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
276 if (!ret) {
277 if (WARN_ON(map->is_iomem)) {
278 ret = -EIO;
279 goto err_put_pages;
280 }
281 shmem->vaddr = map->vaddr;
282 }
283 } else {
284 pgprot_t prot = PAGE_KERNEL;
285
286 ret = drm_gem_shmem_get_pages(shmem);
287 if (ret)
288 goto err_zero_use;
289
290 if (shmem->map_wc)
291 prot = pgprot_writecombine(prot);
292 shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
293 VM_MAP, prot);
294 if (!shmem->vaddr)
295 ret = -ENOMEM;
296 else
297 dma_buf_map_set_vaddr(map, shmem->vaddr);
298 }
299
300 if (ret) {
301 DRM_DEBUG_KMS("Failed to vmap pages, error %d\n", ret);
302 goto err_put_pages;
303 }
304
305 return 0;
306
307err_put_pages:
308 if (!obj->import_attach)
309 drm_gem_shmem_put_pages(shmem);
310err_zero_use:
311 shmem->vmap_use_count = 0;
312
313 return ret;
314}
315
316/*
317 * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
318 * @shmem: shmem GEM object
319 * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
320 * store.
321 *
322 * This function makes sure that a contiguous kernel virtual address mapping
323 * exists for the buffer backing the shmem GEM object.
324 *
325 * This function can be used to implement &drm_gem_object_funcs.vmap. But it can
326 * also be called by drivers directly, in which case it will hide the
327 * differences between dma-buf imported and natively allocated objects.
328 *
329 * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap().
330 *
331 * Returns:
332 * 0 on success or a negative error code on failure.
333 */
334int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map)
335{
336 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
337 int ret;
338
339 ret = mutex_lock_interruptible(&shmem->vmap_lock);
340 if (ret)
341 return ret;
342 ret = drm_gem_shmem_vmap_locked(shmem, map);
343 mutex_unlock(&shmem->vmap_lock);
344
345 return ret;
346}
347EXPORT_SYMBOL(drm_gem_shmem_vmap);
348
349static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
350 struct dma_buf_map *map)
351{
352 struct drm_gem_object *obj = &shmem->base;
353
354 if (WARN_ON_ONCE(!shmem->vmap_use_count))
355 return;
356
357 if (--shmem->vmap_use_count > 0)
358 return;
359
360 if (obj->import_attach) {
361 dma_buf_vunmap(obj->import_attach->dmabuf, map);
362 } else {
363 vunmap(shmem->vaddr);
364 drm_gem_shmem_put_pages(shmem);
365 }
366
367 shmem->vaddr = NULL;
368}
369
370/*
371 * drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
372 * @shmem: shmem GEM object
373 * @map: Kernel virtual address where the SHMEM GEM object was mapped
374 *
375 * This function cleans up a kernel virtual address mapping acquired by
376 * drm_gem_shmem_vmap(). The mapping is only removed when the use count drops to
377 * zero.
378 *
379 * This function can be used to implement &drm_gem_object_funcs.vmap. But it can
380 * also be called by drivers directly, in which case it will hide the
381 * differences between dma-buf imported and natively allocated objects.
382 */
383void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map)
384{
385 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
386
387 mutex_lock(&shmem->vmap_lock);
388 drm_gem_shmem_vunmap_locked(shmem, map);
389 mutex_unlock(&shmem->vmap_lock);
390}
391EXPORT_SYMBOL(drm_gem_shmem_vunmap);
392
393struct drm_gem_shmem_object *
394drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
395 struct drm_device *dev, size_t size,
396 uint32_t *handle)
397{
398 struct drm_gem_shmem_object *shmem;
399 int ret;
400
401 shmem = drm_gem_shmem_create(dev, size);
402 if (IS_ERR(shmem))
403 return shmem;
404
405 /*
406 * Allocate an id of idr table where the obj is registered
407 * and handle has the id what user can see.
408 */
409 ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
410 /* drop reference from allocate - handle holds it now. */
411 drm_gem_object_put(&shmem->base);
412 if (ret)
413 return ERR_PTR(ret);
414
415 return shmem;
416}
417EXPORT_SYMBOL(drm_gem_shmem_create_with_handle);
418
419/* Update madvise status, returns true if not purged, else
420 * false or -errno.
421 */
422int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv)
423{
424 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
425
426 mutex_lock(&shmem->pages_lock);
427
428 if (shmem->madv >= 0)
429 shmem->madv = madv;
430
431 madv = shmem->madv;
432
433 mutex_unlock(&shmem->pages_lock);
434
435 return (madv >= 0);
436}
437EXPORT_SYMBOL(drm_gem_shmem_madvise);
438
439void drm_gem_shmem_purge_locked(struct drm_gem_object *obj)
440{
441 struct drm_device *dev = obj->dev;
442 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
443
444 WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
445
446 dma_unmap_sgtable(obj->dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
447 sg_free_table(shmem->sgt);
448 kfree(shmem->sgt);
449 shmem->sgt = NULL;
450
451 drm_gem_shmem_put_pages_locked(shmem);
452
453 shmem->madv = -1;
454
455 drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
456 drm_gem_free_mmap_offset(obj);
457
458 /* Our goal here is to return as much of the memory as
459 * is possible back to the system as we are called from OOM.
460 * To do this we must instruct the shmfs to drop all of its
461 * backing pages, *now*.
462 */
463 shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
464
465 invalidate_mapping_pages(file_inode(obj->filp)->i_mapping,
466 0, (loff_t)-1);
467}
468EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
469
470bool drm_gem_shmem_purge(struct drm_gem_object *obj)
471{
472 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
473
474 if (!mutex_trylock(&shmem->pages_lock))
475 return false;
476 drm_gem_shmem_purge_locked(obj);
477 mutex_unlock(&shmem->pages_lock);
478
479 return true;
480}
481EXPORT_SYMBOL(drm_gem_shmem_purge);
482
483/**
484 * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
485 * @file: DRM file structure to create the dumb buffer for
486 * @dev: DRM device
487 * @args: IOCTL data
488 *
489 * This function computes the pitch of the dumb buffer and rounds it up to an
490 * integer number of bytes per pixel. Drivers for hardware that doesn't have
491 * any additional restrictions on the pitch can directly use this function as
492 * their &drm_driver.dumb_create callback.
493 *
494 * For hardware with additional restrictions, drivers can adjust the fields
495 * set up by userspace before calling into this function.
496 *
497 * Returns:
498 * 0 on success or a negative error code on failure.
499 */
500int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
501 struct drm_mode_create_dumb *args)
502{
503 u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
504 struct drm_gem_shmem_object *shmem;
505
506 if (!args->pitch || !args->size) {
507 args->pitch = min_pitch;
508 args->size = args->pitch * args->height;
509 } else {
510 /* ensure sane minimum values */
511 if (args->pitch < min_pitch)
512 args->pitch = min_pitch;
513 if (args->size < args->pitch * args->height)
514 args->size = args->pitch * args->height;
515 }
516
517 shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
518
519 return PTR_ERR_OR_ZERO(shmem);
520}
521EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
522
523static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
524{
525 struct vm_area_struct *vma = vmf->vma;
526 struct drm_gem_object *obj = vma->vm_private_data;
527 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
528 loff_t num_pages = obj->size >> PAGE_SHIFT;
529 vm_fault_t ret;
530 struct page *page;
531 pgoff_t page_offset;
532
533 /* We don't use vmf->pgoff since that has the fake offset */
534 page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
535
536 mutex_lock(&shmem->pages_lock);
537
538 if (page_offset >= num_pages ||
539 WARN_ON_ONCE(!shmem->pages) ||
540 shmem->madv < 0) {
541 ret = VM_FAULT_SIGBUS;
542 } else {
543 page = shmem->pages[page_offset];
544
545 ret = vmf_insert_page(vma, vmf->address, page);
546 }
547
548 mutex_unlock(&shmem->pages_lock);
549
550 return ret;
551}
552
553static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
554{
555 struct drm_gem_object *obj = vma->vm_private_data;
556 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
557 int ret;
558
559 WARN_ON(shmem->base.import_attach);
560
561 ret = drm_gem_shmem_get_pages(shmem);
562 WARN_ON_ONCE(ret != 0);
563
564 drm_gem_vm_open(vma);
565}
566
567static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
568{
569 struct drm_gem_object *obj = vma->vm_private_data;
570 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
571
572 drm_gem_shmem_put_pages(shmem);
573 drm_gem_vm_close(vma);
574}
575
576static const struct vm_operations_struct drm_gem_shmem_vm_ops = {
577 .fault = drm_gem_shmem_fault,
578 .open = drm_gem_shmem_vm_open,
579 .close = drm_gem_shmem_vm_close,
580};
581
582/**
583 * drm_gem_shmem_mmap - Memory-map a shmem GEM object
584 * @obj: gem object
585 * @vma: VMA for the area to be mapped
586 *
587 * This function implements an augmented version of the GEM DRM file mmap
588 * operation for shmem objects. Drivers which employ the shmem helpers should
589 * use this function as their &drm_gem_object_funcs.mmap handler.
590 *
591 * Returns:
592 * 0 on success or a negative error code on failure.
593 */
594int drm_gem_shmem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
595{
596 struct drm_gem_shmem_object *shmem;
597 int ret;
598
599 if (obj->import_attach) {
600 /* Drop the reference drm_gem_mmap_obj() acquired.*/
601 drm_gem_object_put(obj);
602 vma->vm_private_data = NULL;
603
604 return dma_buf_mmap(obj->dma_buf, vma, 0);
605 }
606
607 shmem = to_drm_gem_shmem_obj(obj);
608
609 ret = drm_gem_shmem_get_pages(shmem);
610 if (ret) {
611 drm_gem_vm_close(vma);
612 return ret;
613 }
614
615 vma->vm_flags |= VM_MIXEDMAP | VM_DONTEXPAND;
616 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
617 if (shmem->map_wc)
618 vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
619 vma->vm_ops = &drm_gem_shmem_vm_ops;
620
621 return 0;
622}
623EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
624
625/**
626 * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
627 * @p: DRM printer
628 * @indent: Tab indentation level
629 * @obj: GEM object
630 *
631 * This implements the &drm_gem_object_funcs.info callback.
632 */
633void drm_gem_shmem_print_info(struct drm_printer *p, unsigned int indent,
634 const struct drm_gem_object *obj)
635{
636 const struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
637
638 drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
639 drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
640 drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
641}
642EXPORT_SYMBOL(drm_gem_shmem_print_info);
643
644/**
645 * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
646 * pages for a shmem GEM object
647 * @obj: GEM object
648 *
649 * This function exports a scatter/gather table suitable for PRIME usage by
650 * calling the standard DMA mapping API. Drivers should not call this function
651 * directly, instead it should only be used as an implementation for
652 * &drm_gem_object_funcs.get_sg_table.
653 *
654 * Drivers who need to acquire an scatter/gather table for objects need to call
655 * drm_gem_shmem_get_pages_sgt() instead.
656 *
657 * Returns:
658 * A pointer to the scatter/gather table of pinned pages or NULL on failure.
659 */
660struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
661{
662 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
663
664 WARN_ON(shmem->base.import_attach);
665
666 return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SHIFT);
667}
668EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
669
670/**
671 * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
672 * scatter/gather table for a shmem GEM object.
673 * @obj: GEM object
674 *
675 * This function returns a scatter/gather table suitable for driver usage. If
676 * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
677 * table created.
678 *
679 * This is the main function for drivers to get at backing storage, and it hides
680 * and difference between dma-buf imported and natively allocated objects.
681 * drm_gem_shmem_get_sg_table() should not be directly called by drivers.
682 *
683 * Returns:
684 * A pointer to the scatter/gather table of pinned pages or errno on failure.
685 */
686struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj)
687{
688 int ret;
689 struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
690 struct sg_table *sgt;
691
692 if (shmem->sgt)
693 return shmem->sgt;
694
695 WARN_ON(obj->import_attach);
696
697 ret = drm_gem_shmem_get_pages(shmem);
698 if (ret)
699 return ERR_PTR(ret);
700
701 sgt = drm_gem_shmem_get_sg_table(&shmem->base);
702 if (IS_ERR(sgt)) {
703 ret = PTR_ERR(sgt);
704 goto err_put_pages;
705 }
706 /* Map the pages for use by the h/w. */
707 ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
708 if (ret)
709 goto err_free_sgt;
710
711 shmem->sgt = sgt;
712
713 return sgt;
714
715err_free_sgt:
716 sg_free_table(sgt);
717 kfree(sgt);
718err_put_pages:
719 drm_gem_shmem_put_pages(shmem);
720 return ERR_PTR(ret);
721}
722EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);
723
724/**
725 * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from
726 * another driver's scatter/gather table of pinned pages
727 * @dev: Device to import into
728 * @attach: DMA-BUF attachment
729 * @sgt: Scatter/gather table of pinned pages
730 *
731 * This function imports a scatter/gather table exported via DMA-BUF by
732 * another driver. Drivers that use the shmem helpers should set this as their
733 * &drm_driver.gem_prime_import_sg_table callback.
734 *
735 * Returns:
736 * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
737 * error code on failure.
738 */
739struct drm_gem_object *
740drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
741 struct dma_buf_attachment *attach,
742 struct sg_table *sgt)
743{
744 size_t size = PAGE_ALIGN(attach->dmabuf->size);
745 struct drm_gem_shmem_object *shmem;
746
747 shmem = __drm_gem_shmem_create(dev, size, true);
748 if (IS_ERR(shmem))
749 return ERR_CAST(shmem);
750
751 shmem->sgt = sgt;
752
753 DRM_DEBUG_PRIME("size = %zu\n", size);
754
755 return &shmem->base;
756}
757EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);