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/module.h>
9 #include <linux/mutex.h>
10 #include <linux/shmem_fs.h>
11 #include <linux/slab.h>
12 #include <linux/vmalloc.h>
13 #include <linux/module.h>
14 
15 #ifdef CONFIG_X86
16 #include <asm/set_memory.h>
17 #endif
18 
19 #include <drm/drm.h>
20 #include <drm/drm_device.h>
21 #include <drm/drm_drv.h>
22 #include <drm/drm_gem_shmem_helper.h>
23 #include <drm/drm_prime.h>
24 #include <drm/drm_print.h>
25 
26 MODULE_IMPORT_NS(DMA_BUF);
27 
28 /**
29  * DOC: overview
30  *
31  * This library provides helpers for GEM objects backed by shmem buffers
32  * allocated using anonymous pageable memory.
33  *
34  * Functions that operate on the GEM object receive struct &drm_gem_shmem_object.
35  * For GEM callback helpers in struct &drm_gem_object functions, see likewise
36  * named functions with an _object_ infix (e.g., drm_gem_shmem_object_vmap() wraps
37  * drm_gem_shmem_vmap()). These helpers perform the necessary type conversion.
38  */
39 
40 static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
41 	.free = drm_gem_shmem_object_free,
42 	.print_info = drm_gem_shmem_object_print_info,
43 	.pin = drm_gem_shmem_object_pin,
44 	.unpin = drm_gem_shmem_object_unpin,
45 	.get_sg_table = drm_gem_shmem_object_get_sg_table,
46 	.vmap = drm_gem_shmem_object_vmap,
47 	.vunmap = drm_gem_shmem_object_vunmap,
48 	.mmap = drm_gem_shmem_object_mmap,
49 	.vm_ops = &drm_gem_shmem_vm_ops,
50 };
51 
52 static struct drm_gem_shmem_object *
53 __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
54 {
55 	struct drm_gem_shmem_object *shmem;
56 	struct drm_gem_object *obj;
57 	int ret = 0;
58 
59 	size = PAGE_ALIGN(size);
60 
61 	if (dev->driver->gem_create_object) {
62 		obj = dev->driver->gem_create_object(dev, size);
63 		if (IS_ERR(obj))
64 			return ERR_CAST(obj);
65 		shmem = to_drm_gem_shmem_obj(obj);
66 	} else {
67 		shmem = kzalloc(sizeof(*shmem), GFP_KERNEL);
68 		if (!shmem)
69 			return ERR_PTR(-ENOMEM);
70 		obj = &shmem->base;
71 	}
72 
73 	if (!obj->funcs)
74 		obj->funcs = &drm_gem_shmem_funcs;
75 
76 	if (private) {
77 		drm_gem_private_object_init(dev, obj, size);
78 		shmem->map_wc = false; /* dma-buf mappings use always writecombine */
79 	} else {
80 		ret = drm_gem_object_init(dev, obj, size);
81 	}
82 	if (ret)
83 		goto err_free;
84 
85 	ret = drm_gem_create_mmap_offset(obj);
86 	if (ret)
87 		goto err_release;
88 
89 	mutex_init(&shmem->pages_lock);
90 	mutex_init(&shmem->vmap_lock);
91 	INIT_LIST_HEAD(&shmem->madv_list);
92 
93 	if (!private) {
94 		/*
95 		 * Our buffers are kept pinned, so allocating them
96 		 * from the MOVABLE zone is a really bad idea, and
97 		 * conflicts with CMA. See comments above new_inode()
98 		 * why this is required _and_ expected if you're
99 		 * going to pin these pages.
100 		 */
101 		mapping_set_gfp_mask(obj->filp->f_mapping, GFP_HIGHUSER |
102 				     __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
103 	}
104 
105 	return shmem;
106 
107 err_release:
108 	drm_gem_object_release(obj);
109 err_free:
110 	kfree(obj);
111 
112 	return ERR_PTR(ret);
113 }
114 /**
115  * drm_gem_shmem_create - Allocate an object with the given size
116  * @dev: DRM device
117  * @size: Size of the object to allocate
118  *
119  * This function creates a shmem GEM object.
120  *
121  * Returns:
122  * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
123  * error code on failure.
124  */
125 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
126 {
127 	return __drm_gem_shmem_create(dev, size, false);
128 }
129 EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
130 
131 /**
132  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
133  * @shmem: shmem GEM object to free
134  *
135  * This function cleans up the GEM object state and frees the memory used to
136  * store the object itself.
137  */
138 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
139 {
140 	struct drm_gem_object *obj = &shmem->base;
141 
142 	WARN_ON(shmem->vmap_use_count);
143 
144 	if (obj->import_attach) {
145 		drm_prime_gem_destroy(obj, shmem->sgt);
146 	} else {
147 		if (shmem->sgt) {
148 			dma_unmap_sgtable(obj->dev->dev, shmem->sgt,
149 					  DMA_BIDIRECTIONAL, 0);
150 			sg_free_table(shmem->sgt);
151 			kfree(shmem->sgt);
152 		}
153 		if (shmem->pages)
154 			drm_gem_shmem_put_pages(shmem);
155 	}
156 
157 	WARN_ON(shmem->pages_use_count);
158 
159 	drm_gem_object_release(obj);
160 	mutex_destroy(&shmem->pages_lock);
161 	mutex_destroy(&shmem->vmap_lock);
162 	kfree(shmem);
163 }
164 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);
165 
166 static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
167 {
168 	struct drm_gem_object *obj = &shmem->base;
169 	struct page **pages;
170 
171 	if (shmem->pages_use_count++ > 0)
172 		return 0;
173 
174 	pages = drm_gem_get_pages(obj);
175 	if (IS_ERR(pages)) {
176 		DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
177 		shmem->pages_use_count = 0;
178 		return PTR_ERR(pages);
179 	}
180 
181 	/*
182 	 * TODO: Allocating WC pages which are correctly flushed is only
183 	 * supported on x86. Ideal solution would be a GFP_WC flag, which also
184 	 * ttm_pool.c could use.
185 	 */
186 #ifdef CONFIG_X86
187 	if (shmem->map_wc)
188 		set_pages_array_wc(pages, obj->size >> PAGE_SHIFT);
189 #endif
190 
191 	shmem->pages = pages;
192 
193 	return 0;
194 }
195 
196 /*
197  * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
198  * @shmem: shmem GEM object
199  *
200  * This function makes sure that backing pages exists for the shmem GEM object
201  * and increases the use count.
202  *
203  * Returns:
204  * 0 on success or a negative error code on failure.
205  */
206 int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
207 {
208 	int ret;
209 
210 	WARN_ON(shmem->base.import_attach);
211 
212 	ret = mutex_lock_interruptible(&shmem->pages_lock);
213 	if (ret)
214 		return ret;
215 	ret = drm_gem_shmem_get_pages_locked(shmem);
216 	mutex_unlock(&shmem->pages_lock);
217 
218 	return ret;
219 }
220 EXPORT_SYMBOL(drm_gem_shmem_get_pages);
221 
222 static void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
223 {
224 	struct drm_gem_object *obj = &shmem->base;
225 
226 	if (WARN_ON_ONCE(!shmem->pages_use_count))
227 		return;
228 
229 	if (--shmem->pages_use_count > 0)
230 		return;
231 
232 #ifdef CONFIG_X86
233 	if (shmem->map_wc)
234 		set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT);
235 #endif
236 
237 	drm_gem_put_pages(obj, shmem->pages,
238 			  shmem->pages_mark_dirty_on_put,
239 			  shmem->pages_mark_accessed_on_put);
240 	shmem->pages = NULL;
241 }
242 
243 /*
244  * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
245  * @shmem: shmem GEM object
246  *
247  * This function decreases the use count and puts the backing pages when use drops to zero.
248  */
249 void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
250 {
251 	mutex_lock(&shmem->pages_lock);
252 	drm_gem_shmem_put_pages_locked(shmem);
253 	mutex_unlock(&shmem->pages_lock);
254 }
255 EXPORT_SYMBOL(drm_gem_shmem_put_pages);
256 
257 /**
258  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
259  * @shmem: shmem GEM object
260  *
261  * This function makes sure the backing pages are pinned in memory while the
262  * buffer is exported.
263  *
264  * Returns:
265  * 0 on success or a negative error code on failure.
266  */
267 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
268 {
269 	WARN_ON(shmem->base.import_attach);
270 
271 	return drm_gem_shmem_get_pages(shmem);
272 }
273 EXPORT_SYMBOL(drm_gem_shmem_pin);
274 
275 /**
276  * drm_gem_shmem_unpin - Unpin backing pages for a shmem GEM object
277  * @shmem: shmem GEM object
278  *
279  * This function removes the requirement that the backing pages are pinned in
280  * memory.
281  */
282 void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem)
283 {
284 	WARN_ON(shmem->base.import_attach);
285 
286 	drm_gem_shmem_put_pages(shmem);
287 }
288 EXPORT_SYMBOL(drm_gem_shmem_unpin);
289 
290 static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
291 				     struct iosys_map *map)
292 {
293 	struct drm_gem_object *obj = &shmem->base;
294 	int ret = 0;
295 
296 	if (shmem->vmap_use_count++ > 0) {
297 		iosys_map_set_vaddr(map, shmem->vaddr);
298 		return 0;
299 	}
300 
301 	if (obj->import_attach) {
302 		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
303 		if (!ret) {
304 			if (WARN_ON(map->is_iomem)) {
305 				dma_buf_vunmap(obj->import_attach->dmabuf, map);
306 				ret = -EIO;
307 				goto err_put_pages;
308 			}
309 			shmem->vaddr = map->vaddr;
310 		}
311 	} else {
312 		pgprot_t prot = PAGE_KERNEL;
313 
314 		ret = drm_gem_shmem_get_pages(shmem);
315 		if (ret)
316 			goto err_zero_use;
317 
318 		if (shmem->map_wc)
319 			prot = pgprot_writecombine(prot);
320 		shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT,
321 				    VM_MAP, prot);
322 		if (!shmem->vaddr)
323 			ret = -ENOMEM;
324 		else
325 			iosys_map_set_vaddr(map, shmem->vaddr);
326 	}
327 
328 	if (ret) {
329 		DRM_DEBUG_KMS("Failed to vmap pages, error %d\n", ret);
330 		goto err_put_pages;
331 	}
332 
333 	return 0;
334 
335 err_put_pages:
336 	if (!obj->import_attach)
337 		drm_gem_shmem_put_pages(shmem);
338 err_zero_use:
339 	shmem->vmap_use_count = 0;
340 
341 	return ret;
342 }
343 
344 /*
345  * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
346  * @shmem: shmem GEM object
347  * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
348  *       store.
349  *
350  * This function makes sure that a contiguous kernel virtual address mapping
351  * exists for the buffer backing the shmem GEM object. It hides the differences
352  * between dma-buf imported and natively allocated objects.
353  *
354  * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap().
355  *
356  * Returns:
357  * 0 on success or a negative error code on failure.
358  */
359 int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
360 		       struct iosys_map *map)
361 {
362 	int ret;
363 
364 	ret = mutex_lock_interruptible(&shmem->vmap_lock);
365 	if (ret)
366 		return ret;
367 	ret = drm_gem_shmem_vmap_locked(shmem, map);
368 	mutex_unlock(&shmem->vmap_lock);
369 
370 	return ret;
371 }
372 EXPORT_SYMBOL(drm_gem_shmem_vmap);
373 
374 static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
375 					struct iosys_map *map)
376 {
377 	struct drm_gem_object *obj = &shmem->base;
378 
379 	if (WARN_ON_ONCE(!shmem->vmap_use_count))
380 		return;
381 
382 	if (--shmem->vmap_use_count > 0)
383 		return;
384 
385 	if (obj->import_attach) {
386 		dma_buf_vunmap(obj->import_attach->dmabuf, map);
387 	} else {
388 		vunmap(shmem->vaddr);
389 		drm_gem_shmem_put_pages(shmem);
390 	}
391 
392 	shmem->vaddr = NULL;
393 }
394 
395 /*
396  * drm_gem_shmem_vunmap - Unmap a virtual mapping for a shmem GEM object
397  * @shmem: shmem GEM object
398  * @map: Kernel virtual address where the SHMEM GEM object was mapped
399  *
400  * This function cleans up a kernel virtual address mapping acquired by
401  * drm_gem_shmem_vmap(). The mapping is only removed when the use count drops to
402  * zero.
403  *
404  * This function hides the differences between dma-buf imported and natively
405  * allocated objects.
406  */
407 void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
408 			  struct iosys_map *map)
409 {
410 	mutex_lock(&shmem->vmap_lock);
411 	drm_gem_shmem_vunmap_locked(shmem, map);
412 	mutex_unlock(&shmem->vmap_lock);
413 }
414 EXPORT_SYMBOL(drm_gem_shmem_vunmap);
415 
416 static struct drm_gem_shmem_object *
417 drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
418 				 struct drm_device *dev, size_t size,
419 				 uint32_t *handle)
420 {
421 	struct drm_gem_shmem_object *shmem;
422 	int ret;
423 
424 	shmem = drm_gem_shmem_create(dev, size);
425 	if (IS_ERR(shmem))
426 		return shmem;
427 
428 	/*
429 	 * Allocate an id of idr table where the obj is registered
430 	 * and handle has the id what user can see.
431 	 */
432 	ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
433 	/* drop reference from allocate - handle holds it now. */
434 	drm_gem_object_put(&shmem->base);
435 	if (ret)
436 		return ERR_PTR(ret);
437 
438 	return shmem;
439 }
440 
441 /* Update madvise status, returns true if not purged, else
442  * false or -errno.
443  */
444 int drm_gem_shmem_madvise(struct drm_gem_shmem_object *shmem, int madv)
445 {
446 	mutex_lock(&shmem->pages_lock);
447 
448 	if (shmem->madv >= 0)
449 		shmem->madv = madv;
450 
451 	madv = shmem->madv;
452 
453 	mutex_unlock(&shmem->pages_lock);
454 
455 	return (madv >= 0);
456 }
457 EXPORT_SYMBOL(drm_gem_shmem_madvise);
458 
459 void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem)
460 {
461 	struct drm_gem_object *obj = &shmem->base;
462 	struct drm_device *dev = obj->dev;
463 
464 	WARN_ON(!drm_gem_shmem_is_purgeable(shmem));
465 
466 	dma_unmap_sgtable(dev->dev, shmem->sgt, DMA_BIDIRECTIONAL, 0);
467 	sg_free_table(shmem->sgt);
468 	kfree(shmem->sgt);
469 	shmem->sgt = NULL;
470 
471 	drm_gem_shmem_put_pages_locked(shmem);
472 
473 	shmem->madv = -1;
474 
475 	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
476 	drm_gem_free_mmap_offset(obj);
477 
478 	/* Our goal here is to return as much of the memory as
479 	 * is possible back to the system as we are called from OOM.
480 	 * To do this we must instruct the shmfs to drop all of its
481 	 * backing pages, *now*.
482 	 */
483 	shmem_truncate_range(file_inode(obj->filp), 0, (loff_t)-1);
484 
485 	invalidate_mapping_pages(file_inode(obj->filp)->i_mapping, 0, (loff_t)-1);
486 }
487 EXPORT_SYMBOL(drm_gem_shmem_purge_locked);
488 
489 bool drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem)
490 {
491 	if (!mutex_trylock(&shmem->pages_lock))
492 		return false;
493 	drm_gem_shmem_purge_locked(shmem);
494 	mutex_unlock(&shmem->pages_lock);
495 
496 	return true;
497 }
498 EXPORT_SYMBOL(drm_gem_shmem_purge);
499 
500 /**
501  * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
502  * @file: DRM file structure to create the dumb buffer for
503  * @dev: DRM device
504  * @args: IOCTL data
505  *
506  * This function computes the pitch of the dumb buffer and rounds it up to an
507  * integer number of bytes per pixel. Drivers for hardware that doesn't have
508  * any additional restrictions on the pitch can directly use this function as
509  * their &drm_driver.dumb_create callback.
510  *
511  * For hardware with additional restrictions, drivers can adjust the fields
512  * set up by userspace before calling into this function.
513  *
514  * Returns:
515  * 0 on success or a negative error code on failure.
516  */
517 int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
518 			      struct drm_mode_create_dumb *args)
519 {
520 	u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
521 	struct drm_gem_shmem_object *shmem;
522 
523 	if (!args->pitch || !args->size) {
524 		args->pitch = min_pitch;
525 		args->size = PAGE_ALIGN(args->pitch * args->height);
526 	} else {
527 		/* ensure sane minimum values */
528 		if (args->pitch < min_pitch)
529 			args->pitch = min_pitch;
530 		if (args->size < args->pitch * args->height)
531 			args->size = PAGE_ALIGN(args->pitch * args->height);
532 	}
533 
534 	shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
535 
536 	return PTR_ERR_OR_ZERO(shmem);
537 }
538 EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
539 
540 static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
541 {
542 	struct vm_area_struct *vma = vmf->vma;
543 	struct drm_gem_object *obj = vma->vm_private_data;
544 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
545 	loff_t num_pages = obj->size >> PAGE_SHIFT;
546 	vm_fault_t ret;
547 	struct page *page;
548 	pgoff_t page_offset;
549 
550 	/* We don't use vmf->pgoff since that has the fake offset */
551 	page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
552 
553 	mutex_lock(&shmem->pages_lock);
554 
555 	if (page_offset >= num_pages ||
556 	    WARN_ON_ONCE(!shmem->pages) ||
557 	    shmem->madv < 0) {
558 		ret = VM_FAULT_SIGBUS;
559 	} else {
560 		page = shmem->pages[page_offset];
561 
562 		ret = vmf_insert_pfn(vma, vmf->address, page_to_pfn(page));
563 	}
564 
565 	mutex_unlock(&shmem->pages_lock);
566 
567 	return ret;
568 }
569 
570 static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
571 {
572 	struct drm_gem_object *obj = vma->vm_private_data;
573 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
574 	int ret;
575 
576 	WARN_ON(shmem->base.import_attach);
577 
578 	ret = drm_gem_shmem_get_pages(shmem);
579 	WARN_ON_ONCE(ret != 0);
580 
581 	drm_gem_vm_open(vma);
582 }
583 
584 static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
585 {
586 	struct drm_gem_object *obj = vma->vm_private_data;
587 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
588 
589 	drm_gem_shmem_put_pages(shmem);
590 	drm_gem_vm_close(vma);
591 }
592 
593 const struct vm_operations_struct drm_gem_shmem_vm_ops = {
594 	.fault = drm_gem_shmem_fault,
595 	.open = drm_gem_shmem_vm_open,
596 	.close = drm_gem_shmem_vm_close,
597 };
598 EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
599 
600 /**
601  * drm_gem_shmem_mmap - Memory-map a shmem GEM object
602  * @shmem: shmem GEM object
603  * @vma: VMA for the area to be mapped
604  *
605  * This function implements an augmented version of the GEM DRM file mmap
606  * operation for shmem objects.
607  *
608  * Returns:
609  * 0 on success or a negative error code on failure.
610  */
611 int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma)
612 {
613 	struct drm_gem_object *obj = &shmem->base;
614 	int ret;
615 
616 	if (obj->import_attach) {
617 		/* Drop the reference drm_gem_mmap_obj() acquired.*/
618 		drm_gem_object_put(obj);
619 		vma->vm_private_data = NULL;
620 
621 		return dma_buf_mmap(obj->dma_buf, vma, 0);
622 	}
623 
624 	ret = drm_gem_shmem_get_pages(shmem);
625 	if (ret) {
626 		drm_gem_vm_close(vma);
627 		return ret;
628 	}
629 
630 	vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
631 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
632 	if (shmem->map_wc)
633 		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
634 
635 	return 0;
636 }
637 EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
638 
639 /**
640  * drm_gem_shmem_print_info() - Print &drm_gem_shmem_object info for debugfs
641  * @shmem: shmem GEM object
642  * @p: DRM printer
643  * @indent: Tab indentation level
644  */
645 void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
646 			      struct drm_printer *p, unsigned int indent)
647 {
648 	drm_printf_indent(p, indent, "pages_use_count=%u\n", shmem->pages_use_count);
649 	drm_printf_indent(p, indent, "vmap_use_count=%u\n", shmem->vmap_use_count);
650 	drm_printf_indent(p, indent, "vaddr=%p\n", shmem->vaddr);
651 }
652 EXPORT_SYMBOL(drm_gem_shmem_print_info);
653 
654 /**
655  * drm_gem_shmem_get_sg_table - Provide a scatter/gather table of pinned
656  *                              pages for a shmem GEM object
657  * @shmem: shmem GEM object
658  *
659  * This function exports a scatter/gather table suitable for PRIME usage by
660  * calling the standard DMA mapping API.
661  *
662  * Drivers who need to acquire an scatter/gather table for objects need to call
663  * drm_gem_shmem_get_pages_sgt() instead.
664  *
665  * Returns:
666  * A pointer to the scatter/gather table of pinned pages or NULL on failure.
667  */
668 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
669 {
670 	struct drm_gem_object *obj = &shmem->base;
671 
672 	WARN_ON(shmem->base.import_attach);
673 
674 	return drm_prime_pages_to_sg(obj->dev, shmem->pages, obj->size >> PAGE_SHIFT);
675 }
676 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
677 
678 /**
679  * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
680  *				 scatter/gather table for a shmem GEM object.
681  * @shmem: shmem GEM object
682  *
683  * This function returns a scatter/gather table suitable for driver usage. If
684  * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg
685  * table created.
686  *
687  * This is the main function for drivers to get at backing storage, and it hides
688  * and difference between dma-buf imported and natively allocated objects.
689  * drm_gem_shmem_get_sg_table() should not be directly called by drivers.
690  *
691  * Returns:
692  * A pointer to the scatter/gather table of pinned pages or errno on failure.
693  */
694 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)
695 {
696 	struct drm_gem_object *obj = &shmem->base;
697 	int ret;
698 	struct sg_table *sgt;
699 
700 	if (shmem->sgt)
701 		return shmem->sgt;
702 
703 	WARN_ON(obj->import_attach);
704 
705 	ret = drm_gem_shmem_get_pages(shmem);
706 	if (ret)
707 		return ERR_PTR(ret);
708 
709 	sgt = drm_gem_shmem_get_sg_table(shmem);
710 	if (IS_ERR(sgt)) {
711 		ret = PTR_ERR(sgt);
712 		goto err_put_pages;
713 	}
714 	/* Map the pages for use by the h/w. */
715 	ret = dma_map_sgtable(obj->dev->dev, sgt, DMA_BIDIRECTIONAL, 0);
716 	if (ret)
717 		goto err_free_sgt;
718 
719 	shmem->sgt = sgt;
720 
721 	return sgt;
722 
723 err_free_sgt:
724 	sg_free_table(sgt);
725 	kfree(sgt);
726 err_put_pages:
727 	drm_gem_shmem_put_pages(shmem);
728 	return ERR_PTR(ret);
729 }
730 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);
731 
732 /**
733  * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from
734  *                 another driver's scatter/gather table of pinned pages
735  * @dev: Device to import into
736  * @attach: DMA-BUF attachment
737  * @sgt: Scatter/gather table of pinned pages
738  *
739  * This function imports a scatter/gather table exported via DMA-BUF by
740  * another driver. Drivers that use the shmem helpers should set this as their
741  * &drm_driver.gem_prime_import_sg_table callback.
742  *
743  * Returns:
744  * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
745  * error code on failure.
746  */
747 struct drm_gem_object *
748 drm_gem_shmem_prime_import_sg_table(struct drm_device *dev,
749 				    struct dma_buf_attachment *attach,
750 				    struct sg_table *sgt)
751 {
752 	size_t size = PAGE_ALIGN(attach->dmabuf->size);
753 	struct drm_gem_shmem_object *shmem;
754 
755 	shmem = __drm_gem_shmem_create(dev, size, true);
756 	if (IS_ERR(shmem))
757 		return ERR_CAST(shmem);
758 
759 	shmem->sgt = sgt;
760 
761 	DRM_DEBUG_PRIME("size = %zu\n", size);
762 
763 	return &shmem->base;
764 }
765 EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table);
766 
767 MODULE_DESCRIPTION("DRM SHMEM memory-management helpers");
768 MODULE_IMPORT_NS(DMA_BUF);
769 MODULE_LICENSE("GPL v2");
770