1 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
2 /**************************************************************************
3  *
4  * Copyright (c) 2009-2013 VMware, Inc., Palo Alto, CA., USA
5  * All Rights Reserved.
6  *
7  * Permission is hereby granted, free of charge, to any person obtaining a
8  * copy of this software and associated documentation files (the
9  * "Software"), to deal in the Software without restriction, including
10  * without limitation the rights to use, copy, modify, merge, publish,
11  * distribute, sub license, and/or sell copies of the Software, and to
12  * permit persons to whom the Software is furnished to do so, subject to
13  * the following conditions:
14  *
15  * The above copyright notice and this permission notice (including the
16  * next paragraph) shall be included in all copies or substantial portions
17  * of the Software.
18  *
19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
22  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
23  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
24  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
25  * USE OR OTHER DEALINGS IN THE SOFTWARE.
26  *
27  **************************************************************************/
28 /*
29  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
30  *
31  * While no substantial code is shared, the prime code is inspired by
32  * drm_prime.c, with
33  * Authors:
34  *      Dave Airlie <airlied@redhat.com>
35  *      Rob Clark <rob.clark@linaro.org>
36  */
37 /** @file ttm_ref_object.c
38  *
39  * Base- and reference object implementation for the various
40  * ttm objects. Implements reference counting, minimal security checks
41  * and release on file close.
42  */
43 
44 
45 /**
46  * struct ttm_object_file
47  *
48  * @tdev: Pointer to the ttm_object_device.
49  *
50  * @lock: Lock that protects the ref_list list and the
51  * ref_hash hash tables.
52  *
53  * @ref_list: List of ttm_ref_objects to be destroyed at
54  * file release.
55  *
56  * @ref_hash: Hash tables of ref objects, one per ttm_ref_type,
57  * for fast lookup of ref objects given a base object.
58  */
59 
60 #define pr_fmt(fmt) "[TTM] " fmt
61 
62 #include <drm/ttm/ttm_module.h>
63 #include <linux/list.h>
64 #include <linux/spinlock.h>
65 #include <linux/slab.h>
66 #include <linux/atomic.h>
67 #include "ttm_object.h"
68 
69 struct ttm_object_file {
70 	struct ttm_object_device *tdev;
71 	spinlock_t lock;
72 	struct list_head ref_list;
73 	struct drm_open_hash ref_hash[TTM_REF_NUM];
74 	struct kref refcount;
75 };
76 
77 /**
78  * struct ttm_object_device
79  *
80  * @object_lock: lock that protects the object_hash hash table.
81  *
82  * @object_hash: hash table for fast lookup of object global names.
83  *
84  * @object_count: Per device object count.
85  *
86  * This is the per-device data structure needed for ttm object management.
87  */
88 
89 struct ttm_object_device {
90 	spinlock_t object_lock;
91 	struct drm_open_hash object_hash;
92 	atomic_t object_count;
93 	struct ttm_mem_global *mem_glob;
94 	struct dma_buf_ops ops;
95 	void (*dmabuf_release)(struct dma_buf *dma_buf);
96 	size_t dma_buf_size;
97 	struct idr idr;
98 };
99 
100 /**
101  * struct ttm_ref_object
102  *
103  * @hash: Hash entry for the per-file object reference hash.
104  *
105  * @head: List entry for the per-file list of ref-objects.
106  *
107  * @kref: Ref count.
108  *
109  * @obj: Base object this ref object is referencing.
110  *
111  * @ref_type: Type of ref object.
112  *
113  * This is similar to an idr object, but it also has a hash table entry
114  * that allows lookup with a pointer to the referenced object as a key. In
115  * that way, one can easily detect whether a base object is referenced by
116  * a particular ttm_object_file. It also carries a ref count to avoid creating
117  * multiple ref objects if a ttm_object_file references the same base
118  * object more than once.
119  */
120 
121 struct ttm_ref_object {
122 	struct rcu_head rcu_head;
123 	struct drm_hash_item hash;
124 	struct list_head head;
125 	struct kref kref;
126 	enum ttm_ref_type ref_type;
127 	struct ttm_base_object *obj;
128 	struct ttm_object_file *tfile;
129 };
130 
131 static void ttm_prime_dmabuf_release(struct dma_buf *dma_buf);
132 
133 static inline struct ttm_object_file *
134 ttm_object_file_ref(struct ttm_object_file *tfile)
135 {
136 	kref_get(&tfile->refcount);
137 	return tfile;
138 }
139 
140 static void ttm_object_file_destroy(struct kref *kref)
141 {
142 	struct ttm_object_file *tfile =
143 		container_of(kref, struct ttm_object_file, refcount);
144 
145 	kfree(tfile);
146 }
147 
148 
149 static inline void ttm_object_file_unref(struct ttm_object_file **p_tfile)
150 {
151 	struct ttm_object_file *tfile = *p_tfile;
152 
153 	*p_tfile = NULL;
154 	kref_put(&tfile->refcount, ttm_object_file_destroy);
155 }
156 
157 
158 int ttm_base_object_init(struct ttm_object_file *tfile,
159 			 struct ttm_base_object *base,
160 			 bool shareable,
161 			 enum ttm_object_type object_type,
162 			 void (*refcount_release) (struct ttm_base_object **),
163 			 void (*ref_obj_release) (struct ttm_base_object *,
164 						  enum ttm_ref_type ref_type))
165 {
166 	struct ttm_object_device *tdev = tfile->tdev;
167 	int ret;
168 
169 	base->shareable = shareable;
170 	base->tfile = ttm_object_file_ref(tfile);
171 	base->refcount_release = refcount_release;
172 	base->ref_obj_release = ref_obj_release;
173 	base->object_type = object_type;
174 	kref_init(&base->refcount);
175 	idr_preload(GFP_KERNEL);
176 	spin_lock(&tdev->object_lock);
177 	ret = idr_alloc(&tdev->idr, base, 1, 0, GFP_NOWAIT);
178 	spin_unlock(&tdev->object_lock);
179 	idr_preload_end();
180 	if (ret < 0)
181 		return ret;
182 
183 	base->handle = ret;
184 	ret = ttm_ref_object_add(tfile, base, TTM_REF_USAGE, NULL, false);
185 	if (unlikely(ret != 0))
186 		goto out_err1;
187 
188 	ttm_base_object_unref(&base);
189 
190 	return 0;
191 out_err1:
192 	spin_lock(&tdev->object_lock);
193 	idr_remove(&tdev->idr, base->handle);
194 	spin_unlock(&tdev->object_lock);
195 	return ret;
196 }
197 
198 static void ttm_release_base(struct kref *kref)
199 {
200 	struct ttm_base_object *base =
201 	    container_of(kref, struct ttm_base_object, refcount);
202 	struct ttm_object_device *tdev = base->tfile->tdev;
203 
204 	spin_lock(&tdev->object_lock);
205 	idr_remove(&tdev->idr, base->handle);
206 	spin_unlock(&tdev->object_lock);
207 
208 	/*
209 	 * Note: We don't use synchronize_rcu() here because it's far
210 	 * too slow. It's up to the user to free the object using
211 	 * call_rcu() or ttm_base_object_kfree().
212 	 */
213 
214 	ttm_object_file_unref(&base->tfile);
215 	if (base->refcount_release)
216 		base->refcount_release(&base);
217 }
218 
219 void ttm_base_object_unref(struct ttm_base_object **p_base)
220 {
221 	struct ttm_base_object *base = *p_base;
222 
223 	*p_base = NULL;
224 
225 	kref_put(&base->refcount, ttm_release_base);
226 }
227 
228 /**
229  * ttm_base_object_noref_lookup - look up a base object without reference
230  * @tfile: The struct ttm_object_file the object is registered with.
231  * @key: The object handle.
232  *
233  * This function looks up a ttm base object and returns a pointer to it
234  * without refcounting the pointer. The returned pointer is only valid
235  * until ttm_base_object_noref_release() is called, and the object
236  * pointed to by the returned pointer may be doomed. Any persistent usage
237  * of the object requires a refcount to be taken using kref_get_unless_zero().
238  * Iff this function returns successfully it needs to be paired with
239  * ttm_base_object_noref_release() and no sleeping- or scheduling functions
240  * may be called inbetween these function callse.
241  *
242  * Return: A pointer to the object if successful or NULL otherwise.
243  */
244 struct ttm_base_object *
245 ttm_base_object_noref_lookup(struct ttm_object_file *tfile, uint32_t key)
246 {
247 	struct drm_hash_item *hash;
248 	struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
249 	int ret;
250 
251 	rcu_read_lock();
252 	ret = drm_ht_find_item_rcu(ht, key, &hash);
253 	if (ret) {
254 		rcu_read_unlock();
255 		return NULL;
256 	}
257 
258 	__release(RCU);
259 	return drm_hash_entry(hash, struct ttm_ref_object, hash)->obj;
260 }
261 EXPORT_SYMBOL(ttm_base_object_noref_lookup);
262 
263 struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile,
264 					       uint32_t key)
265 {
266 	struct ttm_base_object *base = NULL;
267 	struct drm_hash_item *hash;
268 	struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
269 	int ret;
270 
271 	rcu_read_lock();
272 	ret = drm_ht_find_item_rcu(ht, key, &hash);
273 
274 	if (likely(ret == 0)) {
275 		base = drm_hash_entry(hash, struct ttm_ref_object, hash)->obj;
276 		if (!kref_get_unless_zero(&base->refcount))
277 			base = NULL;
278 	}
279 	rcu_read_unlock();
280 
281 	return base;
282 }
283 
284 struct ttm_base_object *
285 ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint32_t key)
286 {
287 	struct ttm_base_object *base;
288 
289 	rcu_read_lock();
290 	base = idr_find(&tdev->idr, key);
291 
292 	if (base && !kref_get_unless_zero(&base->refcount))
293 		base = NULL;
294 	rcu_read_unlock();
295 
296 	return base;
297 }
298 
299 /**
300  * ttm_ref_object_exists - Check whether a caller has a valid ref object
301  * (has opened) a base object.
302  *
303  * @tfile: Pointer to a struct ttm_object_file identifying the caller.
304  * @base: Pointer to a struct base object.
305  *
306  * Checks wether the caller identified by @tfile has put a valid USAGE
307  * reference object on the base object identified by @base.
308  */
309 bool ttm_ref_object_exists(struct ttm_object_file *tfile,
310 			   struct ttm_base_object *base)
311 {
312 	struct drm_open_hash *ht = &tfile->ref_hash[TTM_REF_USAGE];
313 	struct drm_hash_item *hash;
314 	struct ttm_ref_object *ref;
315 
316 	rcu_read_lock();
317 	if (unlikely(drm_ht_find_item_rcu(ht, base->handle, &hash) != 0))
318 		goto out_false;
319 
320 	/*
321 	 * Verify that the ref object is really pointing to our base object.
322 	 * Our base object could actually be dead, and the ref object pointing
323 	 * to another base object with the same handle.
324 	 */
325 	ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
326 	if (unlikely(base != ref->obj))
327 		goto out_false;
328 
329 	/*
330 	 * Verify that the ref->obj pointer was actually valid!
331 	 */
332 	rmb();
333 	if (unlikely(kref_read(&ref->kref) == 0))
334 		goto out_false;
335 
336 	rcu_read_unlock();
337 	return true;
338 
339  out_false:
340 	rcu_read_unlock();
341 	return false;
342 }
343 
344 int ttm_ref_object_add(struct ttm_object_file *tfile,
345 		       struct ttm_base_object *base,
346 		       enum ttm_ref_type ref_type, bool *existed,
347 		       bool require_existed)
348 {
349 	struct drm_open_hash *ht = &tfile->ref_hash[ref_type];
350 	struct ttm_ref_object *ref;
351 	struct drm_hash_item *hash;
352 	struct ttm_mem_global *mem_glob = tfile->tdev->mem_glob;
353 	struct ttm_operation_ctx ctx = {
354 		.interruptible = false,
355 		.no_wait_gpu = false
356 	};
357 	int ret = -EINVAL;
358 
359 	if (base->tfile != tfile && !base->shareable)
360 		return -EPERM;
361 
362 	if (existed != NULL)
363 		*existed = true;
364 
365 	while (ret == -EINVAL) {
366 		rcu_read_lock();
367 		ret = drm_ht_find_item_rcu(ht, base->handle, &hash);
368 
369 		if (ret == 0) {
370 			ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
371 			if (kref_get_unless_zero(&ref->kref)) {
372 				rcu_read_unlock();
373 				break;
374 			}
375 		}
376 
377 		rcu_read_unlock();
378 		if (require_existed)
379 			return -EPERM;
380 
381 		ret = ttm_mem_global_alloc(mem_glob, sizeof(*ref),
382 					   &ctx);
383 		if (unlikely(ret != 0))
384 			return ret;
385 		ref = kmalloc(sizeof(*ref), GFP_KERNEL);
386 		if (unlikely(ref == NULL)) {
387 			ttm_mem_global_free(mem_glob, sizeof(*ref));
388 			return -ENOMEM;
389 		}
390 
391 		ref->hash.key = base->handle;
392 		ref->obj = base;
393 		ref->tfile = tfile;
394 		ref->ref_type = ref_type;
395 		kref_init(&ref->kref);
396 
397 		spin_lock(&tfile->lock);
398 		ret = drm_ht_insert_item_rcu(ht, &ref->hash);
399 
400 		if (likely(ret == 0)) {
401 			list_add_tail(&ref->head, &tfile->ref_list);
402 			kref_get(&base->refcount);
403 			spin_unlock(&tfile->lock);
404 			if (existed != NULL)
405 				*existed = false;
406 			break;
407 		}
408 
409 		spin_unlock(&tfile->lock);
410 		BUG_ON(ret != -EINVAL);
411 
412 		ttm_mem_global_free(mem_glob, sizeof(*ref));
413 		kfree(ref);
414 	}
415 
416 	return ret;
417 }
418 
419 static void __releases(tfile->lock) __acquires(tfile->lock)
420 ttm_ref_object_release(struct kref *kref)
421 {
422 	struct ttm_ref_object *ref =
423 	    container_of(kref, struct ttm_ref_object, kref);
424 	struct ttm_base_object *base = ref->obj;
425 	struct ttm_object_file *tfile = ref->tfile;
426 	struct drm_open_hash *ht;
427 	struct ttm_mem_global *mem_glob = tfile->tdev->mem_glob;
428 
429 	ht = &tfile->ref_hash[ref->ref_type];
430 	(void)drm_ht_remove_item_rcu(ht, &ref->hash);
431 	list_del(&ref->head);
432 	spin_unlock(&tfile->lock);
433 
434 	if (ref->ref_type != TTM_REF_USAGE && base->ref_obj_release)
435 		base->ref_obj_release(base, ref->ref_type);
436 
437 	ttm_base_object_unref(&ref->obj);
438 	ttm_mem_global_free(mem_glob, sizeof(*ref));
439 	kfree_rcu(ref, rcu_head);
440 	spin_lock(&tfile->lock);
441 }
442 
443 int ttm_ref_object_base_unref(struct ttm_object_file *tfile,
444 			      unsigned long key, enum ttm_ref_type ref_type)
445 {
446 	struct drm_open_hash *ht = &tfile->ref_hash[ref_type];
447 	struct ttm_ref_object *ref;
448 	struct drm_hash_item *hash;
449 	int ret;
450 
451 	spin_lock(&tfile->lock);
452 	ret = drm_ht_find_item(ht, key, &hash);
453 	if (unlikely(ret != 0)) {
454 		spin_unlock(&tfile->lock);
455 		return -EINVAL;
456 	}
457 	ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
458 	kref_put(&ref->kref, ttm_ref_object_release);
459 	spin_unlock(&tfile->lock);
460 	return 0;
461 }
462 
463 void ttm_object_file_release(struct ttm_object_file **p_tfile)
464 {
465 	struct ttm_ref_object *ref;
466 	struct list_head *list;
467 	unsigned int i;
468 	struct ttm_object_file *tfile = *p_tfile;
469 
470 	*p_tfile = NULL;
471 	spin_lock(&tfile->lock);
472 
473 	/*
474 	 * Since we release the lock within the loop, we have to
475 	 * restart it from the beginning each time.
476 	 */
477 
478 	while (!list_empty(&tfile->ref_list)) {
479 		list = tfile->ref_list.next;
480 		ref = list_entry(list, struct ttm_ref_object, head);
481 		ttm_ref_object_release(&ref->kref);
482 	}
483 
484 	spin_unlock(&tfile->lock);
485 	for (i = 0; i < TTM_REF_NUM; ++i)
486 		drm_ht_remove(&tfile->ref_hash[i]);
487 
488 	ttm_object_file_unref(&tfile);
489 }
490 
491 struct ttm_object_file *ttm_object_file_init(struct ttm_object_device *tdev,
492 					     unsigned int hash_order)
493 {
494 	struct ttm_object_file *tfile = kmalloc(sizeof(*tfile), GFP_KERNEL);
495 	unsigned int i;
496 	unsigned int j = 0;
497 	int ret;
498 
499 	if (unlikely(tfile == NULL))
500 		return NULL;
501 
502 	spin_lock_init(&tfile->lock);
503 	tfile->tdev = tdev;
504 	kref_init(&tfile->refcount);
505 	INIT_LIST_HEAD(&tfile->ref_list);
506 
507 	for (i = 0; i < TTM_REF_NUM; ++i) {
508 		ret = drm_ht_create(&tfile->ref_hash[i], hash_order);
509 		if (ret) {
510 			j = i;
511 			goto out_err;
512 		}
513 	}
514 
515 	return tfile;
516 out_err:
517 	for (i = 0; i < j; ++i)
518 		drm_ht_remove(&tfile->ref_hash[i]);
519 
520 	kfree(tfile);
521 
522 	return NULL;
523 }
524 
525 struct ttm_object_device *
526 ttm_object_device_init(struct ttm_mem_global *mem_glob,
527 		       unsigned int hash_order,
528 		       const struct dma_buf_ops *ops)
529 {
530 	struct ttm_object_device *tdev = kmalloc(sizeof(*tdev), GFP_KERNEL);
531 	int ret;
532 
533 	if (unlikely(tdev == NULL))
534 		return NULL;
535 
536 	tdev->mem_glob = mem_glob;
537 	spin_lock_init(&tdev->object_lock);
538 	atomic_set(&tdev->object_count, 0);
539 	ret = drm_ht_create(&tdev->object_hash, hash_order);
540 	if (ret != 0)
541 		goto out_no_object_hash;
542 
543 	idr_init(&tdev->idr);
544 	tdev->ops = *ops;
545 	tdev->dmabuf_release = tdev->ops.release;
546 	tdev->ops.release = ttm_prime_dmabuf_release;
547 	tdev->dma_buf_size = ttm_round_pot(sizeof(struct dma_buf)) +
548 		ttm_round_pot(sizeof(struct file));
549 	return tdev;
550 
551 out_no_object_hash:
552 	kfree(tdev);
553 	return NULL;
554 }
555 
556 void ttm_object_device_release(struct ttm_object_device **p_tdev)
557 {
558 	struct ttm_object_device *tdev = *p_tdev;
559 
560 	*p_tdev = NULL;
561 
562 	WARN_ON_ONCE(!idr_is_empty(&tdev->idr));
563 	idr_destroy(&tdev->idr);
564 	drm_ht_remove(&tdev->object_hash);
565 
566 	kfree(tdev);
567 }
568 
569 /**
570  * get_dma_buf_unless_doomed - get a dma_buf reference if possible.
571  *
572  * @dma_buf: Non-refcounted pointer to a struct dma-buf.
573  *
574  * Obtain a file reference from a lookup structure that doesn't refcount
575  * the file, but synchronizes with its release method to make sure it has
576  * not been freed yet. See for example kref_get_unless_zero documentation.
577  * Returns true if refcounting succeeds, false otherwise.
578  *
579  * Nobody really wants this as a public API yet, so let it mature here
580  * for some time...
581  */
582 static bool __must_check get_dma_buf_unless_doomed(struct dma_buf *dmabuf)
583 {
584 	return atomic_long_inc_not_zero(&dmabuf->file->f_count) != 0L;
585 }
586 
587 /**
588  * ttm_prime_refcount_release - refcount release method for a prime object.
589  *
590  * @p_base: Pointer to ttm_base_object pointer.
591  *
592  * This is a wrapper that calls the refcount_release founction of the
593  * underlying object. At the same time it cleans up the prime object.
594  * This function is called when all references to the base object we
595  * derive from are gone.
596  */
597 static void ttm_prime_refcount_release(struct ttm_base_object **p_base)
598 {
599 	struct ttm_base_object *base = *p_base;
600 	struct ttm_prime_object *prime;
601 
602 	*p_base = NULL;
603 	prime = container_of(base, struct ttm_prime_object, base);
604 	BUG_ON(prime->dma_buf != NULL);
605 	mutex_destroy(&prime->mutex);
606 	if (prime->refcount_release)
607 		prime->refcount_release(&base);
608 }
609 
610 /**
611  * ttm_prime_dmabuf_release - Release method for the dma-bufs we export
612  *
613  * @dma_buf:
614  *
615  * This function first calls the dma_buf release method the driver
616  * provides. Then it cleans up our dma_buf pointer used for lookup,
617  * and finally releases the reference the dma_buf has on our base
618  * object.
619  */
620 static void ttm_prime_dmabuf_release(struct dma_buf *dma_buf)
621 {
622 	struct ttm_prime_object *prime =
623 		(struct ttm_prime_object *) dma_buf->priv;
624 	struct ttm_base_object *base = &prime->base;
625 	struct ttm_object_device *tdev = base->tfile->tdev;
626 
627 	if (tdev->dmabuf_release)
628 		tdev->dmabuf_release(dma_buf);
629 	mutex_lock(&prime->mutex);
630 	if (prime->dma_buf == dma_buf)
631 		prime->dma_buf = NULL;
632 	mutex_unlock(&prime->mutex);
633 	ttm_mem_global_free(tdev->mem_glob, tdev->dma_buf_size);
634 	ttm_base_object_unref(&base);
635 }
636 
637 /**
638  * ttm_prime_fd_to_handle - Get a base object handle from a prime fd
639  *
640  * @tfile: A struct ttm_object_file identifying the caller.
641  * @fd: The prime / dmabuf fd.
642  * @handle: The returned handle.
643  *
644  * This function returns a handle to an object that previously exported
645  * a dma-buf. Note that we don't handle imports yet, because we simply
646  * have no consumers of that implementation.
647  */
648 int ttm_prime_fd_to_handle(struct ttm_object_file *tfile,
649 			   int fd, u32 *handle)
650 {
651 	struct ttm_object_device *tdev = tfile->tdev;
652 	struct dma_buf *dma_buf;
653 	struct ttm_prime_object *prime;
654 	struct ttm_base_object *base;
655 	int ret;
656 
657 	dma_buf = dma_buf_get(fd);
658 	if (IS_ERR(dma_buf))
659 		return PTR_ERR(dma_buf);
660 
661 	if (dma_buf->ops != &tdev->ops)
662 		return -ENOSYS;
663 
664 	prime = (struct ttm_prime_object *) dma_buf->priv;
665 	base = &prime->base;
666 	*handle = base->handle;
667 	ret = ttm_ref_object_add(tfile, base, TTM_REF_USAGE, NULL, false);
668 
669 	dma_buf_put(dma_buf);
670 
671 	return ret;
672 }
673 
674 /**
675  * ttm_prime_handle_to_fd - Return a dma_buf fd from a ttm prime object
676  *
677  * @tfile: Struct ttm_object_file identifying the caller.
678  * @handle: Handle to the object we're exporting from.
679  * @flags: flags for dma-buf creation. We just pass them on.
680  * @prime_fd: The returned file descriptor.
681  *
682  */
683 int ttm_prime_handle_to_fd(struct ttm_object_file *tfile,
684 			   uint32_t handle, uint32_t flags,
685 			   int *prime_fd)
686 {
687 	struct ttm_object_device *tdev = tfile->tdev;
688 	struct ttm_base_object *base;
689 	struct dma_buf *dma_buf;
690 	struct ttm_prime_object *prime;
691 	int ret;
692 
693 	base = ttm_base_object_lookup(tfile, handle);
694 	if (unlikely(base == NULL ||
695 		     base->object_type != ttm_prime_type)) {
696 		ret = -ENOENT;
697 		goto out_unref;
698 	}
699 
700 	prime = container_of(base, struct ttm_prime_object, base);
701 	if (unlikely(!base->shareable)) {
702 		ret = -EPERM;
703 		goto out_unref;
704 	}
705 
706 	ret = mutex_lock_interruptible(&prime->mutex);
707 	if (unlikely(ret != 0)) {
708 		ret = -ERESTARTSYS;
709 		goto out_unref;
710 	}
711 
712 	dma_buf = prime->dma_buf;
713 	if (!dma_buf || !get_dma_buf_unless_doomed(dma_buf)) {
714 		DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
715 		struct ttm_operation_ctx ctx = {
716 			.interruptible = true,
717 			.no_wait_gpu = false
718 		};
719 		exp_info.ops = &tdev->ops;
720 		exp_info.size = prime->size;
721 		exp_info.flags = flags;
722 		exp_info.priv = prime;
723 
724 		/*
725 		 * Need to create a new dma_buf, with memory accounting.
726 		 */
727 		ret = ttm_mem_global_alloc(tdev->mem_glob, tdev->dma_buf_size,
728 					   &ctx);
729 		if (unlikely(ret != 0)) {
730 			mutex_unlock(&prime->mutex);
731 			goto out_unref;
732 		}
733 
734 		dma_buf = dma_buf_export(&exp_info);
735 		if (IS_ERR(dma_buf)) {
736 			ret = PTR_ERR(dma_buf);
737 			ttm_mem_global_free(tdev->mem_glob,
738 					    tdev->dma_buf_size);
739 			mutex_unlock(&prime->mutex);
740 			goto out_unref;
741 		}
742 
743 		/*
744 		 * dma_buf has taken the base object reference
745 		 */
746 		base = NULL;
747 		prime->dma_buf = dma_buf;
748 	}
749 	mutex_unlock(&prime->mutex);
750 
751 	ret = dma_buf_fd(dma_buf, flags);
752 	if (ret >= 0) {
753 		*prime_fd = ret;
754 		ret = 0;
755 	} else
756 		dma_buf_put(dma_buf);
757 
758 out_unref:
759 	if (base)
760 		ttm_base_object_unref(&base);
761 	return ret;
762 }
763 
764 /**
765  * ttm_prime_object_init - Initialize a ttm_prime_object
766  *
767  * @tfile: struct ttm_object_file identifying the caller
768  * @size: The size of the dma_bufs we export.
769  * @prime: The object to be initialized.
770  * @shareable: See ttm_base_object_init
771  * @type: See ttm_base_object_init
772  * @refcount_release: See ttm_base_object_init
773  * @ref_obj_release: See ttm_base_object_init
774  *
775  * Initializes an object which is compatible with the drm_prime model
776  * for data sharing between processes and devices.
777  */
778 int ttm_prime_object_init(struct ttm_object_file *tfile, size_t size,
779 			  struct ttm_prime_object *prime, bool shareable,
780 			  enum ttm_object_type type,
781 			  void (*refcount_release) (struct ttm_base_object **),
782 			  void (*ref_obj_release) (struct ttm_base_object *,
783 						   enum ttm_ref_type ref_type))
784 {
785 	mutex_init(&prime->mutex);
786 	prime->size = PAGE_ALIGN(size);
787 	prime->real_type = type;
788 	prime->dma_buf = NULL;
789 	prime->refcount_release = refcount_release;
790 	return ttm_base_object_init(tfile, &prime->base, shareable,
791 				    ttm_prime_type,
792 				    ttm_prime_refcount_release,
793 				    ref_obj_release);
794 }
795