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1/*
2 * System Trace Module (STM) infrastructure
3 * Copyright (c) 2014, Intel Corporation.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 *
14 * STM class implements generic infrastructure for System Trace Module devices
15 * as defined in MIPI STPv2 specification.
16 */
17
18#include <linux/uaccess.h>
19#include <linux/kernel.h>
20#include <linux/module.h>
21#include <linux/device.h>
22#include <linux/compat.h>
23#include <linux/kdev_t.h>
24#include <linux/srcu.h>
25#include <linux/slab.h>
26#include <linux/stm.h>
27#include <linux/fs.h>
28#include <linux/mm.h>
29#include "stm.h"
30
31#include <uapi/linux/stm.h>
32
33static unsigned int stm_core_up;
34
35/*
36 * The SRCU here makes sure that STM device doesn't disappear from under a
37 * stm_source_write() caller, which may want to have as little overhead as
38 * possible.
39 */
40static struct srcu_struct stm_source_srcu;
41
42static ssize_t masters_show(struct device *dev,
43 struct device_attribute *attr,
44 char *buf)
45{
46 struct stm_device *stm = to_stm_device(dev);
47 int ret;
48
49 ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);
50
51 return ret;
52}
53
54static DEVICE_ATTR_RO(masters);
55
56static ssize_t channels_show(struct device *dev,
57 struct device_attribute *attr,
58 char *buf)
59{
60 struct stm_device *stm = to_stm_device(dev);
61 int ret;
62
63 ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);
64
65 return ret;
66}
67
68static DEVICE_ATTR_RO(channels);
69
70static struct attribute *stm_attrs[] = {
71 &dev_attr_masters.attr,
72 &dev_attr_channels.attr,
73 NULL,
74};
75
76ATTRIBUTE_GROUPS(stm);
77
78static struct class stm_class = {
79 .name = "stm",
80 .dev_groups = stm_groups,
81};
82
83static int stm_dev_match(struct device *dev, const void *data)
84{
85 const char *name = data;
86
87 return sysfs_streq(name, dev_name(dev));
88}
89
90/**
91 * stm_find_device() - find stm device by name
92 * @buf: character buffer containing the name
93 *
94 * This is called when either policy gets assigned to an stm device or an
95 * stm_source device gets linked to an stm device.
96 *
97 * This grabs device's reference (get_device()) and module reference, both
98 * of which the calling path needs to make sure to drop with stm_put_device().
99 *
100 * Return: stm device pointer or null if lookup failed.
101 */
102struct stm_device *stm_find_device(const char *buf)
103{
104 struct stm_device *stm;
105 struct device *dev;
106
107 if (!stm_core_up)
108 return NULL;
109
110 dev = class_find_device(&stm_class, NULL, buf, stm_dev_match);
111 if (!dev)
112 return NULL;
113
114 stm = to_stm_device(dev);
115 if (!try_module_get(stm->owner)) {
116 /* matches class_find_device() above */
117 put_device(dev);
118 return NULL;
119 }
120
121 return stm;
122}
123
124/**
125 * stm_put_device() - drop references on the stm device
126 * @stm: stm device, previously acquired by stm_find_device()
127 *
128 * This drops the module reference and device reference taken by
129 * stm_find_device() or stm_char_open().
130 */
131void stm_put_device(struct stm_device *stm)
132{
133 module_put(stm->owner);
134 put_device(&stm->dev);
135}
136
137/*
138 * Internally we only care about software-writable masters here, that is the
139 * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
140 * original master numbers to be visible externally, since they are the ones
141 * that will appear in the STP stream. Thus, the internal bookkeeping uses
142 * $master - stm_data->sw_start to reference master descriptors and such.
143 */
144
145#define __stm_master(_s, _m) \
146 ((_s)->masters[(_m) - (_s)->data->sw_start])
147
148static inline struct stp_master *
149stm_master(struct stm_device *stm, unsigned int idx)
150{
151 if (idx < stm->data->sw_start || idx > stm->data->sw_end)
152 return NULL;
153
154 return __stm_master(stm, idx);
155}
156
157static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
158{
159 struct stp_master *master;
160 size_t size;
161
162 size = ALIGN(stm->data->sw_nchannels, 8) / 8;
163 size += sizeof(struct stp_master);
164 master = kzalloc(size, GFP_ATOMIC);
165 if (!master)
166 return -ENOMEM;
167
168 master->nr_free = stm->data->sw_nchannels;
169 __stm_master(stm, idx) = master;
170
171 return 0;
172}
173
174static void stp_master_free(struct stm_device *stm, unsigned int idx)
175{
176 struct stp_master *master = stm_master(stm, idx);
177
178 if (!master)
179 return;
180
181 __stm_master(stm, idx) = NULL;
182 kfree(master);
183}
184
185static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
186{
187 struct stp_master *master = stm_master(stm, output->master);
188
189 lockdep_assert_held(&stm->mc_lock);
190 lockdep_assert_held(&output->lock);
191
192 if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
193 return;
194
195 bitmap_allocate_region(&master->chan_map[0], output->channel,
196 ilog2(output->nr_chans));
197
198 master->nr_free -= output->nr_chans;
199}
200
201static void
202stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
203{
204 struct stp_master *master = stm_master(stm, output->master);
205
206 lockdep_assert_held(&stm->mc_lock);
207 lockdep_assert_held(&output->lock);
208
209 bitmap_release_region(&master->chan_map[0], output->channel,
210 ilog2(output->nr_chans));
211
212 output->nr_chans = 0;
213 master->nr_free += output->nr_chans;
214}
215
216/*
217 * This is like bitmap_find_free_region(), except it can ignore @start bits
218 * at the beginning.
219 */
220static int find_free_channels(unsigned long *bitmap, unsigned int start,
221 unsigned int end, unsigned int width)
222{
223 unsigned int pos;
224 int i;
225
226 for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
227 pos = find_next_zero_bit(bitmap, end + 1, pos);
228 if (pos + width > end + 1)
229 break;
230
231 if (pos & (width - 1))
232 continue;
233
234 for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
235 ;
236 if (i == width)
237 return pos;
238 }
239
240 return -1;
241}
242
243static int
244stm_find_master_chan(struct stm_device *stm, unsigned int width,
245 unsigned int *mstart, unsigned int mend,
246 unsigned int *cstart, unsigned int cend)
247{
248 struct stp_master *master;
249 unsigned int midx;
250 int pos, err;
251
252 for (midx = *mstart; midx <= mend; midx++) {
253 if (!stm_master(stm, midx)) {
254 err = stp_master_alloc(stm, midx);
255 if (err)
256 return err;
257 }
258
259 master = stm_master(stm, midx);
260
261 if (!master->nr_free)
262 continue;
263
264 pos = find_free_channels(master->chan_map, *cstart, cend,
265 width);
266 if (pos < 0)
267 continue;
268
269 *mstart = midx;
270 *cstart = pos;
271 return 0;
272 }
273
274 return -ENOSPC;
275}
276
277static int stm_output_assign(struct stm_device *stm, unsigned int width,
278 struct stp_policy_node *policy_node,
279 struct stm_output *output)
280{
281 unsigned int midx, cidx, mend, cend;
282 int ret = -EINVAL;
283
284 if (width > stm->data->sw_nchannels)
285 return -EINVAL;
286
287 if (policy_node) {
288 stp_policy_node_get_ranges(policy_node,
289 &midx, &mend, &cidx, &cend);
290 } else {
291 midx = stm->data->sw_start;
292 cidx = 0;
293 mend = stm->data->sw_end;
294 cend = stm->data->sw_nchannels - 1;
295 }
296
297 spin_lock(&stm->mc_lock);
298 spin_lock(&output->lock);
299 /* output is already assigned -- shouldn't happen */
300 if (WARN_ON_ONCE(output->nr_chans))
301 goto unlock;
302
303 ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
304 if (ret < 0)
305 goto unlock;
306
307 output->master = midx;
308 output->channel = cidx;
309 output->nr_chans = width;
310 stm_output_claim(stm, output);
311 dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
312
313 ret = 0;
314unlock:
315 spin_unlock(&output->lock);
316 spin_unlock(&stm->mc_lock);
317
318 return ret;
319}
320
321static void stm_output_free(struct stm_device *stm, struct stm_output *output)
322{
323 spin_lock(&stm->mc_lock);
324 spin_lock(&output->lock);
325 if (output->nr_chans)
326 stm_output_disclaim(stm, output);
327 spin_unlock(&output->lock);
328 spin_unlock(&stm->mc_lock);
329}
330
331static void stm_output_init(struct stm_output *output)
332{
333 spin_lock_init(&output->lock);
334}
335
336static int major_match(struct device *dev, const void *data)
337{
338 unsigned int major = *(unsigned int *)data;
339
340 return MAJOR(dev->devt) == major;
341}
342
343static int stm_char_open(struct inode *inode, struct file *file)
344{
345 struct stm_file *stmf;
346 struct device *dev;
347 unsigned int major = imajor(inode);
348 int err = -ENODEV;
349
350 dev = class_find_device(&stm_class, NULL, &major, major_match);
351 if (!dev)
352 return -ENODEV;
353
354 stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
355 if (!stmf)
356 return -ENOMEM;
357
358 stm_output_init(&stmf->output);
359 stmf->stm = to_stm_device(dev);
360
361 if (!try_module_get(stmf->stm->owner))
362 goto err_free;
363
364 file->private_data = stmf;
365
366 return nonseekable_open(inode, file);
367
368err_free:
369 /* matches class_find_device() above */
370 put_device(dev);
371 kfree(stmf);
372
373 return err;
374}
375
376static int stm_char_release(struct inode *inode, struct file *file)
377{
378 struct stm_file *stmf = file->private_data;
379 struct stm_device *stm = stmf->stm;
380
381 if (stm->data->unlink)
382 stm->data->unlink(stm->data, stmf->output.master,
383 stmf->output.channel);
384
385 stm_output_free(stm, &stmf->output);
386
387 /*
388 * matches the stm_char_open()'s
389 * class_find_device() + try_module_get()
390 */
391 stm_put_device(stm);
392 kfree(stmf);
393
394 return 0;
395}
396
397static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
398{
399 struct stm_device *stm = stmf->stm;
400 int ret;
401
402 stmf->policy_node = stp_policy_node_lookup(stm, id);
403
404 ret = stm_output_assign(stm, width, stmf->policy_node, &stmf->output);
405
406 if (stmf->policy_node)
407 stp_policy_node_put(stmf->policy_node);
408
409 return ret;
410}
411
412static ssize_t stm_write(struct stm_data *data, unsigned int master,
413 unsigned int channel, const char *buf, size_t count)
414{
415 unsigned int flags = STP_PACKET_TIMESTAMPED;
416 const unsigned char *p = buf, nil = 0;
417 size_t pos;
418 ssize_t sz;
419
420 for (pos = 0, p = buf; count > pos; pos += sz, p += sz) {
421 sz = min_t(unsigned int, count - pos, 8);
422 sz = data->packet(data, master, channel, STP_PACKET_DATA, flags,
423 sz, p);
424 flags = 0;
425
426 if (sz < 0)
427 break;
428 }
429
430 data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil);
431
432 return pos;
433}
434
435static ssize_t stm_char_write(struct file *file, const char __user *buf,
436 size_t count, loff_t *ppos)
437{
438 struct stm_file *stmf = file->private_data;
439 struct stm_device *stm = stmf->stm;
440 char *kbuf;
441 int err;
442
443 if (count + 1 > PAGE_SIZE)
444 count = PAGE_SIZE - 1;
445
446 /*
447 * if no m/c have been assigned to this writer up to this
448 * point, use "default" policy entry
449 */
450 if (!stmf->output.nr_chans) {
451 err = stm_file_assign(stmf, "default", 1);
452 /*
453 * EBUSY means that somebody else just assigned this
454 * output, which is just fine for write()
455 */
456 if (err && err != -EBUSY)
457 return err;
458 }
459
460 kbuf = kmalloc(count + 1, GFP_KERNEL);
461 if (!kbuf)
462 return -ENOMEM;
463
464 err = copy_from_user(kbuf, buf, count);
465 if (err) {
466 kfree(kbuf);
467 return -EFAULT;
468 }
469
470 count = stm_write(stm->data, stmf->output.master, stmf->output.channel,
471 kbuf, count);
472
473 kfree(kbuf);
474
475 return count;
476}
477
478static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
479{
480 struct stm_file *stmf = file->private_data;
481 struct stm_device *stm = stmf->stm;
482 unsigned long size, phys;
483
484 if (!stm->data->mmio_addr)
485 return -EOPNOTSUPP;
486
487 if (vma->vm_pgoff)
488 return -EINVAL;
489
490 size = vma->vm_end - vma->vm_start;
491
492 if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
493 return -EINVAL;
494
495 phys = stm->data->mmio_addr(stm->data, stmf->output.master,
496 stmf->output.channel,
497 stmf->output.nr_chans);
498
499 if (!phys)
500 return -EINVAL;
501
502 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
503 vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
504 vm_iomap_memory(vma, phys, size);
505
506 return 0;
507}
508
509static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
510{
511 struct stm_device *stm = stmf->stm;
512 struct stp_policy_id *id;
513 int ret = -EINVAL;
514 u32 size;
515
516 if (stmf->output.nr_chans)
517 return -EBUSY;
518
519 if (copy_from_user(&size, arg, sizeof(size)))
520 return -EFAULT;
521
522 if (size >= PATH_MAX + sizeof(*id))
523 return -EINVAL;
524
525 /*
526 * size + 1 to make sure the .id string at the bottom is terminated,
527 * which is also why memdup_user() is not useful here
528 */
529 id = kzalloc(size + 1, GFP_KERNEL);
530 if (!id)
531 return -ENOMEM;
532
533 if (copy_from_user(id, arg, size)) {
534 ret = -EFAULT;
535 goto err_free;
536 }
537
538 if (id->__reserved_0 || id->__reserved_1)
539 goto err_free;
540
541 if (id->width < 1 ||
542 id->width > PAGE_SIZE / stm->data->sw_mmiosz)
543 goto err_free;
544
545 ret = stm_file_assign(stmf, id->id, id->width);
546 if (ret)
547 goto err_free;
548
549 ret = 0;
550
551 if (stm->data->link)
552 ret = stm->data->link(stm->data, stmf->output.master,
553 stmf->output.channel);
554
555 if (ret)
556 stm_output_free(stmf->stm, &stmf->output);
557
558err_free:
559 kfree(id);
560
561 return ret;
562}
563
564static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
565{
566 struct stp_policy_id id = {
567 .size = sizeof(id),
568 .master = stmf->output.master,
569 .channel = stmf->output.channel,
570 .width = stmf->output.nr_chans,
571 .__reserved_0 = 0,
572 .__reserved_1 = 0,
573 };
574
575 return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
576}
577
578static long
579stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
580{
581 struct stm_file *stmf = file->private_data;
582 struct stm_data *stm_data = stmf->stm->data;
583 int err = -ENOTTY;
584 u64 options;
585
586 switch (cmd) {
587 case STP_POLICY_ID_SET:
588 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
589 if (err)
590 return err;
591
592 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
593
594 case STP_POLICY_ID_GET:
595 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
596
597 case STP_SET_OPTIONS:
598 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
599 return -EFAULT;
600
601 if (stm_data->set_options)
602 err = stm_data->set_options(stm_data,
603 stmf->output.master,
604 stmf->output.channel,
605 stmf->output.nr_chans,
606 options);
607
608 break;
609 default:
610 break;
611 }
612
613 return err;
614}
615
616#ifdef CONFIG_COMPAT
617static long
618stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
619{
620 return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
621}
622#else
623#define stm_char_compat_ioctl NULL
624#endif
625
626static const struct file_operations stm_fops = {
627 .open = stm_char_open,
628 .release = stm_char_release,
629 .write = stm_char_write,
630 .mmap = stm_char_mmap,
631 .unlocked_ioctl = stm_char_ioctl,
632 .compat_ioctl = stm_char_compat_ioctl,
633 .llseek = no_llseek,
634};
635
636static void stm_device_release(struct device *dev)
637{
638 struct stm_device *stm = to_stm_device(dev);
639
640 kfree(stm);
641}
642
643int stm_register_device(struct device *parent, struct stm_data *stm_data,
644 struct module *owner)
645{
646 struct stm_device *stm;
647 unsigned int nmasters;
648 int err = -ENOMEM;
649
650 if (!stm_core_up)
651 return -EPROBE_DEFER;
652
653 if (!stm_data->packet || !stm_data->sw_nchannels)
654 return -EINVAL;
655
656 nmasters = stm_data->sw_end - stm_data->sw_start + 1;
657 stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
658 if (!stm)
659 return -ENOMEM;
660
661 stm->major = register_chrdev(0, stm_data->name, &stm_fops);
662 if (stm->major < 0)
663 goto err_free;
664
665 device_initialize(&stm->dev);
666 stm->dev.devt = MKDEV(stm->major, 0);
667 stm->dev.class = &stm_class;
668 stm->dev.parent = parent;
669 stm->dev.release = stm_device_release;
670
671 err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
672 if (err)
673 goto err_device;
674
675 err = device_add(&stm->dev);
676 if (err)
677 goto err_device;
678
679 mutex_init(&stm->link_mutex);
680 spin_lock_init(&stm->link_lock);
681 INIT_LIST_HEAD(&stm->link_list);
682
683 spin_lock_init(&stm->mc_lock);
684 mutex_init(&stm->policy_mutex);
685 stm->sw_nmasters = nmasters;
686 stm->owner = owner;
687 stm->data = stm_data;
688 stm_data->stm = stm;
689
690 return 0;
691
692err_device:
693 /* matches device_initialize() above */
694 put_device(&stm->dev);
695err_free:
696 kfree(stm);
697
698 return err;
699}
700EXPORT_SYMBOL_GPL(stm_register_device);
701
702static int __stm_source_link_drop(struct stm_source_device *src,
703 struct stm_device *stm);
704
705void stm_unregister_device(struct stm_data *stm_data)
706{
707 struct stm_device *stm = stm_data->stm;
708 struct stm_source_device *src, *iter;
709 int i, ret;
710
711 mutex_lock(&stm->link_mutex);
712 list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
713 ret = __stm_source_link_drop(src, stm);
714 /*
715 * src <-> stm link must not change under the same
716 * stm::link_mutex, so complain loudly if it has;
717 * also in this situation ret!=0 means this src is
718 * not connected to this stm and it should be otherwise
719 * safe to proceed with the tear-down of stm.
720 */
721 WARN_ON_ONCE(ret);
722 }
723 mutex_unlock(&stm->link_mutex);
724
725 synchronize_srcu(&stm_source_srcu);
726
727 unregister_chrdev(stm->major, stm_data->name);
728
729 mutex_lock(&stm->policy_mutex);
730 if (stm->policy)
731 stp_policy_unbind(stm->policy);
732 mutex_unlock(&stm->policy_mutex);
733
734 for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
735 stp_master_free(stm, i);
736
737 device_unregister(&stm->dev);
738 stm_data->stm = NULL;
739}
740EXPORT_SYMBOL_GPL(stm_unregister_device);
741
742/*
743 * stm::link_list access serialization uses a spinlock and a mutex; holding
744 * either of them guarantees that the list is stable; modification requires
745 * holding both of them.
746 *
747 * Lock ordering is as follows:
748 * stm::link_mutex
749 * stm::link_lock
750 * src::link_lock
751 */
752
753/**
754 * stm_source_link_add() - connect an stm_source device to an stm device
755 * @src: stm_source device
756 * @stm: stm device
757 *
758 * This function establishes a link from stm_source to an stm device so that
759 * the former can send out trace data to the latter.
760 *
761 * Return: 0 on success, -errno otherwise.
762 */
763static int stm_source_link_add(struct stm_source_device *src,
764 struct stm_device *stm)
765{
766 char *id;
767 int err;
768
769 mutex_lock(&stm->link_mutex);
770 spin_lock(&stm->link_lock);
771 spin_lock(&src->link_lock);
772
773 /* src->link is dereferenced under stm_source_srcu but not the list */
774 rcu_assign_pointer(src->link, stm);
775 list_add_tail(&src->link_entry, &stm->link_list);
776
777 spin_unlock(&src->link_lock);
778 spin_unlock(&stm->link_lock);
779 mutex_unlock(&stm->link_mutex);
780
781 id = kstrdup(src->data->name, GFP_KERNEL);
782 if (id) {
783 src->policy_node =
784 stp_policy_node_lookup(stm, id);
785
786 kfree(id);
787 }
788
789 err = stm_output_assign(stm, src->data->nr_chans,
790 src->policy_node, &src->output);
791
792 if (src->policy_node)
793 stp_policy_node_put(src->policy_node);
794
795 if (err)
796 goto fail_detach;
797
798 /* this is to notify the STM device that a new link has been made */
799 if (stm->data->link)
800 err = stm->data->link(stm->data, src->output.master,
801 src->output.channel);
802
803 if (err)
804 goto fail_free_output;
805
806 /* this is to let the source carry out all necessary preparations */
807 if (src->data->link)
808 src->data->link(src->data);
809
810 return 0;
811
812fail_free_output:
813 stm_output_free(stm, &src->output);
814
815fail_detach:
816 mutex_lock(&stm->link_mutex);
817 spin_lock(&stm->link_lock);
818 spin_lock(&src->link_lock);
819
820 rcu_assign_pointer(src->link, NULL);
821 list_del_init(&src->link_entry);
822
823 spin_unlock(&src->link_lock);
824 spin_unlock(&stm->link_lock);
825 mutex_unlock(&stm->link_mutex);
826
827 return err;
828}
829
830/**
831 * __stm_source_link_drop() - detach stm_source from an stm device
832 * @src: stm_source device
833 * @stm: stm device
834 *
835 * If @stm is @src::link, disconnect them from one another and put the
836 * reference on the @stm device.
837 *
838 * Caller must hold stm::link_mutex.
839 */
840static int __stm_source_link_drop(struct stm_source_device *src,
841 struct stm_device *stm)
842{
843 struct stm_device *link;
844 int ret = 0;
845
846 lockdep_assert_held(&stm->link_mutex);
847
848 /* for stm::link_list modification, we hold both mutex and spinlock */
849 spin_lock(&stm->link_lock);
850 spin_lock(&src->link_lock);
851 link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
852
853 /*
854 * The linked device may have changed since we last looked, because
855 * we weren't holding the src::link_lock back then; if this is the
856 * case, tell the caller to retry.
857 */
858 if (link != stm) {
859 ret = -EAGAIN;
860 goto unlock;
861 }
862
863 stm_output_free(link, &src->output);
864 list_del_init(&src->link_entry);
865 /* matches stm_find_device() from stm_source_link_store() */
866 stm_put_device(link);
867 rcu_assign_pointer(src->link, NULL);
868
869unlock:
870 spin_unlock(&src->link_lock);
871 spin_unlock(&stm->link_lock);
872
873 /*
874 * Call the unlink callbacks for both source and stm, when we know
875 * that we have actually performed the unlinking.
876 */
877 if (!ret) {
878 if (src->data->unlink)
879 src->data->unlink(src->data);
880
881 if (stm->data->unlink)
882 stm->data->unlink(stm->data, src->output.master,
883 src->output.channel);
884 }
885
886 return ret;
887}
888
889/**
890 * stm_source_link_drop() - detach stm_source from its stm device
891 * @src: stm_source device
892 *
893 * Unlinking means disconnecting from source's STM device; after this
894 * writes will be unsuccessful until it is linked to a new STM device.
895 *
896 * This will happen on "stm_source_link" sysfs attribute write to undo
897 * the existing link (if any), or on linked STM device's de-registration.
898 */
899static void stm_source_link_drop(struct stm_source_device *src)
900{
901 struct stm_device *stm;
902 int idx, ret;
903
904retry:
905 idx = srcu_read_lock(&stm_source_srcu);
906 /*
907 * The stm device will be valid for the duration of this
908 * read section, but the link may change before we grab
909 * the src::link_lock in __stm_source_link_drop().
910 */
911 stm = srcu_dereference(src->link, &stm_source_srcu);
912
913 ret = 0;
914 if (stm) {
915 mutex_lock(&stm->link_mutex);
916 ret = __stm_source_link_drop(src, stm);
917 mutex_unlock(&stm->link_mutex);
918 }
919
920 srcu_read_unlock(&stm_source_srcu, idx);
921
922 /* if it did change, retry */
923 if (ret == -EAGAIN)
924 goto retry;
925}
926
927static ssize_t stm_source_link_show(struct device *dev,
928 struct device_attribute *attr,
929 char *buf)
930{
931 struct stm_source_device *src = to_stm_source_device(dev);
932 struct stm_device *stm;
933 int idx, ret;
934
935 idx = srcu_read_lock(&stm_source_srcu);
936 stm = srcu_dereference(src->link, &stm_source_srcu);
937 ret = sprintf(buf, "%s\n",
938 stm ? dev_name(&stm->dev) : "<none>");
939 srcu_read_unlock(&stm_source_srcu, idx);
940
941 return ret;
942}
943
944static ssize_t stm_source_link_store(struct device *dev,
945 struct device_attribute *attr,
946 const char *buf, size_t count)
947{
948 struct stm_source_device *src = to_stm_source_device(dev);
949 struct stm_device *link;
950 int err;
951
952 stm_source_link_drop(src);
953
954 link = stm_find_device(buf);
955 if (!link)
956 return -EINVAL;
957
958 err = stm_source_link_add(src, link);
959 if (err) {
960 /* matches the stm_find_device() above */
961 stm_put_device(link);
962 }
963
964 return err ? : count;
965}
966
967static DEVICE_ATTR_RW(stm_source_link);
968
969static struct attribute *stm_source_attrs[] = {
970 &dev_attr_stm_source_link.attr,
971 NULL,
972};
973
974ATTRIBUTE_GROUPS(stm_source);
975
976static struct class stm_source_class = {
977 .name = "stm_source",
978 .dev_groups = stm_source_groups,
979};
980
981static void stm_source_device_release(struct device *dev)
982{
983 struct stm_source_device *src = to_stm_source_device(dev);
984
985 kfree(src);
986}
987
988/**
989 * stm_source_register_device() - register an stm_source device
990 * @parent: parent device
991 * @data: device description structure
992 *
993 * This will create a device of stm_source class that can write
994 * data to an stm device once linked.
995 *
996 * Return: 0 on success, -errno otherwise.
997 */
998int stm_source_register_device(struct device *parent,
999 struct stm_source_data *data)
1000{
1001 struct stm_source_device *src;
1002 int err;
1003
1004 if (!stm_core_up)
1005 return -EPROBE_DEFER;
1006
1007 src = kzalloc(sizeof(*src), GFP_KERNEL);
1008 if (!src)
1009 return -ENOMEM;
1010
1011 device_initialize(&src->dev);
1012 src->dev.class = &stm_source_class;
1013 src->dev.parent = parent;
1014 src->dev.release = stm_source_device_release;
1015
1016 err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1017 if (err)
1018 goto err;
1019
1020 err = device_add(&src->dev);
1021 if (err)
1022 goto err;
1023
1024 stm_output_init(&src->output);
1025 spin_lock_init(&src->link_lock);
1026 INIT_LIST_HEAD(&src->link_entry);
1027 src->data = data;
1028 data->src = src;
1029
1030 return 0;
1031
1032err:
1033 put_device(&src->dev);
1034 kfree(src);
1035
1036 return err;
1037}
1038EXPORT_SYMBOL_GPL(stm_source_register_device);
1039
1040/**
1041 * stm_source_unregister_device() - unregister an stm_source device
1042 * @data: device description that was used to register the device
1043 *
1044 * This will remove a previously created stm_source device from the system.
1045 */
1046void stm_source_unregister_device(struct stm_source_data *data)
1047{
1048 struct stm_source_device *src = data->src;
1049
1050 stm_source_link_drop(src);
1051
1052 device_destroy(&stm_source_class, src->dev.devt);
1053}
1054EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1055
1056int stm_source_write(struct stm_source_data *data, unsigned int chan,
1057 const char *buf, size_t count)
1058{
1059 struct stm_source_device *src = data->src;
1060 struct stm_device *stm;
1061 int idx;
1062
1063 if (!src->output.nr_chans)
1064 return -ENODEV;
1065
1066 if (chan >= src->output.nr_chans)
1067 return -EINVAL;
1068
1069 idx = srcu_read_lock(&stm_source_srcu);
1070
1071 stm = srcu_dereference(src->link, &stm_source_srcu);
1072 if (stm)
1073 count = stm_write(stm->data, src->output.master,
1074 src->output.channel + chan,
1075 buf, count);
1076 else
1077 count = -ENODEV;
1078
1079 srcu_read_unlock(&stm_source_srcu, idx);
1080
1081 return count;
1082}
1083EXPORT_SYMBOL_GPL(stm_source_write);
1084
1085static int __init stm_core_init(void)
1086{
1087 int err;
1088
1089 err = class_register(&stm_class);
1090 if (err)
1091 return err;
1092
1093 err = class_register(&stm_source_class);
1094 if (err)
1095 goto err_stm;
1096
1097 err = stp_configfs_init();
1098 if (err)
1099 goto err_src;
1100
1101 init_srcu_struct(&stm_source_srcu);
1102
1103 stm_core_up++;
1104
1105 return 0;
1106
1107err_src:
1108 class_unregister(&stm_source_class);
1109err_stm:
1110 class_unregister(&stm_class);
1111
1112 return err;
1113}
1114
1115module_init(stm_core_init);
1116
1117static void __exit stm_core_exit(void)
1118{
1119 cleanup_srcu_struct(&stm_source_srcu);
1120 class_unregister(&stm_source_class);
1121 class_unregister(&stm_class);
1122 stp_configfs_exit();
1123}
1124
1125module_exit(stm_core_exit);
1126
1127MODULE_LICENSE("GPL v2");
1128MODULE_DESCRIPTION("System Trace Module device class");
1129MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");