drivers/hwtracing/stm/core.c

   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
  33 static 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  */
  40 static struct srcu_struct stm_source_srcu;
  41
  42 static 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
  54 static DEVICE_ATTR_RO(masters);
  55
  56 static 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
  68 static DEVICE_ATTR_RO(channels);
  69
  70 static ssize_t hw_override_show(struct device *dev,
  71                                 struct device_attribute *attr,
  72                                 char *buf)
  73 {
  74         struct stm_device *stm = to_stm_device(dev);
  75         int ret;
  76
  77         ret = sprintf(buf, "%u\n", stm->data->hw_override);
  78
  79         return ret;
  80 }
  81
  82 static DEVICE_ATTR_RO(hw_override);
  83
  84 static struct attribute *stm_attrs[] = {
  85         &dev_attr_masters.attr,
  86         &dev_attr_channels.attr,
  87         &dev_attr_hw_override.attr,
  88         NULL,
  89 };
  90
  91 ATTRIBUTE_GROUPS(stm);
  92
  93 static struct class stm_class = {
  94         .name           = "stm",
  95         .dev_groups     = stm_groups,
  96 };
  97
  98 static int stm_dev_match(struct device *dev, const void *data)
  99 {
 100         const char *name = data;
 101
 102         return sysfs_streq(name, dev_name(dev));
 103 }
 104
 105 /**
 106  * stm_find_device() - find stm device by name
 107  * @buf:        character buffer containing the name
 108  *
 109  * This is called when either policy gets assigned to an stm device or an
 110  * stm_source device gets linked to an stm device.
 111  *
 112  * This grabs device's reference (get_device()) and module reference, both
 113  * of which the calling path needs to make sure to drop with stm_put_device().
 114  *
 115  * Return:      stm device pointer or null if lookup failed.
 116  */
 117 struct stm_device *stm_find_device(const char *buf)
 118 {
 119         struct stm_device *stm;
 120         struct device *dev;
 121
 122         if (!stm_core_up)
 123                 return NULL;
 124
 125         dev = class_find_device(&stm_class, NULL, buf, stm_dev_match);
 126         if (!dev)
 127                 return NULL;
 128
 129         stm = to_stm_device(dev);
 130         if (!try_module_get(stm->owner)) {
 131                 /* matches class_find_device() above */
 132                 put_device(dev);
 133                 return NULL;
 134         }
 135
 136         return stm;
 137 }
 138
 139 /**
 140  * stm_put_device() - drop references on the stm device
 141  * @stm:        stm device, previously acquired by stm_find_device()
 142  *
 143  * This drops the module reference and device reference taken by
 144  * stm_find_device() or stm_char_open().
 145  */
 146 void stm_put_device(struct stm_device *stm)
 147 {
 148         module_put(stm->owner);
 149         put_device(&stm->dev);
 150 }
 151
 152 /*
 153  * Internally we only care about software-writable masters here, that is the
 154  * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
 155  * original master numbers to be visible externally, since they are the ones
 156  * that will appear in the STP stream. Thus, the internal bookkeeping uses
 157  * $master - stm_data->sw_start to reference master descriptors and such.
 158  */
 159
 160 #define __stm_master(_s, _m)                            \
 161         ((_s)->masters[(_m) - (_s)->data->sw_start])
 162
 163 static inline struct stp_master *
 164 stm_master(struct stm_device *stm, unsigned int idx)
 165 {
 166         if (idx < stm->data->sw_start || idx > stm->data->sw_end)
 167                 return NULL;
 168
 169         return __stm_master(stm, idx);
 170 }
 171
 172 static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
 173 {
 174         struct stp_master *master;
 175         size_t size;
 176
 177         size = ALIGN(stm->data->sw_nchannels, 8) / 8;
 178         size += sizeof(struct stp_master);
 179         master = kzalloc(size, GFP_ATOMIC);
 180         if (!master)
 181                 return -ENOMEM;
 182
 183         master->nr_free = stm->data->sw_nchannels;
 184         __stm_master(stm, idx) = master;
 185
 186         return 0;
 187 }
 188
 189 static void stp_master_free(struct stm_device *stm, unsigned int idx)
 190 {
 191         struct stp_master *master = stm_master(stm, idx);
 192
 193         if (!master)
 194                 return;
 195
 196         __stm_master(stm, idx) = NULL;
 197         kfree(master);
 198 }
 199
 200 static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
 201 {
 202         struct stp_master *master = stm_master(stm, output->master);
 203
 204         lockdep_assert_held(&stm->mc_lock);
 205         lockdep_assert_held(&output->lock);
 206
 207         if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
 208                 return;
 209
 210         bitmap_allocate_region(&master->chan_map[0], output->channel,
 211                                ilog2(output->nr_chans));
 212
 213         master->nr_free -= output->nr_chans;
 214 }
 215
 216 static void
 217 stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
 218 {
 219         struct stp_master *master = stm_master(stm, output->master);
 220
 221         lockdep_assert_held(&stm->mc_lock);
 222         lockdep_assert_held(&output->lock);
 223
 224         bitmap_release_region(&master->chan_map[0], output->channel,
 225                               ilog2(output->nr_chans));
 226
 227         output->nr_chans = 0;
 228         master->nr_free += output->nr_chans;
 229 }
 230
 231 /*
 232  * This is like bitmap_find_free_region(), except it can ignore @start bits
 233  * at the beginning.
 234  */
 235 static int find_free_channels(unsigned long *bitmap, unsigned int start,
 236                               unsigned int end, unsigned int width)
 237 {
 238         unsigned int pos;
 239         int i;
 240
 241         for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
 242                 pos = find_next_zero_bit(bitmap, end + 1, pos);
 243                 if (pos + width > end + 1)
 244                         break;
 245
 246                 if (pos & (width - 1))
 247                         continue;
 248
 249                 for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
 250                         ;
 251                 if (i == width)
 252                         return pos;
 253         }
 254
 255         return -1;
 256 }
 257
 258 static int
 259 stm_find_master_chan(struct stm_device *stm, unsigned int width,
 260                      unsigned int *mstart, unsigned int mend,
 261                      unsigned int *cstart, unsigned int cend)
 262 {
 263         struct stp_master *master;
 264         unsigned int midx;
 265         int pos, err;
 266
 267         for (midx = *mstart; midx <= mend; midx++) {
 268                 if (!stm_master(stm, midx)) {
 269                         err = stp_master_alloc(stm, midx);
 270                         if (err)
 271                                 return err;
 272                 }
 273
 274                 master = stm_master(stm, midx);
 275
 276                 if (!master->nr_free)
 277                         continue;
 278
 279                 pos = find_free_channels(master->chan_map, *cstart, cend,
 280                                          width);
 281                 if (pos < 0)
 282                         continue;
 283
 284                 *mstart = midx;
 285                 *cstart = pos;
 286                 return 0;
 287         }
 288
 289         return -ENOSPC;
 290 }
 291
 292 static int stm_output_assign(struct stm_device *stm, unsigned int width,
 293                              struct stp_policy_node *policy_node,
 294                              struct stm_output *output)
 295 {
 296         unsigned int midx, cidx, mend, cend;
 297         int ret = -EINVAL;
 298
 299         if (width > stm->data->sw_nchannels)
 300                 return -EINVAL;
 301
 302         if (policy_node) {
 303                 stp_policy_node_get_ranges(policy_node,
 304                                            &midx, &mend, &cidx, &cend);
 305         } else {
 306                 midx = stm->data->sw_start;
 307                 cidx = 0;
 308                 mend = stm->data->sw_end;
 309                 cend = stm->data->sw_nchannels - 1;
 310         }
 311
 312         spin_lock(&stm->mc_lock);
 313         spin_lock(&output->lock);
 314         /* output is already assigned -- shouldn't happen */
 315         if (WARN_ON_ONCE(output->nr_chans))
 316                 goto unlock;
 317
 318         ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
 319         if (ret < 0)
 320                 goto unlock;
 321
 322         output->master = midx;
 323         output->channel = cidx;
 324         output->nr_chans = width;
 325         stm_output_claim(stm, output);
 326         dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);
 327
 328         ret = 0;
 329 unlock:
 330         spin_unlock(&output->lock);
 331         spin_unlock(&stm->mc_lock);
 332
 333         return ret;
 334 }
 335
 336 static void stm_output_free(struct stm_device *stm, struct stm_output *output)
 337 {
 338         spin_lock(&stm->mc_lock);
 339         spin_lock(&output->lock);
 340         if (output->nr_chans)
 341                 stm_output_disclaim(stm, output);
 342         spin_unlock(&output->lock);
 343         spin_unlock(&stm->mc_lock);
 344 }
 345
 346 static void stm_output_init(struct stm_output *output)
 347 {
 348         spin_lock_init(&output->lock);
 349 }
 350
 351 static int major_match(struct device *dev, const void *data)
 352 {
 353         unsigned int major = *(unsigned int *)data;
 354
 355         return MAJOR(dev->devt) == major;
 356 }
 357
 358 static int stm_char_open(struct inode *inode, struct file *file)
 359 {
 360         struct stm_file *stmf;
 361         struct device *dev;
 362         unsigned int major = imajor(inode);
 363         int err = -ENODEV;
 364
 365         dev = class_find_device(&stm_class, NULL, &major, major_match);
 366         if (!dev)
 367                 return -ENODEV;
 368
 369         stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
 370         if (!stmf)
 371                 return -ENOMEM;
 372
 373         stm_output_init(&stmf->output);
 374         stmf->stm = to_stm_device(dev);
 375
 376         if (!try_module_get(stmf->stm->owner))
 377                 goto err_free;
 378
 379         file->private_data = stmf;
 380
 381         return nonseekable_open(inode, file);
 382
 383 err_free:
 384         /* matches class_find_device() above */
 385         put_device(dev);
 386         kfree(stmf);
 387
 388         return err;
 389 }
 390
 391 static int stm_char_release(struct inode *inode, struct file *file)
 392 {
 393         struct stm_file *stmf = file->private_data;
 394         struct stm_device *stm = stmf->stm;
 395
 396         if (stm->data->unlink)
 397                 stm->data->unlink(stm->data, stmf->output.master,
 398                                   stmf->output.channel);
 399
 400         stm_output_free(stm, &stmf->output);
 401
 402         /*
 403          * matches the stm_char_open()'s
 404          * class_find_device() + try_module_get()
 405          */
 406         stm_put_device(stm);
 407         kfree(stmf);
 408
 409         return 0;
 410 }
 411
 412 static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
 413 {
 414         struct stm_device *stm = stmf->stm;
 415         int ret;
 416
 417         stmf->policy_node = stp_policy_node_lookup(stm, id);
 418
 419         ret = stm_output_assign(stm, width, stmf->policy_node, &stmf->output);
 420
 421         if (stmf->policy_node)
 422                 stp_policy_node_put(stmf->policy_node);
 423
 424         return ret;
 425 }
 426
 427 static ssize_t stm_write(struct stm_data *data, unsigned int master,
 428                           unsigned int channel, const char *buf, size_t count)
 429 {
 430         unsigned int flags = STP_PACKET_TIMESTAMPED;
 431         const unsigned char *p = buf, nil = 0;
 432         size_t pos;
 433         ssize_t sz;
 434
 435         for (pos = 0, p = buf; count > pos; pos += sz, p += sz) {
 436                 sz = min_t(unsigned int, count - pos, 8);
 437                 sz = data->packet(data, master, channel, STP_PACKET_DATA, flags,
 438                                   sz, p);
 439                 flags = 0;
 440
 441                 if (sz < 0)
 442                         break;
 443         }
 444
 445         data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil);
 446
 447         return pos;
 448 }
 449
 450 static ssize_t stm_char_write(struct file *file, const char __user *buf,
 451                               size_t count, loff_t *ppos)
 452 {
 453         struct stm_file *stmf = file->private_data;
 454         struct stm_device *stm = stmf->stm;
 455         char *kbuf;
 456         int err;
 457
 458         if (count + 1 > PAGE_SIZE)
 459                 count = PAGE_SIZE - 1;
 460
 461         /*
 462          * if no m/c have been assigned to this writer up to this
 463          * point, use "default" policy entry
 464          */
 465         if (!stmf->output.nr_chans) {
 466                 err = stm_file_assign(stmf, "default", 1);
 467                 /*
 468                  * EBUSY means that somebody else just assigned this
 469                  * output, which is just fine for write()
 470                  */
 471                 if (err && err != -EBUSY)
 472                         return err;
 473         }
 474
 475         kbuf = kmalloc(count + 1, GFP_KERNEL);
 476         if (!kbuf)
 477                 return -ENOMEM;
 478
 479         err = copy_from_user(kbuf, buf, count);
 480         if (err) {
 481                 kfree(kbuf);
 482                 return -EFAULT;
 483         }
 484
 485         count = stm_write(stm->data, stmf->output.master, stmf->output.channel,
 486                           kbuf, count);
 487
 488         kfree(kbuf);
 489
 490         return count;
 491 }
 492
 493 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 494 {
 495         struct stm_file *stmf = file->private_data;
 496         struct stm_device *stm = stmf->stm;
 497         unsigned long size, phys;
 498
 499         if (!stm->data->mmio_addr)
 500                 return -EOPNOTSUPP;
 501
 502         if (vma->vm_pgoff)
 503                 return -EINVAL;
 504
 505         size = vma->vm_end - vma->vm_start;
 506
 507         if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
 508                 return -EINVAL;
 509
 510         phys = stm->data->mmio_addr(stm->data, stmf->output.master,
 511                                     stmf->output.channel,
 512                                     stmf->output.nr_chans);
 513
 514         if (!phys)
 515                 return -EINVAL;
 516
 517         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 518         vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
 519         vm_iomap_memory(vma, phys, size);
 520
 521         return 0;
 522 }
 523
 524 static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 525 {
 526         struct stm_device *stm = stmf->stm;
 527         struct stp_policy_id *id;
 528         int ret = -EINVAL;
 529         u32 size;
 530
 531         if (stmf->output.nr_chans)
 532                 return -EBUSY;
 533
 534         if (copy_from_user(&size, arg, sizeof(size)))
 535                 return -EFAULT;
 536
 537         if (size >= PATH_MAX + sizeof(*id))
 538                 return -EINVAL;
 539
 540         /*
 541          * size + 1 to make sure the .id string at the bottom is terminated,
 542          * which is also why memdup_user() is not useful here
 543          */
 544         id = kzalloc(size + 1, GFP_KERNEL);
 545         if (!id)
 546                 return -ENOMEM;
 547
 548         if (copy_from_user(id, arg, size)) {
 549                 ret = -EFAULT;
 550                 goto err_free;
 551         }
 552
 553         if (id->__reserved_0 || id->__reserved_1)
 554                 goto err_free;
 555
 556         if (id->width < 1 ||
 557             id->width > PAGE_SIZE / stm->data->sw_mmiosz)
 558                 goto err_free;
 559
 560         ret = stm_file_assign(stmf, id->id, id->width);
 561         if (ret)
 562                 goto err_free;
 563
 564         if (stm->data->link)
 565                 ret = stm->data->link(stm->data, stmf->output.master,
 566                                       stmf->output.channel);
 567
 568         if (ret)
 569                 stm_output_free(stmf->stm, &stmf->output);
 570
 571 err_free:
 572         kfree(id);
 573
 574         return ret;
 575 }
 576
 577 static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
 578 {
 579         struct stp_policy_id id = {
 580                 .size           = sizeof(id),
 581                 .master         = stmf->output.master,
 582                 .channel        = stmf->output.channel,
 583                 .width          = stmf->output.nr_chans,
 584                 .__reserved_0   = 0,
 585                 .__reserved_1   = 0,
 586         };
 587
 588         return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
 589 }
 590
 591 static long
 592 stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 593 {
 594         struct stm_file *stmf = file->private_data;
 595         struct stm_data *stm_data = stmf->stm->data;
 596         int err = -ENOTTY;
 597         u64 options;
 598
 599         switch (cmd) {
 600         case STP_POLICY_ID_SET:
 601                 err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
 602                 if (err)
 603                         return err;
 604
 605                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 606
 607         case STP_POLICY_ID_GET:
 608                 return stm_char_policy_get_ioctl(stmf, (void __user *)arg);
 609
 610         case STP_SET_OPTIONS:
 611                 if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
 612                         return -EFAULT;
 613
 614                 if (stm_data->set_options)
 615                         err = stm_data->set_options(stm_data,
 616                                                     stmf->output.master,
 617                                                     stmf->output.channel,
 618                                                     stmf->output.nr_chans,
 619                                                     options);
 620
 621                 break;
 622         default:
 623                 break;
 624         }
 625
 626         return err;
 627 }
 628
 629 #ifdef CONFIG_COMPAT
 630 static long
 631 stm_char_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 632 {
 633         return stm_char_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
 634 }
 635 #else
 636 #define stm_char_compat_ioctl   NULL
 637 #endif
 638
 639 static const struct file_operations stm_fops = {
 640         .open           = stm_char_open,
 641         .release        = stm_char_release,
 642         .write          = stm_char_write,
 643         .mmap           = stm_char_mmap,
 644         .unlocked_ioctl = stm_char_ioctl,
 645         .compat_ioctl   = stm_char_compat_ioctl,
 646         .llseek         = no_llseek,
 647 };
 648
 649 static void stm_device_release(struct device *dev)
 650 {
 651         struct stm_device *stm = to_stm_device(dev);
 652
 653         kfree(stm);
 654 }
 655
 656 int stm_register_device(struct device *parent, struct stm_data *stm_data,
 657                         struct module *owner)
 658 {
 659         struct stm_device *stm;
 660         unsigned int nmasters;
 661         int err = -ENOMEM;
 662
 663         if (!stm_core_up)
 664                 return -EPROBE_DEFER;
 665
 666         if (!stm_data->packet || !stm_data->sw_nchannels)
 667                 return -EINVAL;
 668
 669         nmasters = stm_data->sw_end - stm_data->sw_start + 1;
 670         stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
 671         if (!stm)
 672                 return -ENOMEM;
 673
 674         stm->major = register_chrdev(0, stm_data->name, &stm_fops);
 675         if (stm->major < 0)
 676                 goto err_free;
 677
 678         device_initialize(&stm->dev);
 679         stm->dev.devt = MKDEV(stm->major, 0);
 680         stm->dev.class = &stm_class;
 681         stm->dev.parent = parent;
 682         stm->dev.release = stm_device_release;
 683
 684         mutex_init(&stm->link_mutex);
 685         spin_lock_init(&stm->link_lock);
 686         INIT_LIST_HEAD(&stm->link_list);
 687
 688         /* initialize the object before it is accessible via sysfs */
 689         spin_lock_init(&stm->mc_lock);
 690         mutex_init(&stm->policy_mutex);
 691         stm->sw_nmasters = nmasters;
 692         stm->owner = owner;
 693         stm->data = stm_data;
 694         stm_data->stm = stm;
 695
 696         err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
 697         if (err)
 698                 goto err_device;
 699
 700         err = device_add(&stm->dev);
 701         if (err)
 702                 goto err_device;
 703
 704         return 0;
 705
 706 err_device:
 707         unregister_chrdev(stm->major, stm_data->name);
 708
 709         /* matches device_initialize() above */
 710         put_device(&stm->dev);
 711 err_free:
 712         kfree(stm);
 713
 714         return err;
 715 }
 716 EXPORT_SYMBOL_GPL(stm_register_device);
 717
 718 static int __stm_source_link_drop(struct stm_source_device *src,
 719                                   struct stm_device *stm);
 720
 721 void stm_unregister_device(struct stm_data *stm_data)
 722 {
 723         struct stm_device *stm = stm_data->stm;
 724         struct stm_source_device *src, *iter;
 725         int i, ret;
 726
 727         mutex_lock(&stm->link_mutex);
 728         list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
 729                 ret = __stm_source_link_drop(src, stm);
 730                 /*
 731                  * src <-> stm link must not change under the same
 732                  * stm::link_mutex, so complain loudly if it has;
 733                  * also in this situation ret!=0 means this src is
 734                  * not connected to this stm and it should be otherwise
 735                  * safe to proceed with the tear-down of stm.
 736                  */
 737                 WARN_ON_ONCE(ret);
 738         }
 739         mutex_unlock(&stm->link_mutex);
 740
 741         synchronize_srcu(&stm_source_srcu);
 742
 743         unregister_chrdev(stm->major, stm_data->name);
 744
 745         mutex_lock(&stm->policy_mutex);
 746         if (stm->policy)
 747                 stp_policy_unbind(stm->policy);
 748         mutex_unlock(&stm->policy_mutex);
 749
 750         for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
 751                 stp_master_free(stm, i);
 752
 753         device_unregister(&stm->dev);
 754         stm_data->stm = NULL;
 755 }
 756 EXPORT_SYMBOL_GPL(stm_unregister_device);
 757
 758 /*
 759  * stm::link_list access serialization uses a spinlock and a mutex; holding
 760  * either of them guarantees that the list is stable; modification requires
 761  * holding both of them.
 762  *
 763  * Lock ordering is as follows:
 764  *   stm::link_mutex
 765  *     stm::link_lock
 766  *       src::link_lock
 767  */
 768
 769 /**
 770  * stm_source_link_add() - connect an stm_source device to an stm device
 771  * @src:        stm_source device
 772  * @stm:        stm device
 773  *
 774  * This function establishes a link from stm_source to an stm device so that
 775  * the former can send out trace data to the latter.
 776  *
 777  * Return:      0 on success, -errno otherwise.
 778  */
 779 static int stm_source_link_add(struct stm_source_device *src,
 780                                struct stm_device *stm)
 781 {
 782         char *id;
 783         int err;
 784
 785         mutex_lock(&stm->link_mutex);
 786         spin_lock(&stm->link_lock);
 787         spin_lock(&src->link_lock);
 788
 789         /* src->link is dereferenced under stm_source_srcu but not the list */
 790         rcu_assign_pointer(src->link, stm);
 791         list_add_tail(&src->link_entry, &stm->link_list);
 792
 793         spin_unlock(&src->link_lock);
 794         spin_unlock(&stm->link_lock);
 795         mutex_unlock(&stm->link_mutex);
 796
 797         id = kstrdup(src->data->name, GFP_KERNEL);
 798         if (id) {
 799                 src->policy_node =
 800                         stp_policy_node_lookup(stm, id);
 801
 802                 kfree(id);
 803         }
 804
 805         err = stm_output_assign(stm, src->data->nr_chans,
 806                                 src->policy_node, &src->output);
 807
 808         if (src->policy_node)
 809                 stp_policy_node_put(src->policy_node);
 810
 811         if (err)
 812                 goto fail_detach;
 813
 814         /* this is to notify the STM device that a new link has been made */
 815         if (stm->data->link)
 816                 err = stm->data->link(stm->data, src->output.master,
 817                                       src->output.channel);
 818
 819         if (err)
 820                 goto fail_free_output;
 821
 822         /* this is to let the source carry out all necessary preparations */
 823         if (src->data->link)
 824                 src->data->link(src->data);
 825
 826         return 0;
 827
 828 fail_free_output:
 829         stm_output_free(stm, &src->output);
 830
 831 fail_detach:
 832         mutex_lock(&stm->link_mutex);
 833         spin_lock(&stm->link_lock);
 834         spin_lock(&src->link_lock);
 835
 836         rcu_assign_pointer(src->link, NULL);
 837         list_del_init(&src->link_entry);
 838
 839         spin_unlock(&src->link_lock);
 840         spin_unlock(&stm->link_lock);
 841         mutex_unlock(&stm->link_mutex);
 842
 843         return err;
 844 }
 845
 846 /**
 847  * __stm_source_link_drop() - detach stm_source from an stm device
 848  * @src:        stm_source device
 849  * @stm:        stm device
 850  *
 851  * If @stm is @src::link, disconnect them from one another and put the
 852  * reference on the @stm device.
 853  *
 854  * Caller must hold stm::link_mutex.
 855  */
 856 static int __stm_source_link_drop(struct stm_source_device *src,
 857                                   struct stm_device *stm)
 858 {
 859         struct stm_device *link;
 860         int ret = 0;
 861
 862         lockdep_assert_held(&stm->link_mutex);
 863
 864         /* for stm::link_list modification, we hold both mutex and spinlock */
 865         spin_lock(&stm->link_lock);
 866         spin_lock(&src->link_lock);
 867         link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
 868
 869         /*
 870          * The linked device may have changed since we last looked, because
 871          * we weren't holding the src::link_lock back then; if this is the
 872          * case, tell the caller to retry.
 873          */
 874         if (link != stm) {
 875                 ret = -EAGAIN;
 876                 goto unlock;
 877         }
 878
 879         stm_output_free(link, &src->output);
 880         list_del_init(&src->link_entry);
 881         /* matches stm_find_device() from stm_source_link_store() */
 882         stm_put_device(link);
 883         rcu_assign_pointer(src->link, NULL);
 884
 885 unlock:
 886         spin_unlock(&src->link_lock);
 887         spin_unlock(&stm->link_lock);
 888
 889         /*
 890          * Call the unlink callbacks for both source and stm, when we know
 891          * that we have actually performed the unlinking.
 892          */
 893         if (!ret) {
 894                 if (src->data->unlink)
 895                         src->data->unlink(src->data);
 896
 897                 if (stm->data->unlink)
 898                         stm->data->unlink(stm->data, src->output.master,
 899                                           src->output.channel);
 900         }
 901
 902         return ret;
 903 }
 904
 905 /**
 906  * stm_source_link_drop() - detach stm_source from its stm device
 907  * @src:        stm_source device
 908  *
 909  * Unlinking means disconnecting from source's STM device; after this
 910  * writes will be unsuccessful until it is linked to a new STM device.
 911  *
 912  * This will happen on "stm_source_link" sysfs attribute write to undo
 913  * the existing link (if any), or on linked STM device's de-registration.
 914  */
 915 static void stm_source_link_drop(struct stm_source_device *src)
 916 {
 917         struct stm_device *stm;
 918         int idx, ret;
 919
 920 retry:
 921         idx = srcu_read_lock(&stm_source_srcu);
 922         /*
 923          * The stm device will be valid for the duration of this
 924          * read section, but the link may change before we grab
 925          * the src::link_lock in __stm_source_link_drop().
 926          */
 927         stm = srcu_dereference(src->link, &stm_source_srcu);
 928
 929         ret = 0;
 930         if (stm) {
 931                 mutex_lock(&stm->link_mutex);
 932                 ret = __stm_source_link_drop(src, stm);
 933                 mutex_unlock(&stm->link_mutex);
 934         }
 935
 936         srcu_read_unlock(&stm_source_srcu, idx);
 937
 938         /* if it did change, retry */
 939         if (ret == -EAGAIN)
 940                 goto retry;
 941 }
 942
 943 static ssize_t stm_source_link_show(struct device *dev,
 944                                     struct device_attribute *attr,
 945                                     char *buf)
 946 {
 947         struct stm_source_device *src = to_stm_source_device(dev);
 948         struct stm_device *stm;
 949         int idx, ret;
 950
 951         idx = srcu_read_lock(&stm_source_srcu);
 952         stm = srcu_dereference(src->link, &stm_source_srcu);
 953         ret = sprintf(buf, "%s\n",
 954                       stm ? dev_name(&stm->dev) : "<none>");
 955         srcu_read_unlock(&stm_source_srcu, idx);
 956
 957         return ret;
 958 }
 959
 960 static ssize_t stm_source_link_store(struct device *dev,
 961                                      struct device_attribute *attr,
 962                                      const char *buf, size_t count)
 963 {
 964         struct stm_source_device *src = to_stm_source_device(dev);
 965         struct stm_device *link;
 966         int err;
 967
 968         stm_source_link_drop(src);
 969
 970         link = stm_find_device(buf);
 971         if (!link)
 972                 return -EINVAL;
 973
 974         err = stm_source_link_add(src, link);
 975         if (err) {
 976                 /* matches the stm_find_device() above */
 977                 stm_put_device(link);
 978         }
 979
 980         return err ? : count;
 981 }
 982
 983 static DEVICE_ATTR_RW(stm_source_link);
 984
 985 static struct attribute *stm_source_attrs[] = {
 986         &dev_attr_stm_source_link.attr,
 987         NULL,
 988 };
 989
 990 ATTRIBUTE_GROUPS(stm_source);
 991
 992 static struct class stm_source_class = {
 993         .name           = "stm_source",
 994         .dev_groups     = stm_source_groups,
 995 };
 996
 997 static void stm_source_device_release(struct device *dev)
 998 {
 999         struct stm_source_device *src = to_stm_source_device(dev);
1000
1001         kfree(src);
1002 }
1003
1004 /**
1005  * stm_source_register_device() - register an stm_source device
1006  * @parent:     parent device
1007  * @data:       device description structure
1008  *
1009  * This will create a device of stm_source class that can write
1010  * data to an stm device once linked.
1011  *
1012  * Return:      0 on success, -errno otherwise.
1013  */
1014 int stm_source_register_device(struct device *parent,
1015                                struct stm_source_data *data)
1016 {
1017         struct stm_source_device *src;
1018         int err;
1019
1020         if (!stm_core_up)
1021                 return -EPROBE_DEFER;
1022
1023         src = kzalloc(sizeof(*src), GFP_KERNEL);
1024         if (!src)
1025                 return -ENOMEM;
1026
1027         device_initialize(&src->dev);
1028         src->dev.class = &stm_source_class;
1029         src->dev.parent = parent;
1030         src->dev.release = stm_source_device_release;
1031
1032         err = kobject_set_name(&src->dev.kobj, "%s", data->name);
1033         if (err)
1034                 goto err;
1035
1036         err = device_add(&src->dev);
1037         if (err)
1038                 goto err;
1039
1040         stm_output_init(&src->output);
1041         spin_lock_init(&src->link_lock);
1042         INIT_LIST_HEAD(&src->link_entry);
1043         src->data = data;
1044         data->src = src;
1045
1046         return 0;
1047
1048 err:
1049         put_device(&src->dev);
1050         kfree(src);
1051
1052         return err;
1053 }
1054 EXPORT_SYMBOL_GPL(stm_source_register_device);
1055
1056 /**
1057  * stm_source_unregister_device() - unregister an stm_source device
1058  * @data:       device description that was used to register the device
1059  *
1060  * This will remove a previously created stm_source device from the system.
1061  */
1062 void stm_source_unregister_device(struct stm_source_data *data)
1063 {
1064         struct stm_source_device *src = data->src;
1065
1066         stm_source_link_drop(src);
1067
1068         device_destroy(&stm_source_class, src->dev.devt);
1069 }
1070 EXPORT_SYMBOL_GPL(stm_source_unregister_device);
1071
1072 int stm_source_write(struct stm_source_data *data, unsigned int chan,
1073                      const char *buf, size_t count)
1074 {
1075         struct stm_source_device *src = data->src;
1076         struct stm_device *stm;
1077         int idx;
1078
1079         if (!src->output.nr_chans)
1080                 return -ENODEV;
1081
1082         if (chan >= src->output.nr_chans)
1083                 return -EINVAL;
1084
1085         idx = srcu_read_lock(&stm_source_srcu);
1086
1087         stm = srcu_dereference(src->link, &stm_source_srcu);
1088         if (stm)
1089                 count = stm_write(stm->data, src->output.master,
1090                                   src->output.channel + chan,
1091                                   buf, count);
1092         else
1093                 count = -ENODEV;
1094
1095         srcu_read_unlock(&stm_source_srcu, idx);
1096
1097         return count;
1098 }
1099 EXPORT_SYMBOL_GPL(stm_source_write);
1100
1101 static int __init stm_core_init(void)
1102 {
1103         int err;
1104
1105         err = class_register(&stm_class);
1106         if (err)
1107                 return err;
1108
1109         err = class_register(&stm_source_class);
1110         if (err)
1111                 goto err_stm;
1112
1113         err = stp_configfs_init();
1114         if (err)
1115                 goto err_src;
1116
1117         init_srcu_struct(&stm_source_srcu);
1118
1119         stm_core_up++;
1120
1121         return 0;
1122
1123 err_src:
1124         class_unregister(&stm_source_class);
1125 err_stm:
1126         class_unregister(&stm_class);
1127
1128         return err;
1129 }
1130
1131 module_init(stm_core_init);
1132
1133 static void __exit stm_core_exit(void)
1134 {
1135         cleanup_srcu_struct(&stm_source_srcu);
1136         class_unregister(&stm_source_class);
1137         class_unregister(&stm_class);
1138         stp_configfs_exit();
1139 }
1140
1141 module_exit(stm_core_exit);
1142
1143 MODULE_LICENSE("GPL v2");
1144 MODULE_DESCRIPTION("System Trace Module device class");
1145 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");