1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */ 3 4 #include <linux/err.h> 5 #include <linux/errno.h> 6 #include <linux/fs.h> 7 #include <linux/init.h> 8 #include <linux/idr.h> 9 #include <linux/kernel.h> 10 #include <linux/module.h> 11 #include <linux/poll.h> 12 #include <linux/skbuff.h> 13 #include <linux/slab.h> 14 #include <linux/types.h> 15 #include <linux/wwan.h> 16 17 #define WWAN_MAX_MINORS 256 /* 256 minors allowed with register_chrdev() */ 18 19 static DEFINE_MUTEX(wwan_register_lock); /* WWAN device create|remove lock */ 20 static DEFINE_IDA(minors); /* minors for WWAN port chardevs */ 21 static DEFINE_IDA(wwan_dev_ids); /* for unique WWAN device IDs */ 22 static struct class *wwan_class; 23 static int wwan_major; 24 25 #define to_wwan_dev(d) container_of(d, struct wwan_device, dev) 26 #define to_wwan_port(d) container_of(d, struct wwan_port, dev) 27 28 /* WWAN port flags */ 29 #define WWAN_PORT_TX_OFF 0 30 31 /** 32 * struct wwan_device - The structure that defines a WWAN device 33 * 34 * @id: WWAN device unique ID. 35 * @dev: Underlying device. 36 * @port_id: Current available port ID to pick. 37 */ 38 struct wwan_device { 39 unsigned int id; 40 struct device dev; 41 atomic_t port_id; 42 }; 43 44 /** 45 * struct wwan_port - The structure that defines a WWAN port 46 * @type: Port type 47 * @start_count: Port start counter 48 * @flags: Store port state and capabilities 49 * @ops: Pointer to WWAN port operations 50 * @ops_lock: Protect port ops 51 * @dev: Underlying device 52 * @rxq: Buffer inbound queue 53 * @waitqueue: The waitqueue for port fops (read/write/poll) 54 */ 55 struct wwan_port { 56 enum wwan_port_type type; 57 unsigned int start_count; 58 unsigned long flags; 59 const struct wwan_port_ops *ops; 60 struct mutex ops_lock; /* Serialize ops + protect against removal */ 61 struct device dev; 62 struct sk_buff_head rxq; 63 wait_queue_head_t waitqueue; 64 }; 65 66 static ssize_t index_show(struct device *dev, struct device_attribute *attr, char *buf) 67 { 68 struct wwan_device *wwan = to_wwan_dev(dev); 69 70 return sprintf(buf, "%d\n", wwan->id); 71 } 72 static DEVICE_ATTR_RO(index); 73 74 static struct attribute *wwan_dev_attrs[] = { 75 &dev_attr_index.attr, 76 NULL, 77 }; 78 ATTRIBUTE_GROUPS(wwan_dev); 79 80 static void wwan_dev_destroy(struct device *dev) 81 { 82 struct wwan_device *wwandev = to_wwan_dev(dev); 83 84 ida_free(&wwan_dev_ids, wwandev->id); 85 kfree(wwandev); 86 } 87 88 static const struct device_type wwan_dev_type = { 89 .name = "wwan_dev", 90 .release = wwan_dev_destroy, 91 .groups = wwan_dev_groups, 92 }; 93 94 static int wwan_dev_parent_match(struct device *dev, const void *parent) 95 { 96 return (dev->type == &wwan_dev_type && dev->parent == parent); 97 } 98 99 static struct wwan_device *wwan_dev_get_by_parent(struct device *parent) 100 { 101 struct device *dev; 102 103 dev = class_find_device(wwan_class, NULL, parent, wwan_dev_parent_match); 104 if (!dev) 105 return ERR_PTR(-ENODEV); 106 107 return to_wwan_dev(dev); 108 } 109 110 /* This function allocates and registers a new WWAN device OR if a WWAN device 111 * already exist for the given parent, it gets a reference and return it. 112 * This function is not exported (for now), it is called indirectly via 113 * wwan_create_port(). 114 */ 115 static struct wwan_device *wwan_create_dev(struct device *parent) 116 { 117 struct wwan_device *wwandev; 118 int err, id; 119 120 /* The 'find-alloc-register' operation must be protected against 121 * concurrent execution, a WWAN device is possibly shared between 122 * multiple callers or concurrently unregistered from wwan_remove_dev(). 123 */ 124 mutex_lock(&wwan_register_lock); 125 126 /* If wwandev already exists, return it */ 127 wwandev = wwan_dev_get_by_parent(parent); 128 if (!IS_ERR(wwandev)) 129 goto done_unlock; 130 131 id = ida_alloc(&wwan_dev_ids, GFP_KERNEL); 132 if (id < 0) 133 goto done_unlock; 134 135 wwandev = kzalloc(sizeof(*wwandev), GFP_KERNEL); 136 if (!wwandev) { 137 ida_free(&wwan_dev_ids, id); 138 goto done_unlock; 139 } 140 141 wwandev->dev.parent = parent; 142 wwandev->dev.class = wwan_class; 143 wwandev->dev.type = &wwan_dev_type; 144 wwandev->id = id; 145 dev_set_name(&wwandev->dev, "wwan%d", wwandev->id); 146 147 err = device_register(&wwandev->dev); 148 if (err) { 149 put_device(&wwandev->dev); 150 wwandev = NULL; 151 } 152 153 done_unlock: 154 mutex_unlock(&wwan_register_lock); 155 156 return wwandev; 157 } 158 159 static int is_wwan_child(struct device *dev, void *data) 160 { 161 return dev->class == wwan_class; 162 } 163 164 static void wwan_remove_dev(struct wwan_device *wwandev) 165 { 166 int ret; 167 168 /* Prevent concurrent picking from wwan_create_dev */ 169 mutex_lock(&wwan_register_lock); 170 171 /* WWAN device is created and registered (get+add) along with its first 172 * child port, and subsequent port registrations only grab a reference 173 * (get). The WWAN device must then be unregistered (del+put) along with 174 * its latest port, and reference simply dropped (put) otherwise. 175 */ 176 ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child); 177 if (!ret) 178 device_unregister(&wwandev->dev); 179 else 180 put_device(&wwandev->dev); 181 182 mutex_unlock(&wwan_register_lock); 183 } 184 185 /* ------- WWAN port management ------- */ 186 187 /* Keep aligned with wwan_port_type enum */ 188 static const char * const wwan_port_type_str[] = { 189 "AT", 190 "MBIM", 191 "QMI", 192 "QCDM", 193 "FIREHOSE" 194 }; 195 196 static ssize_t type_show(struct device *dev, struct device_attribute *attr, 197 char *buf) 198 { 199 struct wwan_port *port = to_wwan_port(dev); 200 201 return sprintf(buf, "%s\n", wwan_port_type_str[port->type]); 202 } 203 static DEVICE_ATTR_RO(type); 204 205 static struct attribute *wwan_port_attrs[] = { 206 &dev_attr_type.attr, 207 NULL, 208 }; 209 ATTRIBUTE_GROUPS(wwan_port); 210 211 static void wwan_port_destroy(struct device *dev) 212 { 213 struct wwan_port *port = to_wwan_port(dev); 214 215 ida_free(&minors, MINOR(port->dev.devt)); 216 skb_queue_purge(&port->rxq); 217 mutex_destroy(&port->ops_lock); 218 kfree(port); 219 } 220 221 static const struct device_type wwan_port_dev_type = { 222 .name = "wwan_port", 223 .release = wwan_port_destroy, 224 .groups = wwan_port_groups, 225 }; 226 227 static int wwan_port_minor_match(struct device *dev, const void *minor) 228 { 229 return (dev->type == &wwan_port_dev_type && 230 MINOR(dev->devt) == *(unsigned int *)minor); 231 } 232 233 static struct wwan_port *wwan_port_get_by_minor(unsigned int minor) 234 { 235 struct device *dev; 236 237 dev = class_find_device(wwan_class, NULL, &minor, wwan_port_minor_match); 238 if (!dev) 239 return ERR_PTR(-ENODEV); 240 241 return to_wwan_port(dev); 242 } 243 244 struct wwan_port *wwan_create_port(struct device *parent, 245 enum wwan_port_type type, 246 const struct wwan_port_ops *ops, 247 void *drvdata) 248 { 249 struct wwan_device *wwandev; 250 struct wwan_port *port; 251 int minor, err = -ENOMEM; 252 253 if (type >= WWAN_PORT_MAX || !ops) 254 return ERR_PTR(-EINVAL); 255 256 /* A port is always a child of a WWAN device, retrieve (allocate or 257 * pick) the WWAN device based on the provided parent device. 258 */ 259 wwandev = wwan_create_dev(parent); 260 if (IS_ERR(wwandev)) 261 return ERR_CAST(wwandev); 262 263 /* A port is exposed as character device, get a minor */ 264 minor = ida_alloc_range(&minors, 0, WWAN_MAX_MINORS - 1, GFP_KERNEL); 265 if (minor < 0) 266 goto error_wwandev_remove; 267 268 port = kzalloc(sizeof(*port), GFP_KERNEL); 269 if (!port) { 270 ida_free(&minors, minor); 271 goto error_wwandev_remove; 272 } 273 274 port->type = type; 275 port->ops = ops; 276 mutex_init(&port->ops_lock); 277 skb_queue_head_init(&port->rxq); 278 init_waitqueue_head(&port->waitqueue); 279 280 port->dev.parent = &wwandev->dev; 281 port->dev.class = wwan_class; 282 port->dev.type = &wwan_port_dev_type; 283 port->dev.devt = MKDEV(wwan_major, minor); 284 dev_set_drvdata(&port->dev, drvdata); 285 286 /* create unique name based on wwan device id, port index and type */ 287 dev_set_name(&port->dev, "wwan%up%u%s", wwandev->id, 288 atomic_inc_return(&wwandev->port_id), 289 wwan_port_type_str[port->type]); 290 291 err = device_register(&port->dev); 292 if (err) 293 goto error_put_device; 294 295 return port; 296 297 error_put_device: 298 put_device(&port->dev); 299 error_wwandev_remove: 300 wwan_remove_dev(wwandev); 301 302 return ERR_PTR(err); 303 } 304 EXPORT_SYMBOL_GPL(wwan_create_port); 305 306 void wwan_remove_port(struct wwan_port *port) 307 { 308 struct wwan_device *wwandev = to_wwan_dev(port->dev.parent); 309 310 mutex_lock(&port->ops_lock); 311 if (port->start_count) 312 port->ops->stop(port); 313 port->ops = NULL; /* Prevent any new port operations (e.g. from fops) */ 314 mutex_unlock(&port->ops_lock); 315 316 wake_up_interruptible(&port->waitqueue); 317 318 skb_queue_purge(&port->rxq); 319 dev_set_drvdata(&port->dev, NULL); 320 device_unregister(&port->dev); 321 322 /* Release related wwan device */ 323 wwan_remove_dev(wwandev); 324 } 325 EXPORT_SYMBOL_GPL(wwan_remove_port); 326 327 void wwan_port_rx(struct wwan_port *port, struct sk_buff *skb) 328 { 329 skb_queue_tail(&port->rxq, skb); 330 wake_up_interruptible(&port->waitqueue); 331 } 332 EXPORT_SYMBOL_GPL(wwan_port_rx); 333 334 void wwan_port_txon(struct wwan_port *port) 335 { 336 clear_bit(WWAN_PORT_TX_OFF, &port->flags); 337 wake_up_interruptible(&port->waitqueue); 338 } 339 EXPORT_SYMBOL_GPL(wwan_port_txon); 340 341 void wwan_port_txoff(struct wwan_port *port) 342 { 343 set_bit(WWAN_PORT_TX_OFF, &port->flags); 344 } 345 EXPORT_SYMBOL_GPL(wwan_port_txoff); 346 347 void *wwan_port_get_drvdata(struct wwan_port *port) 348 { 349 return dev_get_drvdata(&port->dev); 350 } 351 EXPORT_SYMBOL_GPL(wwan_port_get_drvdata); 352 353 static int wwan_port_op_start(struct wwan_port *port) 354 { 355 int ret = 0; 356 357 mutex_lock(&port->ops_lock); 358 if (!port->ops) { /* Port got unplugged */ 359 ret = -ENODEV; 360 goto out_unlock; 361 } 362 363 /* If port is already started, don't start again */ 364 if (!port->start_count) 365 ret = port->ops->start(port); 366 367 if (!ret) 368 port->start_count++; 369 370 out_unlock: 371 mutex_unlock(&port->ops_lock); 372 373 return ret; 374 } 375 376 static void wwan_port_op_stop(struct wwan_port *port) 377 { 378 mutex_lock(&port->ops_lock); 379 port->start_count--; 380 if (port->ops && !port->start_count) 381 port->ops->stop(port); 382 mutex_unlock(&port->ops_lock); 383 } 384 385 static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb) 386 { 387 int ret; 388 389 mutex_lock(&port->ops_lock); 390 if (!port->ops) { /* Port got unplugged */ 391 ret = -ENODEV; 392 goto out_unlock; 393 } 394 395 ret = port->ops->tx(port, skb); 396 397 out_unlock: 398 mutex_unlock(&port->ops_lock); 399 400 return ret; 401 } 402 403 static bool is_read_blocked(struct wwan_port *port) 404 { 405 return skb_queue_empty(&port->rxq) && port->ops; 406 } 407 408 static bool is_write_blocked(struct wwan_port *port) 409 { 410 return test_bit(WWAN_PORT_TX_OFF, &port->flags) && port->ops; 411 } 412 413 static int wwan_wait_rx(struct wwan_port *port, bool nonblock) 414 { 415 if (!is_read_blocked(port)) 416 return 0; 417 418 if (nonblock) 419 return -EAGAIN; 420 421 if (wait_event_interruptible(port->waitqueue, !is_read_blocked(port))) 422 return -ERESTARTSYS; 423 424 return 0; 425 } 426 427 static int wwan_wait_tx(struct wwan_port *port, bool nonblock) 428 { 429 if (!is_write_blocked(port)) 430 return 0; 431 432 if (nonblock) 433 return -EAGAIN; 434 435 if (wait_event_interruptible(port->waitqueue, !is_write_blocked(port))) 436 return -ERESTARTSYS; 437 438 return 0; 439 } 440 441 static int wwan_port_fops_open(struct inode *inode, struct file *file) 442 { 443 struct wwan_port *port; 444 int err = 0; 445 446 port = wwan_port_get_by_minor(iminor(inode)); 447 if (IS_ERR(port)) 448 return PTR_ERR(port); 449 450 file->private_data = port; 451 stream_open(inode, file); 452 453 err = wwan_port_op_start(port); 454 if (err) 455 put_device(&port->dev); 456 457 return err; 458 } 459 460 static int wwan_port_fops_release(struct inode *inode, struct file *filp) 461 { 462 struct wwan_port *port = filp->private_data; 463 464 wwan_port_op_stop(port); 465 put_device(&port->dev); 466 467 return 0; 468 } 469 470 static ssize_t wwan_port_fops_read(struct file *filp, char __user *buf, 471 size_t count, loff_t *ppos) 472 { 473 struct wwan_port *port = filp->private_data; 474 struct sk_buff *skb; 475 size_t copied; 476 int ret; 477 478 ret = wwan_wait_rx(port, !!(filp->f_flags & O_NONBLOCK)); 479 if (ret) 480 return ret; 481 482 skb = skb_dequeue(&port->rxq); 483 if (!skb) 484 return -EIO; 485 486 copied = min_t(size_t, count, skb->len); 487 if (copy_to_user(buf, skb->data, copied)) { 488 kfree_skb(skb); 489 return -EFAULT; 490 } 491 skb_pull(skb, copied); 492 493 /* skb is not fully consumed, keep it in the queue */ 494 if (skb->len) 495 skb_queue_head(&port->rxq, skb); 496 else 497 consume_skb(skb); 498 499 return copied; 500 } 501 502 static ssize_t wwan_port_fops_write(struct file *filp, const char __user *buf, 503 size_t count, loff_t *offp) 504 { 505 struct wwan_port *port = filp->private_data; 506 struct sk_buff *skb; 507 int ret; 508 509 ret = wwan_wait_tx(port, !!(filp->f_flags & O_NONBLOCK)); 510 if (ret) 511 return ret; 512 513 skb = alloc_skb(count, GFP_KERNEL); 514 if (!skb) 515 return -ENOMEM; 516 517 if (copy_from_user(skb_put(skb, count), buf, count)) { 518 kfree_skb(skb); 519 return -EFAULT; 520 } 521 522 ret = wwan_port_op_tx(port, skb); 523 if (ret) { 524 kfree_skb(skb); 525 return ret; 526 } 527 528 return count; 529 } 530 531 static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait) 532 { 533 struct wwan_port *port = filp->private_data; 534 __poll_t mask = 0; 535 536 poll_wait(filp, &port->waitqueue, wait); 537 538 if (!is_write_blocked(port)) 539 mask |= EPOLLOUT | EPOLLWRNORM; 540 if (!is_read_blocked(port)) 541 mask |= EPOLLIN | EPOLLRDNORM; 542 if (!port->ops) 543 mask |= EPOLLHUP | EPOLLERR; 544 545 return mask; 546 } 547 548 static const struct file_operations wwan_port_fops = { 549 .owner = THIS_MODULE, 550 .open = wwan_port_fops_open, 551 .release = wwan_port_fops_release, 552 .read = wwan_port_fops_read, 553 .write = wwan_port_fops_write, 554 .poll = wwan_port_fops_poll, 555 .llseek = noop_llseek, 556 }; 557 558 static int __init wwan_init(void) 559 { 560 wwan_class = class_create(THIS_MODULE, "wwan"); 561 if (IS_ERR(wwan_class)) 562 return PTR_ERR(wwan_class); 563 564 /* chrdev used for wwan ports */ 565 wwan_major = register_chrdev(0, "wwan_port", &wwan_port_fops); 566 if (wwan_major < 0) { 567 class_destroy(wwan_class); 568 return wwan_major; 569 } 570 571 return 0; 572 } 573 574 static void __exit wwan_exit(void) 575 { 576 unregister_chrdev(wwan_major, "wwan_port"); 577 class_destroy(wwan_class); 578 } 579 580 module_init(wwan_init); 581 module_exit(wwan_exit); 582 583 MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>"); 584 MODULE_DESCRIPTION("WWAN core"); 585 MODULE_LICENSE("GPL v2"); 586