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