xref: /f-stack/dpdk/kernel/linux/kni/kni_misc.c (revision fa64a7ff)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright(c) 2010-2014 Intel Corporation.
4  */
5 
6 #include <linux/version.h>
7 #include <linux/module.h>
8 #include <linux/miscdevice.h>
9 #include <linux/netdevice.h>
10 #include <linux/etherdevice.h>
11 #include <linux/pci.h>
12 #include <linux/kthread.h>
13 #include <linux/rwsem.h>
14 #include <linux/mutex.h>
15 #include <linux/nsproxy.h>
16 #include <net/net_namespace.h>
17 #include <net/netns/generic.h>
18 
19 #include <exec-env/rte_kni_common.h>
20 
21 #include "compat.h"
22 #include "kni_dev.h"
23 
24 MODULE_LICENSE("Dual BSD/GPL");
25 MODULE_AUTHOR("Intel Corporation");
26 MODULE_DESCRIPTION("Kernel Module for managing kni devices");
27 
28 #define KNI_RX_LOOP_NUM 1000
29 
30 #define KNI_MAX_DEVICES 32
31 
32 extern const struct pci_device_id ixgbe_pci_tbl[];
33 extern const struct pci_device_id igb_pci_tbl[];
34 
35 /* loopback mode */
36 static char *lo_mode;
37 
38 /* Kernel thread mode */
39 static char *kthread_mode;
40 static uint32_t multiple_kthread_on;
41 
42 /* Default carrier state for created KNI network interfaces */
43 static char *carrier;
44 uint32_t dflt_carrier;
45 
46 #define KNI_DEV_IN_USE_BIT_NUM 0 /* Bit number for device in use */
47 
48 static int kni_net_id;
49 
50 struct kni_net {
51 	unsigned long device_in_use; /* device in use flag */
52 	struct mutex kni_kthread_lock;
53 	struct task_struct *kni_kthread;
54 	struct rw_semaphore kni_list_lock;
55 	struct list_head kni_list_head;
56 };
57 
58 static int __net_init
59 kni_init_net(struct net *net)
60 {
61 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
62 	struct kni_net *knet = net_generic(net, kni_net_id);
63 
64 	memset(knet, 0, sizeof(*knet));
65 #else
66 	struct kni_net *knet;
67 	int ret;
68 
69 	knet = kzalloc(sizeof(struct kni_net), GFP_KERNEL);
70 	if (!knet) {
71 		ret = -ENOMEM;
72 		return ret;
73 	}
74 #endif
75 
76 	/* Clear the bit of device in use */
77 	clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
78 
79 	mutex_init(&knet->kni_kthread_lock);
80 
81 	init_rwsem(&knet->kni_list_lock);
82 	INIT_LIST_HEAD(&knet->kni_list_head);
83 
84 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
85 	return 0;
86 #else
87 	ret = net_assign_generic(net, kni_net_id, knet);
88 	if (ret < 0)
89 		kfree(knet);
90 
91 	return ret;
92 #endif
93 }
94 
95 static void __net_exit
96 kni_exit_net(struct net *net)
97 {
98 	struct kni_net *knet __maybe_unused;
99 
100 	knet = net_generic(net, kni_net_id);
101 	mutex_destroy(&knet->kni_kthread_lock);
102 
103 #ifndef HAVE_SIMPLIFIED_PERNET_OPERATIONS
104 	kfree(knet);
105 #endif
106 }
107 
108 static struct pernet_operations kni_net_ops = {
109 	.init = kni_init_net,
110 	.exit = kni_exit_net,
111 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
112 	.id   = &kni_net_id,
113 	.size = sizeof(struct kni_net),
114 #endif
115 };
116 
117 static int
118 kni_thread_single(void *data)
119 {
120 	struct kni_net *knet = data;
121 	int j;
122 	struct kni_dev *dev;
123 
124 	while (!kthread_should_stop()) {
125 		down_read(&knet->kni_list_lock);
126 		for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
127 			list_for_each_entry(dev, &knet->kni_list_head, list) {
128 				kni_net_rx(dev);
129 				kni_net_poll_resp(dev);
130 			}
131 		}
132 		up_read(&knet->kni_list_lock);
133 #ifdef RTE_KNI_PREEMPT_DEFAULT
134 		/* reschedule out for a while */
135 		schedule_timeout_interruptible(
136 			usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL));
137 #endif
138 	}
139 
140 	return 0;
141 }
142 
143 static int
144 kni_thread_multiple(void *param)
145 {
146 	int j;
147 	struct kni_dev *dev = param;
148 
149 	while (!kthread_should_stop()) {
150 		for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
151 			kni_net_rx(dev);
152 			kni_net_poll_resp(dev);
153 		}
154 #ifdef RTE_KNI_PREEMPT_DEFAULT
155 		schedule_timeout_interruptible(
156 			usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL));
157 #endif
158 	}
159 
160 	return 0;
161 }
162 
163 static int
164 kni_open(struct inode *inode, struct file *file)
165 {
166 	struct net *net = current->nsproxy->net_ns;
167 	struct kni_net *knet = net_generic(net, kni_net_id);
168 
169 	/* kni device can be opened by one user only per netns */
170 	if (test_and_set_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use))
171 		return -EBUSY;
172 
173 	file->private_data = get_net(net);
174 	pr_debug("/dev/kni opened\n");
175 
176 	return 0;
177 }
178 
179 static int
180 kni_dev_remove(struct kni_dev *dev)
181 {
182 	if (!dev)
183 		return -ENODEV;
184 
185 #ifdef RTE_KNI_KMOD_ETHTOOL
186 	if (dev->pci_dev) {
187 		if (pci_match_id(ixgbe_pci_tbl, dev->pci_dev))
188 			ixgbe_kni_remove(dev->pci_dev);
189 		else if (pci_match_id(igb_pci_tbl, dev->pci_dev))
190 			igb_kni_remove(dev->pci_dev);
191 	}
192 #endif
193 
194 	if (dev->net_dev) {
195 		unregister_netdev(dev->net_dev);
196 		free_netdev(dev->net_dev);
197 	}
198 
199 	kni_net_release_fifo_phy(dev);
200 
201 	return 0;
202 }
203 
204 static int
205 kni_release(struct inode *inode, struct file *file)
206 {
207 	struct net *net = file->private_data;
208 	struct kni_net *knet = net_generic(net, kni_net_id);
209 	struct kni_dev *dev, *n;
210 
211 	/* Stop kernel thread for single mode */
212 	if (multiple_kthread_on == 0) {
213 		mutex_lock(&knet->kni_kthread_lock);
214 		/* Stop kernel thread */
215 		if (knet->kni_kthread != NULL) {
216 			kthread_stop(knet->kni_kthread);
217 			knet->kni_kthread = NULL;
218 		}
219 		mutex_unlock(&knet->kni_kthread_lock);
220 	}
221 
222 	down_write(&knet->kni_list_lock);
223 	list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
224 		/* Stop kernel thread for multiple mode */
225 		if (multiple_kthread_on && dev->pthread != NULL) {
226 			kthread_stop(dev->pthread);
227 			dev->pthread = NULL;
228 		}
229 
230 		kni_dev_remove(dev);
231 		list_del(&dev->list);
232 	}
233 	up_write(&knet->kni_list_lock);
234 
235 	/* Clear the bit of device in use */
236 	clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
237 
238 	put_net(net);
239 	pr_debug("/dev/kni closed\n");
240 
241 	return 0;
242 }
243 
244 static int
245 kni_check_param(struct kni_dev *kni, struct rte_kni_device_info *dev)
246 {
247 	if (!kni || !dev)
248 		return -1;
249 
250 	/* Check if network name has been used */
251 	if (!strncmp(kni->name, dev->name, RTE_KNI_NAMESIZE)) {
252 		pr_err("KNI name %s duplicated\n", dev->name);
253 		return -1;
254 	}
255 
256 	return 0;
257 }
258 
259 static int
260 kni_run_thread(struct kni_net *knet, struct kni_dev *kni, uint8_t force_bind)
261 {
262 	/**
263 	 * Create a new kernel thread for multiple mode, set its core affinity,
264 	 * and finally wake it up.
265 	 */
266 	if (multiple_kthread_on) {
267 		kni->pthread = kthread_create(kni_thread_multiple,
268 			(void *)kni, "kni_%s", kni->name);
269 		if (IS_ERR(kni->pthread)) {
270 			kni_dev_remove(kni);
271 			return -ECANCELED;
272 		}
273 
274 		if (force_bind)
275 			kthread_bind(kni->pthread, kni->core_id);
276 		wake_up_process(kni->pthread);
277 	} else {
278 		mutex_lock(&knet->kni_kthread_lock);
279 
280 		if (knet->kni_kthread == NULL) {
281 			knet->kni_kthread = kthread_create(kni_thread_single,
282 				(void *)knet, "kni_single");
283 			if (IS_ERR(knet->kni_kthread)) {
284 				mutex_unlock(&knet->kni_kthread_lock);
285 				kni_dev_remove(kni);
286 				return -ECANCELED;
287 			}
288 
289 			if (force_bind)
290 				kthread_bind(knet->kni_kthread, kni->core_id);
291 			wake_up_process(knet->kni_kthread);
292 		}
293 
294 		mutex_unlock(&knet->kni_kthread_lock);
295 	}
296 
297 	return 0;
298 }
299 
300 static int
301 kni_ioctl_create(struct net *net, uint32_t ioctl_num,
302 		unsigned long ioctl_param)
303 {
304 	struct kni_net *knet = net_generic(net, kni_net_id);
305 	int ret;
306 	struct rte_kni_device_info dev_info;
307 	struct net_device *net_dev = NULL;
308 	struct kni_dev *kni, *dev, *n;
309 #ifdef RTE_KNI_KMOD_ETHTOOL
310 	struct pci_dev *found_pci = NULL;
311 	struct net_device *lad_dev = NULL;
312 	struct pci_dev *pci = NULL;
313 #endif
314 
315 	pr_info("Creating kni...\n");
316 	/* Check the buffer size, to avoid warning */
317 	if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
318 		return -EINVAL;
319 
320 	/* Copy kni info from user space */
321 	if (copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info)))
322 		return -EFAULT;
323 
324 	/* Check if name is zero-ended */
325 	if (strnlen(dev_info.name, sizeof(dev_info.name)) == sizeof(dev_info.name)) {
326 		pr_err("kni.name not zero-terminated");
327 		return -EINVAL;
328 	}
329 
330 	/**
331 	 * Check if the cpu core id is valid for binding.
332 	 */
333 	if (dev_info.force_bind && !cpu_online(dev_info.core_id)) {
334 		pr_err("cpu %u is not online\n", dev_info.core_id);
335 		return -EINVAL;
336 	}
337 
338 	/* Check if it has been created */
339 	down_read(&knet->kni_list_lock);
340 	list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
341 		if (kni_check_param(dev, &dev_info) < 0) {
342 			up_read(&knet->kni_list_lock);
343 			return -EINVAL;
344 		}
345 	}
346 	up_read(&knet->kni_list_lock);
347 
348 	net_dev = alloc_netdev(sizeof(struct kni_dev), dev_info.name,
349 #ifdef NET_NAME_USER
350 							NET_NAME_USER,
351 #endif
352 							kni_net_init);
353 	if (net_dev == NULL) {
354 		pr_err("error allocating device \"%s\"\n", dev_info.name);
355 		return -EBUSY;
356 	}
357 
358 	dev_net_set(net_dev, net);
359 
360 	kni = netdev_priv(net_dev);
361 
362 	kni->net_dev = net_dev;
363 	kni->group_id = dev_info.group_id;
364 	kni->core_id = dev_info.core_id;
365 	strncpy(kni->name, dev_info.name, RTE_KNI_NAMESIZE);
366 
367 	/* Translate user space info into kernel space info */
368 	kni->tx_q = phys_to_virt(dev_info.tx_phys);
369 	kni->rx_q = phys_to_virt(dev_info.rx_phys);
370 	kni->alloc_q = phys_to_virt(dev_info.alloc_phys);
371 	kni->free_q = phys_to_virt(dev_info.free_phys);
372 
373 	kni->req_q = phys_to_virt(dev_info.req_phys);
374 	kni->resp_q = phys_to_virt(dev_info.resp_phys);
375 	kni->sync_va = dev_info.sync_va;
376 	kni->sync_kva = phys_to_virt(dev_info.sync_phys);
377 
378 	kni->mbuf_size = dev_info.mbuf_size;
379 
380 	pr_debug("tx_phys:      0x%016llx, tx_q addr:      0x%p\n",
381 		(unsigned long long) dev_info.tx_phys, kni->tx_q);
382 	pr_debug("rx_phys:      0x%016llx, rx_q addr:      0x%p\n",
383 		(unsigned long long) dev_info.rx_phys, kni->rx_q);
384 	pr_debug("alloc_phys:   0x%016llx, alloc_q addr:   0x%p\n",
385 		(unsigned long long) dev_info.alloc_phys, kni->alloc_q);
386 	pr_debug("free_phys:    0x%016llx, free_q addr:    0x%p\n",
387 		(unsigned long long) dev_info.free_phys, kni->free_q);
388 	pr_debug("req_phys:     0x%016llx, req_q addr:     0x%p\n",
389 		(unsigned long long) dev_info.req_phys, kni->req_q);
390 	pr_debug("resp_phys:    0x%016llx, resp_q addr:    0x%p\n",
391 		(unsigned long long) dev_info.resp_phys, kni->resp_q);
392 	pr_debug("mbuf_size:    %u\n", kni->mbuf_size);
393 
394 	pr_debug("PCI: %02x:%02x.%02x %04x:%04x\n",
395 					dev_info.bus,
396 					dev_info.devid,
397 					dev_info.function,
398 					dev_info.vendor_id,
399 					dev_info.device_id);
400 #ifdef RTE_KNI_KMOD_ETHTOOL
401 	pci = pci_get_device(dev_info.vendor_id, dev_info.device_id, NULL);
402 
403 	/* Support Ethtool */
404 	while (pci) {
405 		pr_debug("pci_bus: %02x:%02x:%02x\n",
406 					pci->bus->number,
407 					PCI_SLOT(pci->devfn),
408 					PCI_FUNC(pci->devfn));
409 
410 		if ((pci->bus->number == dev_info.bus) &&
411 			(PCI_SLOT(pci->devfn) == dev_info.devid) &&
412 			(PCI_FUNC(pci->devfn) == dev_info.function)) {
413 			found_pci = pci;
414 
415 			if (pci_match_id(ixgbe_pci_tbl, found_pci))
416 				ret = ixgbe_kni_probe(found_pci, &lad_dev);
417 			else if (pci_match_id(igb_pci_tbl, found_pci))
418 				ret = igb_kni_probe(found_pci, &lad_dev);
419 			else
420 				ret = -1;
421 
422 			pr_debug("PCI found: pci=0x%p, lad_dev=0x%p\n",
423 							pci, lad_dev);
424 			if (ret == 0) {
425 				kni->lad_dev = lad_dev;
426 				kni_set_ethtool_ops(kni->net_dev);
427 			} else {
428 				pr_err("Device not supported by ethtool");
429 				kni->lad_dev = NULL;
430 			}
431 
432 			kni->pci_dev = found_pci;
433 			kni->device_id = dev_info.device_id;
434 			break;
435 		}
436 		pci = pci_get_device(dev_info.vendor_id,
437 				dev_info.device_id, pci);
438 	}
439 	if (pci)
440 		pci_dev_put(pci);
441 #endif
442 
443 	if (kni->lad_dev)
444 		ether_addr_copy(net_dev->dev_addr, kni->lad_dev->dev_addr);
445 	else {
446 		/* if user has provided a valid mac address */
447 		if (is_valid_ether_addr(dev_info.mac_addr))
448 			memcpy(net_dev->dev_addr, dev_info.mac_addr, ETH_ALEN);
449 		else
450 			/*
451 			 * Generate random mac address. eth_random_addr() is the
452 			 * newer version of generating mac address in kernel.
453 			 */
454 			random_ether_addr(net_dev->dev_addr);
455 	}
456 
457 	if (dev_info.mtu)
458 		net_dev->mtu = dev_info.mtu;
459 
460 	ret = register_netdev(net_dev);
461 	if (ret) {
462 		pr_err("error %i registering device \"%s\"\n",
463 					ret, dev_info.name);
464 		kni->net_dev = NULL;
465 		kni_dev_remove(kni);
466 		free_netdev(net_dev);
467 		return -ENODEV;
468 	}
469 
470 	netif_carrier_off(net_dev);
471 
472 	ret = kni_run_thread(knet, kni, dev_info.force_bind);
473 	if (ret != 0)
474 		return ret;
475 
476 	down_write(&knet->kni_list_lock);
477 	list_add(&kni->list, &knet->kni_list_head);
478 	up_write(&knet->kni_list_lock);
479 
480 	return 0;
481 }
482 
483 static int
484 kni_ioctl_release(struct net *net, uint32_t ioctl_num,
485 		unsigned long ioctl_param)
486 {
487 	struct kni_net *knet = net_generic(net, kni_net_id);
488 	int ret = -EINVAL;
489 	struct kni_dev *dev, *n;
490 	struct rte_kni_device_info dev_info;
491 
492 	if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
493 		return -EINVAL;
494 
495 	if (copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info)))
496 		return -EFAULT;
497 
498 	/* Release the network device according to its name */
499 	if (strlen(dev_info.name) == 0)
500 		return -EINVAL;
501 
502 	down_write(&knet->kni_list_lock);
503 	list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
504 		if (strncmp(dev->name, dev_info.name, RTE_KNI_NAMESIZE) != 0)
505 			continue;
506 
507 		if (multiple_kthread_on && dev->pthread != NULL) {
508 			kthread_stop(dev->pthread);
509 			dev->pthread = NULL;
510 		}
511 
512 		kni_dev_remove(dev);
513 		list_del(&dev->list);
514 		ret = 0;
515 		break;
516 	}
517 	up_write(&knet->kni_list_lock);
518 	pr_info("%s release kni named %s\n",
519 		(ret == 0 ? "Successfully" : "Unsuccessfully"), dev_info.name);
520 
521 	return ret;
522 }
523 
524 static int
525 kni_ioctl(struct inode *inode, uint32_t ioctl_num, unsigned long ioctl_param)
526 {
527 	int ret = -EINVAL;
528 	struct net *net = current->nsproxy->net_ns;
529 
530 	pr_debug("IOCTL num=0x%0x param=0x%0lx\n", ioctl_num, ioctl_param);
531 
532 	/*
533 	 * Switch according to the ioctl called
534 	 */
535 	switch (_IOC_NR(ioctl_num)) {
536 	case _IOC_NR(RTE_KNI_IOCTL_TEST):
537 		/* For test only, not used */
538 		break;
539 	case _IOC_NR(RTE_KNI_IOCTL_CREATE):
540 		ret = kni_ioctl_create(net, ioctl_num, ioctl_param);
541 		break;
542 	case _IOC_NR(RTE_KNI_IOCTL_RELEASE):
543 		ret = kni_ioctl_release(net, ioctl_num, ioctl_param);
544 		break;
545 	default:
546 		pr_debug("IOCTL default\n");
547 		break;
548 	}
549 
550 	return ret;
551 }
552 
553 static int
554 kni_compat_ioctl(struct inode *inode, uint32_t ioctl_num,
555 		unsigned long ioctl_param)
556 {
557 	/* 32 bits app on 64 bits OS to be supported later */
558 	pr_debug("Not implemented.\n");
559 
560 	return -EINVAL;
561 }
562 
563 static const struct file_operations kni_fops = {
564 	.owner = THIS_MODULE,
565 	.open = kni_open,
566 	.release = kni_release,
567 	.unlocked_ioctl = (void *)kni_ioctl,
568 	.compat_ioctl = (void *)kni_compat_ioctl,
569 };
570 
571 static struct miscdevice kni_misc = {
572 	.minor = MISC_DYNAMIC_MINOR,
573 	.name = KNI_DEVICE,
574 	.fops = &kni_fops,
575 };
576 
577 static int __init
578 kni_parse_kthread_mode(void)
579 {
580 	if (!kthread_mode)
581 		return 0;
582 
583 	if (strcmp(kthread_mode, "single") == 0)
584 		return 0;
585 	else if (strcmp(kthread_mode, "multiple") == 0)
586 		multiple_kthread_on = 1;
587 	else
588 		return -1;
589 
590 	return 0;
591 }
592 
593 static int __init
594 kni_parse_carrier_state(void)
595 {
596 	if (!carrier) {
597 		dflt_carrier = 0;
598 		return 0;
599 	}
600 
601 	if (strcmp(carrier, "off") == 0)
602 		dflt_carrier = 0;
603 	else if (strcmp(carrier, "on") == 0)
604 		dflt_carrier = 1;
605 	else
606 		return -1;
607 
608 	return 0;
609 }
610 
611 static int __init
612 kni_init(void)
613 {
614 	int rc;
615 
616 	if (kni_parse_kthread_mode() < 0) {
617 		pr_err("Invalid parameter for kthread_mode\n");
618 		return -EINVAL;
619 	}
620 
621 	if (multiple_kthread_on == 0)
622 		pr_debug("Single kernel thread for all KNI devices\n");
623 	else
624 		pr_debug("Multiple kernel thread mode enabled\n");
625 
626 	if (kni_parse_carrier_state() < 0) {
627 		pr_err("Invalid parameter for carrier\n");
628 		return -EINVAL;
629 	}
630 
631 	if (dflt_carrier == 0)
632 		pr_debug("Default carrier state set to off.\n");
633 	else
634 		pr_debug("Default carrier state set to on.\n");
635 
636 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
637 	rc = register_pernet_subsys(&kni_net_ops);
638 #else
639 	rc = register_pernet_gen_subsys(&kni_net_id, &kni_net_ops);
640 #endif
641 	if (rc)
642 		return -EPERM;
643 
644 	rc = misc_register(&kni_misc);
645 	if (rc != 0) {
646 		pr_err("Misc registration failed\n");
647 		goto out;
648 	}
649 
650 	/* Configure the lo mode according to the input parameter */
651 	kni_net_config_lo_mode(lo_mode);
652 
653 	return 0;
654 
655 out:
656 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
657 	unregister_pernet_subsys(&kni_net_ops);
658 #else
659 	unregister_pernet_gen_subsys(kni_net_id, &kni_net_ops);
660 #endif
661 	return rc;
662 }
663 
664 static void __exit
665 kni_exit(void)
666 {
667 	misc_deregister(&kni_misc);
668 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
669 	unregister_pernet_subsys(&kni_net_ops);
670 #else
671 	unregister_pernet_gen_subsys(kni_net_id, &kni_net_ops);
672 #endif
673 }
674 
675 module_init(kni_init);
676 module_exit(kni_exit);
677 
678 module_param(lo_mode, charp, 0644);
679 MODULE_PARM_DESC(lo_mode,
680 "KNI loopback mode (default=lo_mode_none):\n"
681 "\t\tlo_mode_none        Kernel loopback disabled\n"
682 "\t\tlo_mode_fifo        Enable kernel loopback with fifo\n"
683 "\t\tlo_mode_fifo_skb    Enable kernel loopback with fifo and skb buffer\n"
684 "\t\t"
685 );
686 
687 module_param(kthread_mode, charp, 0644);
688 MODULE_PARM_DESC(kthread_mode,
689 "Kernel thread mode (default=single):\n"
690 "\t\tsingle    Single kernel thread mode enabled.\n"
691 "\t\tmultiple  Multiple kernel thread mode enabled.\n"
692 "\t\t"
693 );
694 
695 module_param(carrier, charp, 0644);
696 MODULE_PARM_DESC(carrier,
697 "Default carrier state for KNI interface (default=off):\n"
698 "\t\toff   Interfaces will be created with carrier state set to off.\n"
699 "\t\ton    Interfaces will be created with carrier state set to on.\n"
700 "\t\t"
701 );
702