1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) ST-Ericsson AB 2010
4 * Author:	Sjur Brendeland
5 */
6
7#include <linux/hardirq.h>
8#include <linux/init.h>
9#include <linux/module.h>
10#include <linux/device.h>
11#include <linux/types.h>
12#include <linux/skbuff.h>
13#include <linux/netdevice.h>
14#include <linux/rtnetlink.h>
15#include <linux/tty.h>
16#include <linux/file.h>
17#include <linux/if_arp.h>
18#include <net/caif/caif_device.h>
19#include <net/caif/cfcnfg.h>
20#include <linux/err.h>
21#include <linux/debugfs.h>
22
23MODULE_LICENSE("GPL");
24MODULE_AUTHOR("Sjur Brendeland");
25MODULE_DESCRIPTION("CAIF serial device TTY line discipline");
26MODULE_LICENSE("GPL");
27MODULE_ALIAS_LDISC(N_CAIF);
28
29#define SEND_QUEUE_LOW 10
30#define SEND_QUEUE_HIGH 100
31#define CAIF_SENDING	        1 /* Bit 1 = 0x02*/
32#define CAIF_FLOW_OFF_SENT	4 /* Bit 4 = 0x10 */
33#define MAX_WRITE_CHUNK	     4096
34#define ON 1
35#define OFF 0
36#define CAIF_MAX_MTU 4096
37
38static DEFINE_SPINLOCK(ser_lock);
39static LIST_HEAD(ser_list);
40static LIST_HEAD(ser_release_list);
41
42static bool ser_loop;
43module_param(ser_loop, bool, 0444);
44MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
45
46static bool ser_use_stx = true;
47module_param(ser_use_stx, bool, 0444);
48MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
49
50static bool ser_use_fcs = true;
51
52module_param(ser_use_fcs, bool, 0444);
53MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
54
55static int ser_write_chunk = MAX_WRITE_CHUNK;
56module_param(ser_write_chunk, int, 0444);
57
58MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
59
60static struct dentry *debugfsdir;
61
62static int caif_net_open(struct net_device *dev);
63static int caif_net_close(struct net_device *dev);
64
65struct ser_device {
66	struct caif_dev_common common;
67	struct list_head node;
68	struct net_device *dev;
69	struct sk_buff_head head;
70	struct tty_struct *tty;
71	bool tx_started;
72	unsigned long state;
73#ifdef CONFIG_DEBUG_FS
74	struct dentry *debugfs_tty_dir;
75	struct debugfs_blob_wrapper tx_blob;
76	struct debugfs_blob_wrapper rx_blob;
77	u8 rx_data[128];
78	u8 tx_data[128];
79	u8 tty_status;
80
81#endif
82};
83
84static void caifdev_setup(struct net_device *dev);
85static void ldisc_tx_wakeup(struct tty_struct *tty);
86#ifdef CONFIG_DEBUG_FS
87static inline void update_tty_status(struct ser_device *ser)
88{
89	ser->tty_status =
90		ser->tty->stopped << 5 |
91		ser->tty->flow_stopped << 3 |
92		ser->tty->packet << 2 |
93		ser->tty->port->low_latency << 1;
94}
95static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
96{
97	ser->debugfs_tty_dir = debugfs_create_dir(tty->name, debugfsdir);
98
99	debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir,
100			    &ser->tx_blob);
101
102	debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir,
103			    &ser->rx_blob);
104
105	debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir,
106			   &ser->state);
107
108	debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir,
109			  &ser->tty_status);
110
111	ser->tx_blob.data = ser->tx_data;
112	ser->tx_blob.size = 0;
113	ser->rx_blob.data = ser->rx_data;
114	ser->rx_blob.size = 0;
115}
116
117static inline void debugfs_deinit(struct ser_device *ser)
118{
119	debugfs_remove_recursive(ser->debugfs_tty_dir);
120}
121
122static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
123{
124	if (size > sizeof(ser->rx_data))
125		size = sizeof(ser->rx_data);
126	memcpy(ser->rx_data, data, size);
127	ser->rx_blob.data = ser->rx_data;
128	ser->rx_blob.size = size;
129}
130
131static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
132{
133	if (size > sizeof(ser->tx_data))
134		size = sizeof(ser->tx_data);
135	memcpy(ser->tx_data, data, size);
136	ser->tx_blob.data = ser->tx_data;
137	ser->tx_blob.size = size;
138}
139#else
140static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
141{
142}
143
144static inline void debugfs_deinit(struct ser_device *ser)
145{
146}
147
148static inline void update_tty_status(struct ser_device *ser)
149{
150}
151
152static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
153{
154}
155
156static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
157{
158}
159
160#endif
161
162static void ldisc_receive(struct tty_struct *tty, const u8 *data,
163			char *flags, int count)
164{
165	struct sk_buff *skb = NULL;
166	struct ser_device *ser;
167	int ret;
168
169	ser = tty->disc_data;
170
171	/*
172	 * NOTE: flags may contain information about break or overrun.
173	 * This is not yet handled.
174	 */
175
176
177	/*
178	 * Workaround for garbage at start of transmission,
179	 * only enable if STX handling is not enabled.
180	 */
181	if (!ser->common.use_stx && !ser->tx_started) {
182		dev_info(&ser->dev->dev,
183			"Bytes received before initial transmission -"
184			"bytes discarded.\n");
185		return;
186	}
187
188	BUG_ON(ser->dev == NULL);
189
190	/* Get a suitable caif packet and copy in data. */
191	skb = netdev_alloc_skb(ser->dev, count+1);
192	if (skb == NULL)
193		return;
194	skb_put_data(skb, data, count);
195
196	skb->protocol = htons(ETH_P_CAIF);
197	skb_reset_mac_header(skb);
198	debugfs_rx(ser, data, count);
199	/* Push received packet up the stack. */
200	ret = netif_rx_ni(skb);
201	if (!ret) {
202		ser->dev->stats.rx_packets++;
203		ser->dev->stats.rx_bytes += count;
204	} else
205		++ser->dev->stats.rx_dropped;
206	update_tty_status(ser);
207}
208
209static int handle_tx(struct ser_device *ser)
210{
211	struct tty_struct *tty;
212	struct sk_buff *skb;
213	int tty_wr, len, room;
214
215	tty = ser->tty;
216	ser->tx_started = true;
217
218	/* Enter critical section */
219	if (test_and_set_bit(CAIF_SENDING, &ser->state))
220		return 0;
221
222	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
223	while ((skb = skb_peek(&ser->head)) != NULL) {
224
225		/* Make sure you don't write too much */
226		len = skb->len;
227		room = tty_write_room(tty);
228		if (!room)
229			break;
230		if (room > ser_write_chunk)
231			room = ser_write_chunk;
232		if (len > room)
233			len = room;
234
235		/* Write to tty or loopback */
236		if (!ser_loop) {
237			tty_wr = tty->ops->write(tty, skb->data, len);
238			update_tty_status(ser);
239		} else {
240			tty_wr = len;
241			ldisc_receive(tty, skb->data, NULL, len);
242		}
243		ser->dev->stats.tx_packets++;
244		ser->dev->stats.tx_bytes += tty_wr;
245
246		/* Error on TTY ?! */
247		if (tty_wr < 0)
248			goto error;
249		/* Reduce buffer written, and discard if empty */
250		skb_pull(skb, tty_wr);
251		if (skb->len == 0) {
252			struct sk_buff *tmp = skb_dequeue(&ser->head);
253			WARN_ON(tmp != skb);
254			dev_consume_skb_any(skb);
255		}
256	}
257	/* Send flow off if queue is empty */
258	if (ser->head.qlen <= SEND_QUEUE_LOW &&
259		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
260		ser->common.flowctrl != NULL)
261				ser->common.flowctrl(ser->dev, ON);
262	clear_bit(CAIF_SENDING, &ser->state);
263	return 0;
264error:
265	clear_bit(CAIF_SENDING, &ser->state);
266	return tty_wr;
267}
268
269static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev)
270{
271	struct ser_device *ser;
272
273	ser = netdev_priv(dev);
274
275	/* Send flow off once, on high water mark */
276	if (ser->head.qlen > SEND_QUEUE_HIGH &&
277		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
278		ser->common.flowctrl != NULL)
279
280		ser->common.flowctrl(ser->dev, OFF);
281
282	skb_queue_tail(&ser->head, skb);
283	return handle_tx(ser);
284}
285
286
287static void ldisc_tx_wakeup(struct tty_struct *tty)
288{
289	struct ser_device *ser;
290
291	ser = tty->disc_data;
292	BUG_ON(ser == NULL);
293	WARN_ON(ser->tty != tty);
294	handle_tx(ser);
295}
296
297
298static void ser_release(struct work_struct *work)
299{
300	struct list_head list;
301	struct ser_device *ser, *tmp;
302
303	spin_lock(&ser_lock);
304	list_replace_init(&ser_release_list, &list);
305	spin_unlock(&ser_lock);
306
307	if (!list_empty(&list)) {
308		rtnl_lock();
309		list_for_each_entry_safe(ser, tmp, &list, node) {
310			dev_close(ser->dev);
311			unregister_netdevice(ser->dev);
312			debugfs_deinit(ser);
313		}
314		rtnl_unlock();
315	}
316}
317
318static DECLARE_WORK(ser_release_work, ser_release);
319
320static int ldisc_open(struct tty_struct *tty)
321{
322	struct ser_device *ser;
323	struct net_device *dev;
324	char name[64];
325	int result;
326
327	/* No write no play */
328	if (tty->ops->write == NULL)
329		return -EOPNOTSUPP;
330	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
331		return -EPERM;
332
333	/* release devices to avoid name collision */
334	ser_release(NULL);
335
336	result = snprintf(name, sizeof(name), "cf%s", tty->name);
337	if (result >= IFNAMSIZ)
338		return -EINVAL;
339	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
340			   caifdev_setup);
341	if (!dev)
342		return -ENOMEM;
343
344	ser = netdev_priv(dev);
345	ser->tty = tty_kref_get(tty);
346	ser->dev = dev;
347	debugfs_init(ser, tty);
348	tty->receive_room = N_TTY_BUF_SIZE;
349	tty->disc_data = ser;
350	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
351	rtnl_lock();
352	result = register_netdevice(dev);
353	if (result) {
354		tty_kref_put(tty);
355		rtnl_unlock();
356		free_netdev(dev);
357		return -ENODEV;
358	}
359
360	spin_lock(&ser_lock);
361	list_add(&ser->node, &ser_list);
362	spin_unlock(&ser_lock);
363	rtnl_unlock();
364	netif_stop_queue(dev);
365	update_tty_status(ser);
366	return 0;
367}
368
369static void ldisc_close(struct tty_struct *tty)
370{
371	struct ser_device *ser = tty->disc_data;
372
373	tty_kref_put(ser->tty);
374
375	spin_lock(&ser_lock);
376	list_move(&ser->node, &ser_release_list);
377	spin_unlock(&ser_lock);
378	schedule_work(&ser_release_work);
379}
380
381/* The line discipline structure. */
382static struct tty_ldisc_ops caif_ldisc = {
383	.owner =	THIS_MODULE,
384	.magic =	TTY_LDISC_MAGIC,
385	.name =		"n_caif",
386	.open =		ldisc_open,
387	.close =	ldisc_close,
388	.receive_buf =	ldisc_receive,
389	.write_wakeup =	ldisc_tx_wakeup
390};
391
392static int register_ldisc(void)
393{
394	int result;
395
396	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
397	if (result < 0) {
398		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
399			result);
400		return result;
401	}
402	return result;
403}
404static const struct net_device_ops netdev_ops = {
405	.ndo_open = caif_net_open,
406	.ndo_stop = caif_net_close,
407	.ndo_start_xmit = caif_xmit
408};
409
410static void caifdev_setup(struct net_device *dev)
411{
412	struct ser_device *serdev = netdev_priv(dev);
413
414	dev->features = 0;
415	dev->netdev_ops = &netdev_ops;
416	dev->type = ARPHRD_CAIF;
417	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
418	dev->mtu = CAIF_MAX_MTU;
419	dev->priv_flags |= IFF_NO_QUEUE;
420	dev->needs_free_netdev = true;
421	skb_queue_head_init(&serdev->head);
422	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
423	serdev->common.use_frag = true;
424	serdev->common.use_stx = ser_use_stx;
425	serdev->common.use_fcs = ser_use_fcs;
426	serdev->dev = dev;
427}
428
429
430static int caif_net_open(struct net_device *dev)
431{
432	netif_wake_queue(dev);
433	return 0;
434}
435
436static int caif_net_close(struct net_device *dev)
437{
438	netif_stop_queue(dev);
439	return 0;
440}
441
442static int __init caif_ser_init(void)
443{
444	int ret;
445
446	ret = register_ldisc();
447	debugfsdir = debugfs_create_dir("caif_serial", NULL);
448	return ret;
449}
450
451static void __exit caif_ser_exit(void)
452{
453	spin_lock(&ser_lock);
454	list_splice(&ser_list, &ser_release_list);
455	spin_unlock(&ser_lock);
456	ser_release(NULL);
457	cancel_work_sync(&ser_release_work);
458	tty_unregister_ldisc(N_CAIF);
459	debugfs_remove_recursive(debugfsdir);
460}
461
462module_init(caif_ser_init);
463module_exit(caif_ser_exit);
464