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