1/*
2 * Copyright (C) ST-Ericsson AB 2010
3 * Author:	Sjur Brendeland
4 * License terms: GNU General Public License (GPL) version 2
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, S_IRUGO);
44MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
45
46static bool ser_use_stx = true;
47module_param(ser_use_stx, bool, S_IRUGO);
48MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
49
50static bool ser_use_fcs = true;
51
52module_param(ser_use_fcs, bool, S_IRUGO);
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, S_IRUGO);
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 =
98			debugfs_create_dir(tty->name, debugfsdir);
99	if (!IS_ERR(ser->debugfs_tty_dir)) {
100		debugfs_create_blob("last_tx_msg", S_IRUSR,
101				ser->debugfs_tty_dir,
102				&ser->tx_blob);
103
104		debugfs_create_blob("last_rx_msg", S_IRUSR,
105				ser->debugfs_tty_dir,
106				&ser->rx_blob);
107
108		debugfs_create_x32("ser_state", S_IRUSR,
109				ser->debugfs_tty_dir,
110				(u32 *)&ser->state);
111
112		debugfs_create_x8("tty_status", S_IRUSR,
113				ser->debugfs_tty_dir,
114				&ser->tty_status);
115
116	}
117	ser->tx_blob.data = ser->tx_data;
118	ser->tx_blob.size = 0;
119	ser->rx_blob.data = ser->rx_data;
120	ser->rx_blob.size = 0;
121}
122
123static inline void debugfs_deinit(struct ser_device *ser)
124{
125	debugfs_remove_recursive(ser->debugfs_tty_dir);
126}
127
128static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
129{
130	if (size > sizeof(ser->rx_data))
131		size = sizeof(ser->rx_data);
132	memcpy(ser->rx_data, data, size);
133	ser->rx_blob.data = ser->rx_data;
134	ser->rx_blob.size = size;
135}
136
137static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
138{
139	if (size > sizeof(ser->tx_data))
140		size = sizeof(ser->tx_data);
141	memcpy(ser->tx_data, data, size);
142	ser->tx_blob.data = ser->tx_data;
143	ser->tx_blob.size = size;
144}
145#else
146static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
147{
148}
149
150static inline void debugfs_deinit(struct ser_device *ser)
151{
152}
153
154static inline void update_tty_status(struct ser_device *ser)
155{
156}
157
158static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
159{
160}
161
162static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
163{
164}
165
166#endif
167
168static void ldisc_receive(struct tty_struct *tty, const u8 *data,
169			char *flags, int count)
170{
171	struct sk_buff *skb = NULL;
172	struct ser_device *ser;
173	int ret;
174	u8 *p;
175
176	ser = tty->disc_data;
177
178	/*
179	 * NOTE: flags may contain information about break or overrun.
180	 * This is not yet handled.
181	 */
182
183
184	/*
185	 * Workaround for garbage at start of transmission,
186	 * only enable if STX handling is not enabled.
187	 */
188	if (!ser->common.use_stx && !ser->tx_started) {
189		dev_info(&ser->dev->dev,
190			"Bytes received before initial transmission -"
191			"bytes discarded.\n");
192		return;
193	}
194
195	BUG_ON(ser->dev == NULL);
196
197	/* Get a suitable caif packet and copy in data. */
198	skb = netdev_alloc_skb(ser->dev, count+1);
199	if (skb == NULL)
200		return;
201	p = skb_put(skb, count);
202	memcpy(p, data, count);
203
204	skb->protocol = htons(ETH_P_CAIF);
205	skb_reset_mac_header(skb);
206	debugfs_rx(ser, data, count);
207	/* Push received packet up the stack. */
208	ret = netif_rx_ni(skb);
209	if (!ret) {
210		ser->dev->stats.rx_packets++;
211		ser->dev->stats.rx_bytes += count;
212	} else
213		++ser->dev->stats.rx_dropped;
214	update_tty_status(ser);
215}
216
217static int handle_tx(struct ser_device *ser)
218{
219	struct tty_struct *tty;
220	struct sk_buff *skb;
221	int tty_wr, len, room;
222
223	tty = ser->tty;
224	ser->tx_started = true;
225
226	/* Enter critical section */
227	if (test_and_set_bit(CAIF_SENDING, &ser->state))
228		return 0;
229
230	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
231	while ((skb = skb_peek(&ser->head)) != NULL) {
232
233		/* Make sure you don't write too much */
234		len = skb->len;
235		room = tty_write_room(tty);
236		if (!room)
237			break;
238		if (room > ser_write_chunk)
239			room = ser_write_chunk;
240		if (len > room)
241			len = room;
242
243		/* Write to tty or loopback */
244		if (!ser_loop) {
245			tty_wr = tty->ops->write(tty, skb->data, len);
246			update_tty_status(ser);
247		} else {
248			tty_wr = len;
249			ldisc_receive(tty, skb->data, NULL, len);
250		}
251		ser->dev->stats.tx_packets++;
252		ser->dev->stats.tx_bytes += tty_wr;
253
254		/* Error on TTY ?! */
255		if (tty_wr < 0)
256			goto error;
257		/* Reduce buffer written, and discard if empty */
258		skb_pull(skb, tty_wr);
259		if (skb->len == 0) {
260			struct sk_buff *tmp = skb_dequeue(&ser->head);
261			WARN_ON(tmp != skb);
262			if (in_interrupt())
263				dev_kfree_skb_irq(skb);
264			else
265				kfree_skb(skb);
266		}
267	}
268	/* Send flow off if queue is empty */
269	if (ser->head.qlen <= SEND_QUEUE_LOW &&
270		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
271		ser->common.flowctrl != NULL)
272				ser->common.flowctrl(ser->dev, ON);
273	clear_bit(CAIF_SENDING, &ser->state);
274	return 0;
275error:
276	clear_bit(CAIF_SENDING, &ser->state);
277	return tty_wr;
278}
279
280static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
281{
282	struct ser_device *ser;
283
284	BUG_ON(dev == NULL);
285	ser = netdev_priv(dev);
286
287	/* Send flow off once, on high water mark */
288	if (ser->head.qlen > SEND_QUEUE_HIGH &&
289		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
290		ser->common.flowctrl != NULL)
291
292		ser->common.flowctrl(ser->dev, OFF);
293
294	skb_queue_tail(&ser->head, skb);
295	return handle_tx(ser);
296}
297
298
299static void ldisc_tx_wakeup(struct tty_struct *tty)
300{
301	struct ser_device *ser;
302
303	ser = tty->disc_data;
304	BUG_ON(ser == NULL);
305	WARN_ON(ser->tty != tty);
306	handle_tx(ser);
307}
308
309
310static void ser_release(struct work_struct *work)
311{
312	struct list_head list;
313	struct ser_device *ser, *tmp;
314
315	spin_lock(&ser_lock);
316	list_replace_init(&ser_release_list, &list);
317	spin_unlock(&ser_lock);
318
319	if (!list_empty(&list)) {
320		rtnl_lock();
321		list_for_each_entry_safe(ser, tmp, &list, node) {
322			dev_close(ser->dev);
323			unregister_netdevice(ser->dev);
324			debugfs_deinit(ser);
325		}
326		rtnl_unlock();
327	}
328}
329
330static DECLARE_WORK(ser_release_work, ser_release);
331
332static int ldisc_open(struct tty_struct *tty)
333{
334	struct ser_device *ser;
335	struct net_device *dev;
336	char name[64];
337	int result;
338
339	/* No write no play */
340	if (tty->ops->write == NULL)
341		return -EOPNOTSUPP;
342	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
343		return -EPERM;
344
345	/* release devices to avoid name collision */
346	ser_release(NULL);
347
348	result = snprintf(name, sizeof(name), "cf%s", tty->name);
349	if (result >= IFNAMSIZ)
350		return -EINVAL;
351	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
352			   caifdev_setup);
353	if (!dev)
354		return -ENOMEM;
355
356	ser = netdev_priv(dev);
357	ser->tty = tty_kref_get(tty);
358	ser->dev = dev;
359	debugfs_init(ser, tty);
360	tty->receive_room = N_TTY_BUF_SIZE;
361	tty->disc_data = ser;
362	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
363	rtnl_lock();
364	result = register_netdevice(dev);
365	if (result) {
366		rtnl_unlock();
367		free_netdev(dev);
368		return -ENODEV;
369	}
370
371	spin_lock(&ser_lock);
372	list_add(&ser->node, &ser_list);
373	spin_unlock(&ser_lock);
374	rtnl_unlock();
375	netif_stop_queue(dev);
376	update_tty_status(ser);
377	return 0;
378}
379
380static void ldisc_close(struct tty_struct *tty)
381{
382	struct ser_device *ser = tty->disc_data;
383
384	tty_kref_put(ser->tty);
385
386	spin_lock(&ser_lock);
387	list_move(&ser->node, &ser_release_list);
388	spin_unlock(&ser_lock);
389	schedule_work(&ser_release_work);
390}
391
392/* The line discipline structure. */
393static struct tty_ldisc_ops caif_ldisc = {
394	.owner =	THIS_MODULE,
395	.magic =	TTY_LDISC_MAGIC,
396	.name =		"n_caif",
397	.open =		ldisc_open,
398	.close =	ldisc_close,
399	.receive_buf =	ldisc_receive,
400	.write_wakeup =	ldisc_tx_wakeup
401};
402
403static int register_ldisc(void)
404{
405	int result;
406
407	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
408	if (result < 0) {
409		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
410			result);
411		return result;
412	}
413	return result;
414}
415static const struct net_device_ops netdev_ops = {
416	.ndo_open = caif_net_open,
417	.ndo_stop = caif_net_close,
418	.ndo_start_xmit = caif_xmit
419};
420
421static void caifdev_setup(struct net_device *dev)
422{
423	struct ser_device *serdev = netdev_priv(dev);
424
425	dev->features = 0;
426	dev->netdev_ops = &netdev_ops;
427	dev->type = ARPHRD_CAIF;
428	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
429	dev->mtu = CAIF_MAX_MTU;
430	dev->tx_queue_len = 0;
431	dev->destructor = free_netdev;
432	skb_queue_head_init(&serdev->head);
433	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
434	serdev->common.use_frag = true;
435	serdev->common.use_stx = ser_use_stx;
436	serdev->common.use_fcs = ser_use_fcs;
437	serdev->dev = dev;
438}
439
440
441static int caif_net_open(struct net_device *dev)
442{
443	netif_wake_queue(dev);
444	return 0;
445}
446
447static int caif_net_close(struct net_device *dev)
448{
449	netif_stop_queue(dev);
450	return 0;
451}
452
453static int __init caif_ser_init(void)
454{
455	int ret;
456
457	ret = register_ldisc();
458	debugfsdir = debugfs_create_dir("caif_serial", NULL);
459	return ret;
460}
461
462static void __exit caif_ser_exit(void)
463{
464	spin_lock(&ser_lock);
465	list_splice(&ser_list, &ser_release_list);
466	spin_unlock(&ser_lock);
467	ser_release(NULL);
468	cancel_work_sync(&ser_release_work);
469	tty_unregister_ldisc(N_CAIF);
470	debugfs_remove_recursive(debugfsdir);
471}
472
473module_init(caif_ser_init);
474module_exit(caif_ser_exit);
475