1/*
2 * Copyright (C) ST-Ericsson AB 2010
3 * Author:	Sjur Brendeland / sjur.brandeland@stericsson.com
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<sjur.brandeland@stericsson.com>");
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
38/*This list is protected by the rtnl lock. */
39static LIST_HEAD(ser_list);
40
41static bool ser_loop;
42module_param(ser_loop, bool, S_IRUGO);
43MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode.");
44
45static bool ser_use_stx = true;
46module_param(ser_use_stx, bool, S_IRUGO);
47MODULE_PARM_DESC(ser_use_stx, "STX enabled or not.");
48
49static bool ser_use_fcs = true;
50
51module_param(ser_use_fcs, bool, S_IRUGO);
52MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not.");
53
54static int ser_write_chunk = MAX_WRITE_CHUNK;
55module_param(ser_write_chunk, int, S_IRUGO);
56
57MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART.");
58
59static struct dentry *debugfsdir;
60
61static int caif_net_open(struct net_device *dev);
62static int caif_net_close(struct net_device *dev);
63
64struct ser_device {
65	struct caif_dev_common common;
66	struct list_head node;
67	struct net_device *dev;
68	struct sk_buff_head head;
69	struct tty_struct *tty;
70	bool tx_started;
71	unsigned long state;
72	char *tty_name;
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->hw_stopped << 4 |
92		ser->tty->flow_stopped << 3 |
93		ser->tty->packet << 2 |
94		ser->tty->low_latency << 1 |
95		ser->tty->warned;
96}
97static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
98{
99	ser->debugfs_tty_dir =
100			debugfs_create_dir(tty->name, debugfsdir);
101	if (!IS_ERR(ser->debugfs_tty_dir)) {
102		debugfs_create_blob("last_tx_msg", S_IRUSR,
103				ser->debugfs_tty_dir,
104				&ser->tx_blob);
105
106		debugfs_create_blob("last_rx_msg", S_IRUSR,
107				ser->debugfs_tty_dir,
108				&ser->rx_blob);
109
110		debugfs_create_x32("ser_state", S_IRUSR,
111				ser->debugfs_tty_dir,
112				(u32 *)&ser->state);
113
114		debugfs_create_x8("tty_status", S_IRUSR,
115				ser->debugfs_tty_dir,
116				&ser->tty_status);
117
118	}
119	ser->tx_blob.data = ser->tx_data;
120	ser->tx_blob.size = 0;
121	ser->rx_blob.data = ser->rx_data;
122	ser->rx_blob.size = 0;
123}
124
125static inline void debugfs_deinit(struct ser_device *ser)
126{
127	debugfs_remove_recursive(ser->debugfs_tty_dir);
128}
129
130static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
131{
132	if (size > sizeof(ser->rx_data))
133		size = sizeof(ser->rx_data);
134	memcpy(ser->rx_data, data, size);
135	ser->rx_blob.data = ser->rx_data;
136	ser->rx_blob.size = size;
137}
138
139static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
140{
141	if (size > sizeof(ser->tx_data))
142		size = sizeof(ser->tx_data);
143	memcpy(ser->tx_data, data, size);
144	ser->tx_blob.data = ser->tx_data;
145	ser->tx_blob.size = size;
146}
147#else
148static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
149{
150}
151
152static inline void debugfs_deinit(struct ser_device *ser)
153{
154}
155
156static inline void update_tty_status(struct ser_device *ser)
157{
158}
159
160static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
161{
162}
163
164static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size)
165{
166}
167
168#endif
169
170static void ldisc_receive(struct tty_struct *tty, const u8 *data,
171			char *flags, int count)
172{
173	struct sk_buff *skb = NULL;
174	struct ser_device *ser;
175	int ret;
176	u8 *p;
177
178	ser = tty->disc_data;
179
180	/*
181	 * NOTE: flags may contain information about break or overrun.
182	 * This is not yet handled.
183	 */
184
185
186	/*
187	 * Workaround for garbage at start of transmission,
188	 * only enable if STX handling is not enabled.
189	 */
190	if (!ser->common.use_stx && !ser->tx_started) {
191		dev_info(&ser->dev->dev,
192			"Bytes received before initial transmission -"
193			"bytes discarded.\n");
194		return;
195	}
196
197	BUG_ON(ser->dev == NULL);
198
199	/* Get a suitable caif packet and copy in data. */
200	skb = netdev_alloc_skb(ser->dev, count+1);
201	if (skb == NULL)
202		return;
203	p = skb_put(skb, count);
204	memcpy(p, data, count);
205
206	skb->protocol = htons(ETH_P_CAIF);
207	skb_reset_mac_header(skb);
208	skb->dev = ser->dev;
209	debugfs_rx(ser, data, count);
210	/* Push received packet up the stack. */
211	ret = netif_rx_ni(skb);
212	if (!ret) {
213		ser->dev->stats.rx_packets++;
214		ser->dev->stats.rx_bytes += count;
215	} else
216		++ser->dev->stats.rx_dropped;
217	update_tty_status(ser);
218}
219
220static int handle_tx(struct ser_device *ser)
221{
222	struct tty_struct *tty;
223	struct sk_buff *skb;
224	int tty_wr, len, room;
225
226	tty = ser->tty;
227	ser->tx_started = true;
228
229	/* Enter critical section */
230	if (test_and_set_bit(CAIF_SENDING, &ser->state))
231		return 0;
232
233	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
234	while ((skb = skb_peek(&ser->head)) != NULL) {
235
236		/* Make sure you don't write too much */
237		len = skb->len;
238		room = tty_write_room(tty);
239		if (!room)
240			break;
241		if (room > ser_write_chunk)
242			room = ser_write_chunk;
243		if (len > room)
244			len = room;
245
246		/* Write to tty or loopback */
247		if (!ser_loop) {
248			tty_wr = tty->ops->write(tty, skb->data, len);
249			update_tty_status(ser);
250		} else {
251			tty_wr = len;
252			ldisc_receive(tty, skb->data, NULL, len);
253		}
254		ser->dev->stats.tx_packets++;
255		ser->dev->stats.tx_bytes += tty_wr;
256
257		/* Error on TTY ?! */
258		if (tty_wr < 0)
259			goto error;
260		/* Reduce buffer written, and discard if empty */
261		skb_pull(skb, tty_wr);
262		if (skb->len == 0) {
263			struct sk_buff *tmp = skb_dequeue(&ser->head);
264			WARN_ON(tmp != skb);
265			if (in_interrupt())
266				dev_kfree_skb_irq(skb);
267			else
268				kfree_skb(skb);
269		}
270	}
271	/* Send flow off if queue is empty */
272	if (ser->head.qlen <= SEND_QUEUE_LOW &&
273		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
274		ser->common.flowctrl != NULL)
275				ser->common.flowctrl(ser->dev, ON);
276	clear_bit(CAIF_SENDING, &ser->state);
277	return 0;
278error:
279	clear_bit(CAIF_SENDING, &ser->state);
280	return tty_wr;
281}
282
283static int caif_xmit(struct sk_buff *skb, struct net_device *dev)
284{
285	struct ser_device *ser;
286
287	BUG_ON(dev == NULL);
288	ser = netdev_priv(dev);
289
290	/* Send flow off once, on high water mark */
291	if (ser->head.qlen > SEND_QUEUE_HIGH &&
292		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
293		ser->common.flowctrl != NULL)
294
295		ser->common.flowctrl(ser->dev, OFF);
296
297	skb_queue_tail(&ser->head, skb);
298	return handle_tx(ser);
299}
300
301
302static void ldisc_tx_wakeup(struct tty_struct *tty)
303{
304	struct ser_device *ser;
305
306	ser = tty->disc_data;
307	BUG_ON(ser == NULL);
308	WARN_ON(ser->tty != tty);
309	handle_tx(ser);
310}
311
312
313static int ldisc_open(struct tty_struct *tty)
314{
315	struct ser_device *ser;
316	struct net_device *dev;
317	char name[64];
318	int result;
319
320	/* No write no play */
321	if (tty->ops->write == NULL)
322		return -EOPNOTSUPP;
323	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
324		return -EPERM;
325
326	sprintf(name, "cf%s", tty->name);
327	dev = alloc_netdev(sizeof(*ser), name, caifdev_setup);
328	ser = netdev_priv(dev);
329	ser->tty = tty_kref_get(tty);
330	ser->dev = dev;
331	debugfs_init(ser, tty);
332	tty->receive_room = N_TTY_BUF_SIZE;
333	tty->disc_data = ser;
334	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
335	rtnl_lock();
336	result = register_netdevice(dev);
337	if (result) {
338		rtnl_unlock();
339		free_netdev(dev);
340		return -ENODEV;
341	}
342
343	list_add(&ser->node, &ser_list);
344	rtnl_unlock();
345	netif_stop_queue(dev);
346	update_tty_status(ser);
347	return 0;
348}
349
350static void ldisc_close(struct tty_struct *tty)
351{
352	struct ser_device *ser = tty->disc_data;
353	/* Remove may be called inside or outside of rtnl_lock */
354	int islocked = rtnl_is_locked();
355
356	if (!islocked)
357		rtnl_lock();
358	/* device is freed automagically by net-sysfs */
359	dev_close(ser->dev);
360	unregister_netdevice(ser->dev);
361	list_del(&ser->node);
362	debugfs_deinit(ser);
363	tty_kref_put(ser->tty);
364	if (!islocked)
365		rtnl_unlock();
366}
367
368/* The line discipline structure. */
369static struct tty_ldisc_ops caif_ldisc = {
370	.owner =	THIS_MODULE,
371	.magic =	TTY_LDISC_MAGIC,
372	.name =		"n_caif",
373	.open =		ldisc_open,
374	.close =	ldisc_close,
375	.receive_buf =	ldisc_receive,
376	.write_wakeup =	ldisc_tx_wakeup
377};
378
379static int register_ldisc(void)
380{
381	int result;
382
383	result = tty_register_ldisc(N_CAIF, &caif_ldisc);
384	if (result < 0) {
385		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF,
386			result);
387		return result;
388	}
389	return result;
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->tx_queue_len = 0;
407	dev->destructor = free_netdev;
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 = register_ldisc();
434	debugfsdir = debugfs_create_dir("caif_serial", NULL);
435	return ret;
436}
437
438static void __exit caif_ser_exit(void)
439{
440	struct ser_device *ser = NULL;
441	struct list_head *node;
442	struct list_head *_tmp;
443
444	list_for_each_safe(node, _tmp, &ser_list) {
445		ser = list_entry(node, struct ser_device, node);
446		dev_close(ser->dev);
447		unregister_netdevice(ser->dev);
448		list_del(node);
449	}
450	tty_unregister_ldisc(N_CAIF);
451	debugfs_remove_recursive(debugfsdir);
452}
453
454module_init(caif_ser_init);
455module_exit(caif_ser_exit);
456