caif_serial.c

  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#else
130static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)
131{
132}
133
134static inline void debugfs_deinit(struct ser_device *ser)
135{
136}
137
138static inline void update_tty_status(struct ser_device *ser)
139{
140}
141
142static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size)
143{
144}
145#endif
146
147static void ldisc_receive(struct tty_struct *tty, const u8 *data,
148			  const u8 *flags, size_t count)
149{
150	struct sk_buff *skb = NULL;
151	struct ser_device *ser;
152	int ret;
153
154	ser = tty->disc_data;
155
156	/*
157	 * NOTE: flags may contain information about break or overrun.
158	 * This is not yet handled.
159	 */
160
161
162	/*
163	 * Workaround for garbage at start of transmission,
164	 * only enable if STX handling is not enabled.
165	 */
166	if (!ser->common.use_stx && !ser->tx_started) {
167		dev_info(&ser->dev->dev,
168			"Bytes received before initial transmission -"
169			"bytes discarded.\n");
170		return;
171	}
172
173	BUG_ON(ser->dev == NULL);
174
175	/* Get a suitable caif packet and copy in data. */
176	skb = netdev_alloc_skb(ser->dev, count+1);
177	if (skb == NULL)
178		return;
179	skb_put_data(skb, data, count);
180
181	skb->protocol = htons(ETH_P_CAIF);
182	skb_reset_mac_header(skb);
183	debugfs_rx(ser, data, count);
184	/* Push received packet up the stack. */
185	ret = netif_rx(skb);
186	if (!ret) {
187		ser->dev->stats.rx_packets++;
188		ser->dev->stats.rx_bytes += count;
189	} else
190		++ser->dev->stats.rx_dropped;
191	update_tty_status(ser);
192}
193
194static int handle_tx(struct ser_device *ser)
195{
196	struct tty_struct *tty;
197	struct sk_buff *skb;
198	int tty_wr, len, room;
199
200	tty = ser->tty;
201	ser->tx_started = true;
202
203	/* Enter critical section */
204	if (test_and_set_bit(CAIF_SENDING, &ser->state))
205		return 0;
206
207	/* skb_peek is safe because handle_tx is called after skb_queue_tail */
208	while ((skb = skb_peek(&ser->head)) != NULL) {
209
210		/* Make sure you don't write too much */
211		len = skb->len;
212		room = tty_write_room(tty);
213		if (!room)
214			break;
215		if (room > ser_write_chunk)
216			room = ser_write_chunk;
217		if (len > room)
218			len = room;
219
220		/* Write to tty or loopback */
221		if (!ser_loop) {
222			tty_wr = tty->ops->write(tty, skb->data, len);
223			update_tty_status(ser);
224		} else {
225			tty_wr = len;
226			ldisc_receive(tty, skb->data, NULL, len);
227		}
228		ser->dev->stats.tx_packets++;
229		ser->dev->stats.tx_bytes += tty_wr;
230
231		/* Error on TTY ?! */
232		if (tty_wr < 0)
233			goto error;
234		/* Reduce buffer written, and discard if empty */
235		skb_pull(skb, tty_wr);
236		if (skb->len == 0) {
237			struct sk_buff *tmp = skb_dequeue(&ser->head);
238			WARN_ON(tmp != skb);
239			dev_consume_skb_any(skb);
240		}
241	}
242	/* Send flow off if queue is empty */
243	if (ser->head.qlen <= SEND_QUEUE_LOW &&
244		test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
245		ser->common.flowctrl != NULL)
246				ser->common.flowctrl(ser->dev, ON);
247	clear_bit(CAIF_SENDING, &ser->state);
248	return 0;
249error:
250	clear_bit(CAIF_SENDING, &ser->state);
251	return tty_wr;
252}
253
254static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev)
255{
256	struct ser_device *ser;
257
258	ser = netdev_priv(dev);
259
260	/* Send flow off once, on high water mark */
261	if (ser->head.qlen > SEND_QUEUE_HIGH &&
262		!test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
263		ser->common.flowctrl != NULL)
264
265		ser->common.flowctrl(ser->dev, OFF);
266
267	skb_queue_tail(&ser->head, skb);
268	return handle_tx(ser);
269}
270
271
272static void ldisc_tx_wakeup(struct tty_struct *tty)
273{
274	struct ser_device *ser;
275
276	ser = tty->disc_data;
277	BUG_ON(ser == NULL);
278	WARN_ON(ser->tty != tty);
279	handle_tx(ser);
280}
281
282
283static void ser_release(struct work_struct *work)
284{
285	struct list_head list;
286	struct ser_device *ser, *tmp;
287	struct tty_struct *tty;
288
289	spin_lock(&ser_lock);
290	list_replace_init(&ser_release_list, &list);
291	spin_unlock(&ser_lock);
292
293	if (!list_empty(&list)) {
294		rtnl_lock();
295		list_for_each_entry_safe(ser, tmp, &list, node) {
296			tty = ser->tty;
297			dev_close(ser->dev);
298			unregister_netdevice(ser->dev);
299			debugfs_deinit(ser);
300			tty_kref_put(tty->link);
301			tty_kref_put(tty);
302		}
303		rtnl_unlock();
304	}
305}
306
307static DECLARE_WORK(ser_release_work, ser_release);
308
309static int ldisc_open(struct tty_struct *tty)
310{
311	struct ser_device *ser;
312	struct net_device *dev;
313	char name[64];
314	int result;
315
316	/* No write no play */
317	if (tty->ops->write == NULL)
318		return -EOPNOTSUPP;
319	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
320		return -EPERM;
321
322	/* release devices to avoid name collision */
323	ser_release(NULL);
324
325	result = snprintf(name, sizeof(name), "cf%s", tty->name);
326	if (result >= IFNAMSIZ)
327		return -EINVAL;
328	dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
329			   caifdev_setup);
330	if (!dev)
331		return -ENOMEM;
332
333	ser = netdev_priv(dev);
334	ser->tty = tty_kref_get(tty);
335	tty_kref_get(tty->link);
336	ser->dev = dev;
337	debugfs_init(ser, tty);
338	tty->receive_room = 4096;
339	tty->disc_data = ser;
340	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
341	rtnl_lock();
342	result = register_netdevice(dev);
343	if (result) {
344		tty_kref_put(tty->link);
345		tty_kref_put(tty);
346		rtnl_unlock();
347		free_netdev(dev);
348		return -ENODEV;
349	}
350
351	spin_lock(&ser_lock);
352	list_add(&ser->node, &ser_list);
353	spin_unlock(&ser_lock);
354	rtnl_unlock();
355	netif_stop_queue(dev);
356	update_tty_status(ser);
357	return 0;
358}
359
360static void ldisc_close(struct tty_struct *tty)
361{
362	struct ser_device *ser = tty->disc_data;
363
364	spin_lock(&ser_lock);
365	list_move(&ser->node, &ser_release_list);
366	spin_unlock(&ser_lock);
367	schedule_work(&ser_release_work);
368}
369
370/* The line discipline structure. */
371static struct tty_ldisc_ops caif_ldisc = {
372	.owner =	THIS_MODULE,
373	.num =		N_CAIF,
374	.name =		"n_caif",
375	.open =		ldisc_open,
376	.close =	ldisc_close,
377	.receive_buf =	ldisc_receive,
378	.write_wakeup =	ldisc_tx_wakeup
379};
380
381static const struct net_device_ops netdev_ops = {
382	.ndo_open = caif_net_open,
383	.ndo_stop = caif_net_close,
384	.ndo_start_xmit = caif_xmit
385};
386
387static void caifdev_setup(struct net_device *dev)
388{
389	struct ser_device *serdev = netdev_priv(dev);
390
391	dev->features = 0;
392	dev->netdev_ops = &netdev_ops;
393	dev->type = ARPHRD_CAIF;
394	dev->flags = IFF_POINTOPOINT | IFF_NOARP;
395	dev->mtu = CAIF_MAX_MTU;
396	dev->priv_flags |= IFF_NO_QUEUE;
397	dev->needs_free_netdev = true;
398	skb_queue_head_init(&serdev->head);
399	serdev->common.link_select = CAIF_LINK_LOW_LATENCY;
400	serdev->common.use_frag = true;
401	serdev->common.use_stx = ser_use_stx;
402	serdev->common.use_fcs = ser_use_fcs;
403	serdev->dev = dev;
404}
405
406
407static int caif_net_open(struct net_device *dev)
408{
409	netif_wake_queue(dev);
410	return 0;
411}
412
413static int caif_net_close(struct net_device *dev)
414{
415	netif_stop_queue(dev);
416	return 0;
417}
418
419static int __init caif_ser_init(void)
420{
421	int ret;
422
423	ret = tty_register_ldisc(&caif_ldisc);
424	if (ret < 0)
425		pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, ret);
426
427	debugfsdir = debugfs_create_dir("caif_serial", NULL);
428	return ret;
429}
430
431static void __exit caif_ser_exit(void)
432{
433	spin_lock(&ser_lock);
434	list_splice(&ser_list, &ser_release_list);
435	spin_unlock(&ser_lock);
436	ser_release(NULL);
437	cancel_work_sync(&ser_release_work);
438	tty_unregister_ldisc(&caif_ldisc);
439	debugfs_remove_recursive(debugfsdir);
440}
441
442module_init(caif_ser_init);
443module_exit(caif_ser_exit);