1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2021 STMicroelectronics - All Rights Reserved
  4 *
  5 * The rpmsg tty driver implements serial communication on the RPMsg bus to makes
  6 * possible for user-space programs to send and receive rpmsg messages as a standard
  7 * tty protocol.
  8 *
  9 * The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
 10 * The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
 11 */
 12
 13#define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt
 14
 15#include <linux/module.h>
 16#include <linux/rpmsg.h>
 17#include <linux/slab.h>
 18#include <linux/tty.h>
 19#include <linux/tty_flip.h>
 20
 21#define RPMSG_TTY_NAME	"ttyRPMSG"
 22#define MAX_TTY_RPMSG	32
 23
 24static DEFINE_IDR(tty_idr);	/* tty instance id */
 25static DEFINE_MUTEX(idr_lock);	/* protects tty_idr */
 26
 27static struct tty_driver *rpmsg_tty_driver;
 28
 29struct rpmsg_tty_port {
 30	struct tty_port		port;	 /* TTY port data */
 31	int			id;	 /* TTY rpmsg index */
 32	struct rpmsg_device	*rpdev;	 /* rpmsg device */
 33};
 34
 35static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
 36{
 37	struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
 38	int copied;
 39
 40	if (!len)
 41		return -EINVAL;
 42	copied = tty_insert_flip_string(&cport->port, data, len);
 43	if (copied != len)
 44		dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
 45	tty_flip_buffer_push(&cport->port);
 46
 47	return 0;
 48}
 49
 50static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 51{
 52	struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
 53	struct tty_port *port;
 54
 55	tty->driver_data = cport;
 56
 57	port = tty_port_get(&cport->port);
 58	return tty_port_install(port, driver, tty);
 59}
 60
 61static void rpmsg_tty_cleanup(struct tty_struct *tty)
 62{
 63	tty_port_put(tty->port);
 64}
 65
 66static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
 67{
 68	return tty_port_open(tty->port, tty, filp);
 69}
 70
 71static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
 72{
 73	return tty_port_close(tty->port, tty, filp);
 74}
 75
 76static ssize_t rpmsg_tty_write(struct tty_struct *tty, const u8 *buf,
 77			       size_t len)
 78{
 79	struct rpmsg_tty_port *cport = tty->driver_data;
 80	struct rpmsg_device *rpdev;
 81	int msg_max_size, msg_size;
 82	int ret;
 83
 84	rpdev = cport->rpdev;
 85
 86	msg_max_size = rpmsg_get_mtu(rpdev->ept);
 87	if (msg_max_size < 0)
 88		return msg_max_size;
 89
 90	msg_size = min_t(unsigned int, len, msg_max_size);
 91
 92	/*
 93	 * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
 94	 * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
 95	 */
 96	ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
 97	if (ret) {
 98		dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
 99		return ret;
100	}
101
102	return msg_size;
103}
104
105static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
106{
107	struct rpmsg_tty_port *cport = tty->driver_data;
108	int size;
109
110	size = rpmsg_get_mtu(cport->rpdev->ept);
111	if (size < 0)
112		return 0;
113
114	return size;
115}
116
117static void rpmsg_tty_hangup(struct tty_struct *tty)
118{
119	tty_port_hangup(tty->port);
120}
121
122static const struct tty_operations rpmsg_tty_ops = {
123	.install	= rpmsg_tty_install,
124	.open		= rpmsg_tty_open,
125	.close		= rpmsg_tty_close,
126	.write		= rpmsg_tty_write,
127	.write_room	= rpmsg_tty_write_room,
128	.hangup		= rpmsg_tty_hangup,
129	.cleanup	= rpmsg_tty_cleanup,
130};
131
132static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
133{
134	struct rpmsg_tty_port *cport;
135	int ret;
136
137	cport = kzalloc(sizeof(*cport), GFP_KERNEL);
138	if (!cport)
139		return ERR_PTR(-ENOMEM);
140
141	mutex_lock(&idr_lock);
142	ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
143	mutex_unlock(&idr_lock);
144
145	if (ret < 0) {
146		kfree(cport);
147		return ERR_PTR(ret);
148	}
149
150	cport->id = ret;
151
152	return cport;
153}
154
155static void rpmsg_tty_destruct_port(struct tty_port *port)
156{
157	struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port);
158
159	mutex_lock(&idr_lock);
160	idr_remove(&tty_idr, cport->id);
161	mutex_unlock(&idr_lock);
162
163	kfree(cport);
164}
165
166static const struct tty_port_operations rpmsg_tty_port_ops = {
167	.destruct = rpmsg_tty_destruct_port,
168};
169
170
171static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
172{
173	struct rpmsg_tty_port *cport;
174	struct device *dev = &rpdev->dev;
175	struct device *tty_dev;
176	int ret;
177
178	cport = rpmsg_tty_alloc_cport();
179	if (IS_ERR(cport))
180		return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
181
182	tty_port_init(&cport->port);
183	cport->port.ops = &rpmsg_tty_port_ops;
184
185	tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
186					   cport->id, dev);
187	if (IS_ERR(tty_dev)) {
188		ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
189		tty_port_put(&cport->port);
190		return ret;
191	}
192
193	cport->rpdev = rpdev;
194
195	dev_set_drvdata(dev, cport);
196
197	dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
198		rpdev->src, rpdev->dst, cport->id);
199
200	return 0;
201}
202
203static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
204{
205	struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
206
207	dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
208
209	/* User hang up to release the tty */
210	tty_port_tty_hangup(&cport->port, false);
211
212	tty_unregister_device(rpmsg_tty_driver, cport->id);
213
214	tty_port_put(&cport->port);
215}
216
217static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
218	{ .name	= "rpmsg-tty" },
219	{ },
220};
221MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
222
223static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
224	.drv.name	= KBUILD_MODNAME,
225	.id_table	= rpmsg_driver_tty_id_table,
226	.probe		= rpmsg_tty_probe,
227	.callback	= rpmsg_tty_cb,
228	.remove		= rpmsg_tty_remove,
229};
230
231static int __init rpmsg_tty_init(void)
232{
233	int ret;
234
235	rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
236					    TTY_DRIVER_DYNAMIC_DEV);
237	if (IS_ERR(rpmsg_tty_driver))
238		return PTR_ERR(rpmsg_tty_driver);
239
240	rpmsg_tty_driver->driver_name = "rpmsg_tty";
241	rpmsg_tty_driver->name = RPMSG_TTY_NAME;
242	rpmsg_tty_driver->major = 0;
243	rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
244
245	/* Disable unused mode by default */
246	rpmsg_tty_driver->init_termios = tty_std_termios;
247	rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
248	rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
249
250	tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
251
252	ret = tty_register_driver(rpmsg_tty_driver);
253	if (ret < 0) {
254		pr_err("Couldn't install driver: %d\n", ret);
255		goto error_put;
256	}
257
258	ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
259	if (ret < 0) {
260		pr_err("Couldn't register driver: %d\n", ret);
261		goto error_unregister;
262	}
263
264	return 0;
265
266error_unregister:
267	tty_unregister_driver(rpmsg_tty_driver);
268
269error_put:
270	tty_driver_kref_put(rpmsg_tty_driver);
271
272	return ret;
273}
274
275static void __exit rpmsg_tty_exit(void)
276{
277	unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
278	tty_unregister_driver(rpmsg_tty_driver);
279	tty_driver_kref_put(rpmsg_tty_driver);
280	idr_destroy(&tty_idr);
281}
282
283module_init(rpmsg_tty_init);
284module_exit(rpmsg_tty_exit);
285
286MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>");
287MODULE_DESCRIPTION("remote processor messaging tty driver");
288MODULE_LICENSE("GPL v2");