162306a36Sopenharmony_ci// SPDX-License-Identifier: GPL-2.0
262306a36Sopenharmony_ci/*
362306a36Sopenharmony_ci * Copyright (C) 2021 STMicroelectronics - All Rights Reserved
462306a36Sopenharmony_ci *
562306a36Sopenharmony_ci * The rpmsg tty driver implements serial communication on the RPMsg bus to makes
662306a36Sopenharmony_ci * possible for user-space programs to send and receive rpmsg messages as a standard
762306a36Sopenharmony_ci * tty protocol.
862306a36Sopenharmony_ci *
962306a36Sopenharmony_ci * The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
1062306a36Sopenharmony_ci * The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
1162306a36Sopenharmony_ci */
1262306a36Sopenharmony_ci
1362306a36Sopenharmony_ci#define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt
1462306a36Sopenharmony_ci
1562306a36Sopenharmony_ci#include <linux/module.h>
1662306a36Sopenharmony_ci#include <linux/rpmsg.h>
1762306a36Sopenharmony_ci#include <linux/slab.h>
1862306a36Sopenharmony_ci#include <linux/tty.h>
1962306a36Sopenharmony_ci#include <linux/tty_flip.h>
2062306a36Sopenharmony_ci
2162306a36Sopenharmony_ci#define RPMSG_TTY_NAME	"ttyRPMSG"
2262306a36Sopenharmony_ci#define MAX_TTY_RPMSG	32
2362306a36Sopenharmony_ci
2462306a36Sopenharmony_cistatic DEFINE_IDR(tty_idr);	/* tty instance id */
2562306a36Sopenharmony_cistatic DEFINE_MUTEX(idr_lock);	/* protects tty_idr */
2662306a36Sopenharmony_ci
2762306a36Sopenharmony_cistatic struct tty_driver *rpmsg_tty_driver;
2862306a36Sopenharmony_ci
2962306a36Sopenharmony_cistruct rpmsg_tty_port {
3062306a36Sopenharmony_ci	struct tty_port		port;	 /* TTY port data */
3162306a36Sopenharmony_ci	int			id;	 /* TTY rpmsg index */
3262306a36Sopenharmony_ci	struct rpmsg_device	*rpdev;	 /* rpmsg device */
3362306a36Sopenharmony_ci};
3462306a36Sopenharmony_ci
3562306a36Sopenharmony_cistatic int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
3662306a36Sopenharmony_ci{
3762306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
3862306a36Sopenharmony_ci	int copied;
3962306a36Sopenharmony_ci
4062306a36Sopenharmony_ci	if (!len)
4162306a36Sopenharmony_ci		return -EINVAL;
4262306a36Sopenharmony_ci	copied = tty_insert_flip_string(&cport->port, data, len);
4362306a36Sopenharmony_ci	if (copied != len)
4462306a36Sopenharmony_ci		dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
4562306a36Sopenharmony_ci	tty_flip_buffer_push(&cport->port);
4662306a36Sopenharmony_ci
4762306a36Sopenharmony_ci	return 0;
4862306a36Sopenharmony_ci}
4962306a36Sopenharmony_ci
5062306a36Sopenharmony_cistatic int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
5162306a36Sopenharmony_ci{
5262306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
5362306a36Sopenharmony_ci	struct tty_port *port;
5462306a36Sopenharmony_ci
5562306a36Sopenharmony_ci	tty->driver_data = cport;
5662306a36Sopenharmony_ci
5762306a36Sopenharmony_ci	port = tty_port_get(&cport->port);
5862306a36Sopenharmony_ci	return tty_port_install(port, driver, tty);
5962306a36Sopenharmony_ci}
6062306a36Sopenharmony_ci
6162306a36Sopenharmony_cistatic void rpmsg_tty_cleanup(struct tty_struct *tty)
6262306a36Sopenharmony_ci{
6362306a36Sopenharmony_ci	tty_port_put(tty->port);
6462306a36Sopenharmony_ci}
6562306a36Sopenharmony_ci
6662306a36Sopenharmony_cistatic int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
6762306a36Sopenharmony_ci{
6862306a36Sopenharmony_ci	return tty_port_open(tty->port, tty, filp);
6962306a36Sopenharmony_ci}
7062306a36Sopenharmony_ci
7162306a36Sopenharmony_cistatic void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
7262306a36Sopenharmony_ci{
7362306a36Sopenharmony_ci	return tty_port_close(tty->port, tty, filp);
7462306a36Sopenharmony_ci}
7562306a36Sopenharmony_ci
7662306a36Sopenharmony_cistatic ssize_t rpmsg_tty_write(struct tty_struct *tty, const u8 *buf,
7762306a36Sopenharmony_ci			       size_t len)
7862306a36Sopenharmony_ci{
7962306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = tty->driver_data;
8062306a36Sopenharmony_ci	struct rpmsg_device *rpdev;
8162306a36Sopenharmony_ci	int msg_max_size, msg_size;
8262306a36Sopenharmony_ci	int ret;
8362306a36Sopenharmony_ci
8462306a36Sopenharmony_ci	rpdev = cport->rpdev;
8562306a36Sopenharmony_ci
8662306a36Sopenharmony_ci	msg_max_size = rpmsg_get_mtu(rpdev->ept);
8762306a36Sopenharmony_ci	if (msg_max_size < 0)
8862306a36Sopenharmony_ci		return msg_max_size;
8962306a36Sopenharmony_ci
9062306a36Sopenharmony_ci	msg_size = min_t(unsigned int, len, msg_max_size);
9162306a36Sopenharmony_ci
9262306a36Sopenharmony_ci	/*
9362306a36Sopenharmony_ci	 * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
9462306a36Sopenharmony_ci	 * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
9562306a36Sopenharmony_ci	 */
9662306a36Sopenharmony_ci	ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
9762306a36Sopenharmony_ci	if (ret) {
9862306a36Sopenharmony_ci		dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
9962306a36Sopenharmony_ci		return ret;
10062306a36Sopenharmony_ci	}
10162306a36Sopenharmony_ci
10262306a36Sopenharmony_ci	return msg_size;
10362306a36Sopenharmony_ci}
10462306a36Sopenharmony_ci
10562306a36Sopenharmony_cistatic unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
10662306a36Sopenharmony_ci{
10762306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = tty->driver_data;
10862306a36Sopenharmony_ci	int size;
10962306a36Sopenharmony_ci
11062306a36Sopenharmony_ci	size = rpmsg_get_mtu(cport->rpdev->ept);
11162306a36Sopenharmony_ci	if (size < 0)
11262306a36Sopenharmony_ci		return 0;
11362306a36Sopenharmony_ci
11462306a36Sopenharmony_ci	return size;
11562306a36Sopenharmony_ci}
11662306a36Sopenharmony_ci
11762306a36Sopenharmony_cistatic void rpmsg_tty_hangup(struct tty_struct *tty)
11862306a36Sopenharmony_ci{
11962306a36Sopenharmony_ci	tty_port_hangup(tty->port);
12062306a36Sopenharmony_ci}
12162306a36Sopenharmony_ci
12262306a36Sopenharmony_cistatic const struct tty_operations rpmsg_tty_ops = {
12362306a36Sopenharmony_ci	.install	= rpmsg_tty_install,
12462306a36Sopenharmony_ci	.open		= rpmsg_tty_open,
12562306a36Sopenharmony_ci	.close		= rpmsg_tty_close,
12662306a36Sopenharmony_ci	.write		= rpmsg_tty_write,
12762306a36Sopenharmony_ci	.write_room	= rpmsg_tty_write_room,
12862306a36Sopenharmony_ci	.hangup		= rpmsg_tty_hangup,
12962306a36Sopenharmony_ci	.cleanup	= rpmsg_tty_cleanup,
13062306a36Sopenharmony_ci};
13162306a36Sopenharmony_ci
13262306a36Sopenharmony_cistatic struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
13362306a36Sopenharmony_ci{
13462306a36Sopenharmony_ci	struct rpmsg_tty_port *cport;
13562306a36Sopenharmony_ci	int ret;
13662306a36Sopenharmony_ci
13762306a36Sopenharmony_ci	cport = kzalloc(sizeof(*cport), GFP_KERNEL);
13862306a36Sopenharmony_ci	if (!cport)
13962306a36Sopenharmony_ci		return ERR_PTR(-ENOMEM);
14062306a36Sopenharmony_ci
14162306a36Sopenharmony_ci	mutex_lock(&idr_lock);
14262306a36Sopenharmony_ci	ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
14362306a36Sopenharmony_ci	mutex_unlock(&idr_lock);
14462306a36Sopenharmony_ci
14562306a36Sopenharmony_ci	if (ret < 0) {
14662306a36Sopenharmony_ci		kfree(cport);
14762306a36Sopenharmony_ci		return ERR_PTR(ret);
14862306a36Sopenharmony_ci	}
14962306a36Sopenharmony_ci
15062306a36Sopenharmony_ci	cport->id = ret;
15162306a36Sopenharmony_ci
15262306a36Sopenharmony_ci	return cport;
15362306a36Sopenharmony_ci}
15462306a36Sopenharmony_ci
15562306a36Sopenharmony_cistatic void rpmsg_tty_destruct_port(struct tty_port *port)
15662306a36Sopenharmony_ci{
15762306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port);
15862306a36Sopenharmony_ci
15962306a36Sopenharmony_ci	mutex_lock(&idr_lock);
16062306a36Sopenharmony_ci	idr_remove(&tty_idr, cport->id);
16162306a36Sopenharmony_ci	mutex_unlock(&idr_lock);
16262306a36Sopenharmony_ci
16362306a36Sopenharmony_ci	kfree(cport);
16462306a36Sopenharmony_ci}
16562306a36Sopenharmony_ci
16662306a36Sopenharmony_cistatic const struct tty_port_operations rpmsg_tty_port_ops = {
16762306a36Sopenharmony_ci	.destruct = rpmsg_tty_destruct_port,
16862306a36Sopenharmony_ci};
16962306a36Sopenharmony_ci
17062306a36Sopenharmony_ci
17162306a36Sopenharmony_cistatic int rpmsg_tty_probe(struct rpmsg_device *rpdev)
17262306a36Sopenharmony_ci{
17362306a36Sopenharmony_ci	struct rpmsg_tty_port *cport;
17462306a36Sopenharmony_ci	struct device *dev = &rpdev->dev;
17562306a36Sopenharmony_ci	struct device *tty_dev;
17662306a36Sopenharmony_ci	int ret;
17762306a36Sopenharmony_ci
17862306a36Sopenharmony_ci	cport = rpmsg_tty_alloc_cport();
17962306a36Sopenharmony_ci	if (IS_ERR(cport))
18062306a36Sopenharmony_ci		return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
18162306a36Sopenharmony_ci
18262306a36Sopenharmony_ci	tty_port_init(&cport->port);
18362306a36Sopenharmony_ci	cport->port.ops = &rpmsg_tty_port_ops;
18462306a36Sopenharmony_ci
18562306a36Sopenharmony_ci	tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
18662306a36Sopenharmony_ci					   cport->id, dev);
18762306a36Sopenharmony_ci	if (IS_ERR(tty_dev)) {
18862306a36Sopenharmony_ci		ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
18962306a36Sopenharmony_ci		tty_port_put(&cport->port);
19062306a36Sopenharmony_ci		return ret;
19162306a36Sopenharmony_ci	}
19262306a36Sopenharmony_ci
19362306a36Sopenharmony_ci	cport->rpdev = rpdev;
19462306a36Sopenharmony_ci
19562306a36Sopenharmony_ci	dev_set_drvdata(dev, cport);
19662306a36Sopenharmony_ci
19762306a36Sopenharmony_ci	dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
19862306a36Sopenharmony_ci		rpdev->src, rpdev->dst, cport->id);
19962306a36Sopenharmony_ci
20062306a36Sopenharmony_ci	return 0;
20162306a36Sopenharmony_ci}
20262306a36Sopenharmony_ci
20362306a36Sopenharmony_cistatic void rpmsg_tty_remove(struct rpmsg_device *rpdev)
20462306a36Sopenharmony_ci{
20562306a36Sopenharmony_ci	struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
20662306a36Sopenharmony_ci
20762306a36Sopenharmony_ci	dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
20862306a36Sopenharmony_ci
20962306a36Sopenharmony_ci	/* User hang up to release the tty */
21062306a36Sopenharmony_ci	tty_port_tty_hangup(&cport->port, false);
21162306a36Sopenharmony_ci
21262306a36Sopenharmony_ci	tty_unregister_device(rpmsg_tty_driver, cport->id);
21362306a36Sopenharmony_ci
21462306a36Sopenharmony_ci	tty_port_put(&cport->port);
21562306a36Sopenharmony_ci}
21662306a36Sopenharmony_ci
21762306a36Sopenharmony_cistatic struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
21862306a36Sopenharmony_ci	{ .name	= "rpmsg-tty" },
21962306a36Sopenharmony_ci	{ },
22062306a36Sopenharmony_ci};
22162306a36Sopenharmony_ciMODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
22262306a36Sopenharmony_ci
22362306a36Sopenharmony_cistatic struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
22462306a36Sopenharmony_ci	.drv.name	= KBUILD_MODNAME,
22562306a36Sopenharmony_ci	.id_table	= rpmsg_driver_tty_id_table,
22662306a36Sopenharmony_ci	.probe		= rpmsg_tty_probe,
22762306a36Sopenharmony_ci	.callback	= rpmsg_tty_cb,
22862306a36Sopenharmony_ci	.remove		= rpmsg_tty_remove,
22962306a36Sopenharmony_ci};
23062306a36Sopenharmony_ci
23162306a36Sopenharmony_cistatic int __init rpmsg_tty_init(void)
23262306a36Sopenharmony_ci{
23362306a36Sopenharmony_ci	int ret;
23462306a36Sopenharmony_ci
23562306a36Sopenharmony_ci	rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
23662306a36Sopenharmony_ci					    TTY_DRIVER_DYNAMIC_DEV);
23762306a36Sopenharmony_ci	if (IS_ERR(rpmsg_tty_driver))
23862306a36Sopenharmony_ci		return PTR_ERR(rpmsg_tty_driver);
23962306a36Sopenharmony_ci
24062306a36Sopenharmony_ci	rpmsg_tty_driver->driver_name = "rpmsg_tty";
24162306a36Sopenharmony_ci	rpmsg_tty_driver->name = RPMSG_TTY_NAME;
24262306a36Sopenharmony_ci	rpmsg_tty_driver->major = 0;
24362306a36Sopenharmony_ci	rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
24462306a36Sopenharmony_ci
24562306a36Sopenharmony_ci	/* Disable unused mode by default */
24662306a36Sopenharmony_ci	rpmsg_tty_driver->init_termios = tty_std_termios;
24762306a36Sopenharmony_ci	rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
24862306a36Sopenharmony_ci	rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
24962306a36Sopenharmony_ci
25062306a36Sopenharmony_ci	tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
25162306a36Sopenharmony_ci
25262306a36Sopenharmony_ci	ret = tty_register_driver(rpmsg_tty_driver);
25362306a36Sopenharmony_ci	if (ret < 0) {
25462306a36Sopenharmony_ci		pr_err("Couldn't install driver: %d\n", ret);
25562306a36Sopenharmony_ci		goto error_put;
25662306a36Sopenharmony_ci	}
25762306a36Sopenharmony_ci
25862306a36Sopenharmony_ci	ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
25962306a36Sopenharmony_ci	if (ret < 0) {
26062306a36Sopenharmony_ci		pr_err("Couldn't register driver: %d\n", ret);
26162306a36Sopenharmony_ci		goto error_unregister;
26262306a36Sopenharmony_ci	}
26362306a36Sopenharmony_ci
26462306a36Sopenharmony_ci	return 0;
26562306a36Sopenharmony_ci
26662306a36Sopenharmony_cierror_unregister:
26762306a36Sopenharmony_ci	tty_unregister_driver(rpmsg_tty_driver);
26862306a36Sopenharmony_ci
26962306a36Sopenharmony_cierror_put:
27062306a36Sopenharmony_ci	tty_driver_kref_put(rpmsg_tty_driver);
27162306a36Sopenharmony_ci
27262306a36Sopenharmony_ci	return ret;
27362306a36Sopenharmony_ci}
27462306a36Sopenharmony_ci
27562306a36Sopenharmony_cistatic void __exit rpmsg_tty_exit(void)
27662306a36Sopenharmony_ci{
27762306a36Sopenharmony_ci	unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
27862306a36Sopenharmony_ci	tty_unregister_driver(rpmsg_tty_driver);
27962306a36Sopenharmony_ci	tty_driver_kref_put(rpmsg_tty_driver);
28062306a36Sopenharmony_ci	idr_destroy(&tty_idr);
28162306a36Sopenharmony_ci}
28262306a36Sopenharmony_ci
28362306a36Sopenharmony_cimodule_init(rpmsg_tty_init);
28462306a36Sopenharmony_cimodule_exit(rpmsg_tty_exit);
28562306a36Sopenharmony_ci
28662306a36Sopenharmony_ciMODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>");
28762306a36Sopenharmony_ciMODULE_DESCRIPTION("remote processor messaging tty driver");
28862306a36Sopenharmony_ciMODULE_LICENSE("GPL v2");
289