// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2021 STMicroelectronics - All Rights Reserved
*
* The rpmsg tty driver implements serial communication on the RPMsg bus to makes
* possible for user-space programs to send and receive rpmsg messages as a standard
* tty protocol.
*
* The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
* The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/rpmsg.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#define RPMSG_TTY_NAME "ttyRPMSG"
#define MAX_TTY_RPMSG 32
static DEFINE_IDR(tty_idr); /* tty instance id */
static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
static struct tty_driver *rpmsg_tty_driver;
struct rpmsg_tty_port {
struct tty_port port; /* TTY port data */
int id; /* TTY rpmsg index */
struct rpmsg_device *rpdev; /* rpmsg device */
};
static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
{
struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
int copied;
if (!len)
return -EINVAL;
copied = tty_insert_flip_string(&cport->port, data, len);
if (copied != len)
dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
tty_flip_buffer_push(&cport->port);
return 0;
}
static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
{
struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
struct tty_port *port;
tty->driver_data = cport;
port = tty_port_get(&cport->port);
return tty_port_install(port, driver, tty);
}
static void rpmsg_tty_cleanup(struct tty_struct *tty)
{
tty_port_put(tty->port);
}
static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
{
return tty_port_open(tty->port, tty, filp);
}
static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
{
return tty_port_close(tty->port, tty, filp);
}
static ssize_t rpmsg_tty_write(struct tty_struct *tty, const u8 *buf,
size_t len)
{
struct rpmsg_tty_port *cport = tty->driver_data;
struct rpmsg_device *rpdev;
int msg_max_size, msg_size;
int ret;
rpdev = cport->rpdev;
msg_max_size = rpmsg_get_mtu(rpdev->ept);
if (msg_max_size < 0)
return msg_max_size;
msg_size = min_t(unsigned int, len, msg_max_size);
/*
* Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
* hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
*/
ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
if (ret) {
dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
return ret;
}
return msg_size;
}
static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
{
struct rpmsg_tty_port *cport = tty->driver_data;
int size;
size = rpmsg_get_mtu(cport->rpdev->ept);
if (size < 0)
return 0;
return size;
}
static void rpmsg_tty_hangup(struct tty_struct *tty)
{
tty_port_hangup(tty->port);
}
static const struct tty_operations rpmsg_tty_ops = {
.install = rpmsg_tty_install,
.open = rpmsg_tty_open,
.close = rpmsg_tty_close,
.write = rpmsg_tty_write,
.write_room = rpmsg_tty_write_room,
.hangup = rpmsg_tty_hangup,
.cleanup = rpmsg_tty_cleanup,
};
static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
{
struct rpmsg_tty_port *cport;
int ret;
cport = kzalloc(sizeof(*cport), GFP_KERNEL);
if (!cport)
return ERR_PTR(-ENOMEM);
mutex_lock(&idr_lock);
ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
mutex_unlock(&idr_lock);
if (ret < 0) {
kfree(cport);
return ERR_PTR(ret);
}
cport->id = ret;
return cport;
}
static void rpmsg_tty_destruct_port(struct tty_port *port)
{
struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port);
mutex_lock(&idr_lock);
idr_remove(&tty_idr, cport->id);
mutex_unlock(&idr_lock);
kfree(cport);
}
static const struct tty_port_operations rpmsg_tty_port_ops = {
.destruct = rpmsg_tty_destruct_port,
};
static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
{
struct rpmsg_tty_port *cport;
struct device *dev = &rpdev->dev;
struct device *tty_dev;
int ret;
cport = rpmsg_tty_alloc_cport();
if (IS_ERR(cport))
return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
tty_port_init(&cport->port);
cport->port.ops = &rpmsg_tty_port_ops;
tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
cport->id, dev);
if (IS_ERR(tty_dev)) {
ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
tty_port_put(&cport->port);
return ret;
}
cport->rpdev = rpdev;
dev_set_drvdata(dev, cport);
dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
rpdev->src, rpdev->dst, cport->id);
return 0;
}
static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
{
struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
/* User hang up to release the tty */
tty_port_tty_hangup(&cport->port, false);
tty_unregister_device(rpmsg_tty_driver, cport->id);
tty_port_put(&cport->port);
}
static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
{ .name = "rpmsg-tty" },
{ },
};
MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
.drv.name = KBUILD_MODNAME,
.id_table = rpmsg_driver_tty_id_table,
.probe = rpmsg_tty_probe,
.callback = rpmsg_tty_cb,
.remove = rpmsg_tty_remove,
};
static int __init rpmsg_tty_init(void)
{
int ret;
rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
TTY_DRIVER_DYNAMIC_DEV);
if (IS_ERR(rpmsg_tty_driver))
return PTR_ERR(rpmsg_tty_driver);
rpmsg_tty_driver->driver_name = "rpmsg_tty";
rpmsg_tty_driver->name = RPMSG_TTY_NAME;
rpmsg_tty_driver->major = 0;
rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
/* Disable unused mode by default */
rpmsg_tty_driver->init_termios = tty_std_termios;
rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
ret = tty_register_driver(rpmsg_tty_driver);
if (ret < 0) {
pr_err("Couldn't install driver: %d\n", ret);
goto error_put;
}
ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
if (ret < 0) {
pr_err("Couldn't register driver: %d\n", ret);
goto error_unregister;
}
return 0;
error_unregister:
tty_unregister_driver(rpmsg_tty_driver);
error_put:
tty_driver_kref_put(rpmsg_tty_driver);
return ret;
}
static void __exit rpmsg_tty_exit(void)
{
unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
tty_unregister_driver(rpmsg_tty_driver);
tty_driver_kref_put(rpmsg_tty_driver);
idr_destroy(&tty_idr);
}
module_init(rpmsg_tty_init);
module_exit(rpmsg_tty_exit);
MODULE_AUTHOR("Arnaud Pouliquen <[email protected]>");
MODULE_DESCRIPTION("remote processor messaging tty driver");
MODULE_LICENSE("GPL v2");
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