drivers/tty/rpmsg_tty.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Copyright (C) 2021 STMicroelectronics - All Rights Reserved
0004  *
0005  * The rpmsg tty driver implements serial communication on the RPMsg bus to makes
0006  * possible for user-space programs to send and receive rpmsg messages as a standard
0007  * tty protocol.
0008  *
0009  * The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
0010  * The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
0011  */
0012
0013 #define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
0014
0015 #include <linux/module.h>
0016 #include <linux/rpmsg.h>
0017 #include <linux/slab.h>
0018 #include <linux/tty.h>
0019 #include <linux/tty_flip.h>
0020
0021 #define RPMSG_TTY_NAME  "ttyRPMSG"
0022 #define MAX_TTY_RPMSG   32
0023
0024 static DEFINE_IDR(tty_idr); /* tty instance id */
0025 static DEFINE_MUTEX(idr_lock);  /* protects tty_idr */
0026
0027 static struct tty_driver *rpmsg_tty_driver;
0028
0029 struct rpmsg_tty_port {
0030     struct tty_port     port;    /* TTY port data */
0031     int         id;  /* TTY rpmsg index */
0032     struct rpmsg_device *rpdev;  /* rpmsg device */
0033 };
0034
0035 static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
0036 {
0037     struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
0038     int copied;
0039
0040     if (!len)
0041         return -EINVAL;
0042     copied = tty_insert_flip_string(&cport->port, data, len);
0043     if (copied != len)
0044         dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
0045     tty_flip_buffer_push(&cport->port);
0046
0047     return 0;
0048 }
0049
0050 static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
0051 {
0052     struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
0053     struct tty_port *port;
0054
0055     tty->driver_data = cport;
0056
0057     port = tty_port_get(&cport->port);
0058     return tty_port_install(port, driver, tty);
0059 }
0060
0061 static void rpmsg_tty_cleanup(struct tty_struct *tty)
0062 {
0063     tty_port_put(tty->port);
0064 }
0065
0066 static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
0067 {
0068     return tty_port_open(tty->port, tty, filp);
0069 }
0070
0071 static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
0072 {
0073     return tty_port_close(tty->port, tty, filp);
0074 }
0075
0076 static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
0077 {
0078     struct rpmsg_tty_port *cport = tty->driver_data;
0079     struct rpmsg_device *rpdev;
0080     int msg_max_size, msg_size;
0081     int ret;
0082
0083     rpdev = cport->rpdev;
0084
0085     msg_max_size = rpmsg_get_mtu(rpdev->ept);
0086     if (msg_max_size < 0)
0087         return msg_max_size;
0088
0089     msg_size = min(len, msg_max_size);
0090
0091     /*
0092      * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
0093      * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
0094      */
0095     ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
0096     if (ret) {
0097         dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
0098         return ret;
0099     }
0100
0101     return msg_size;
0102 }
0103
0104 static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
0105 {
0106     struct rpmsg_tty_port *cport = tty->driver_data;
0107     int size;
0108
0109     size = rpmsg_get_mtu(cport->rpdev->ept);
0110     if (size < 0)
0111         return 0;
0112
0113     return size;
0114 }
0115
0116 static void rpmsg_tty_hangup(struct tty_struct *tty)
0117 {
0118     tty_port_hangup(tty->port);
0119 }
0120
0121 static const struct tty_operations rpmsg_tty_ops = {
0122     .install    = rpmsg_tty_install,
0123     .open       = rpmsg_tty_open,
0124     .close      = rpmsg_tty_close,
0125     .write      = rpmsg_tty_write,
0126     .write_room = rpmsg_tty_write_room,
0127     .hangup     = rpmsg_tty_hangup,
0128     .cleanup    = rpmsg_tty_cleanup,
0129 };
0130
0131 static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
0132 {
0133     struct rpmsg_tty_port *cport;
0134     int ret;
0135
0136     cport = kzalloc(sizeof(*cport), GFP_KERNEL);
0137     if (!cport)
0138         return ERR_PTR(-ENOMEM);
0139
0140     mutex_lock(&idr_lock);
0141     ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
0142     mutex_unlock(&idr_lock);
0143
0144     if (ret < 0) {
0145         kfree(cport);
0146         return ERR_PTR(ret);
0147     }
0148
0149     cport->id = ret;
0150
0151     return cport;
0152 }
0153
0154 static void rpmsg_tty_destruct_port(struct tty_port *port)
0155 {
0156     struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port);
0157
0158     mutex_lock(&idr_lock);
0159     idr_remove(&tty_idr, cport->id);
0160     mutex_unlock(&idr_lock);
0161
0162     kfree(cport);
0163 }
0164
0165 static const struct tty_port_operations rpmsg_tty_port_ops = {
0166     .destruct = rpmsg_tty_destruct_port,
0167 };
0168
0169
0170 static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
0171 {
0172     struct rpmsg_tty_port *cport;
0173     struct device *dev = &rpdev->dev;
0174     struct device *tty_dev;
0175     int ret;
0176
0177     cport = rpmsg_tty_alloc_cport();
0178     if (IS_ERR(cport))
0179         return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
0180
0181     tty_port_init(&cport->port);
0182     cport->port.ops = &rpmsg_tty_port_ops;
0183
0184     tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
0185                        cport->id, dev);
0186     if (IS_ERR(tty_dev)) {
0187         ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
0188         tty_port_put(&cport->port);
0189         return ret;
0190     }
0191
0192     cport->rpdev = rpdev;
0193
0194     dev_set_drvdata(dev, cport);
0195
0196     dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
0197         rpdev->src, rpdev->dst, cport->id);
0198
0199     return 0;
0200 }
0201
0202 static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
0203 {
0204     struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
0205
0206     dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
0207
0208     /* User hang up to release the tty */
0209     tty_port_tty_hangup(&cport->port, false);
0210
0211     tty_unregister_device(rpmsg_tty_driver, cport->id);
0212
0213     tty_port_put(&cport->port);
0214 }
0215
0216 static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
0217     { .name = "rpmsg-tty" },
0218     { },
0219 };
0220 MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
0221
0222 static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
0223     .drv.name   = KBUILD_MODNAME,
0224     .id_table   = rpmsg_driver_tty_id_table,
0225     .probe      = rpmsg_tty_probe,
0226     .callback   = rpmsg_tty_cb,
0227     .remove     = rpmsg_tty_remove,
0228 };
0229
0230 static int __init rpmsg_tty_init(void)
0231 {
0232     int ret;
0233
0234     rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
0235                         TTY_DRIVER_DYNAMIC_DEV);
0236     if (IS_ERR(rpmsg_tty_driver))
0237         return PTR_ERR(rpmsg_tty_driver);
0238
0239     rpmsg_tty_driver->driver_name = "rpmsg_tty";
0240     rpmsg_tty_driver->name = RPMSG_TTY_NAME;
0241     rpmsg_tty_driver->major = 0;
0242     rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
0243
0244     /* Disable unused mode by default */
0245     rpmsg_tty_driver->init_termios = tty_std_termios;
0246     rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
0247     rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
0248
0249     tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
0250
0251     ret = tty_register_driver(rpmsg_tty_driver);
0252     if (ret < 0) {
0253         pr_err("Couldn't install driver: %d\n", ret);
0254         goto error_put;
0255     }
0256
0257     ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
0258     if (ret < 0) {
0259         pr_err("Couldn't register driver: %d\n", ret);
0260         goto error_unregister;
0261     }
0262
0263     return 0;
0264
0265 error_unregister:
0266     tty_unregister_driver(rpmsg_tty_driver);
0267
0268 error_put:
0269     tty_driver_kref_put(rpmsg_tty_driver);
0270
0271     return ret;
0272 }
0273
0274 static void __exit rpmsg_tty_exit(void)
0275 {
0276     unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
0277     tty_unregister_driver(rpmsg_tty_driver);
0278     tty_driver_kref_put(rpmsg_tty_driver);
0279     idr_destroy(&tty_idr);
0280 }
0281
0282 module_init(rpmsg_tty_init);
0283 module_exit(rpmsg_tty_exit);
0284
0285 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>");
0286 MODULE_DESCRIPTION("remote processor messaging tty driver");
0287 MODULE_LICENSE("GPL v2");