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 24 static DEFINE_IDR(tty_idr); /* tty instance id */ 25 static DEFINE_MUTEX(idr_lock); /* protects tty_idr */ 26 27 static struct tty_driver *rpmsg_tty_driver; 28 29 struct 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 35 static 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 50 static 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 61 static void rpmsg_tty_cleanup(struct tty_struct *tty) 62 { 63 tty_port_put(tty->port); 64 } 65 66 static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp) 67 { 68 return tty_port_open(tty->port, tty, filp); 69 } 70 71 static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp) 72 { 73 return tty_port_close(tty->port, tty, filp); 74 } 75 76 static 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 } 104 105 static 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 } 116 117 static void rpmsg_tty_hangup(struct tty_struct *tty) 118 { 119 tty_port_hangup(tty->port); 120 } 121 122 static 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 }; 131 132 static 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 } 154 155 static 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 } 165 166 static const struct tty_port_operations rpmsg_tty_port_ops = { 167 .destruct = rpmsg_tty_destruct_port, 168 }; 169 170 171 static 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 } 202 203 static 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 } 216 217 static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = { 218 { .name = "rpmsg-tty" }, 219 { }, 220 }; 221 MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table); 222 223 static 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 }; 230 231 static 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; 265 266 error_unregister: 267 tty_unregister_driver(rpmsg_tty_driver); 268 269 error_put: 270 tty_driver_kref_put(rpmsg_tty_driver); 271 272 return ret; 273 } 274 275 static 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 } 282 283 module_init(rpmsg_tty_init); 284 module_exit(rpmsg_tty_exit); 285 286 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>"); 287 MODULE_DESCRIPTION("remote processor messaging tty driver"); 288 MODULE_LICENSE("GPL v2"); 289