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 int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len) 77 { 78 struct rpmsg_tty_port *cport = tty->driver_data; 79 struct rpmsg_device *rpdev; 80 int msg_max_size, msg_size; 81 int ret; 82 83 rpdev = cport->rpdev; 84 85 msg_max_size = rpmsg_get_mtu(rpdev->ept); 86 if (msg_max_size < 0) 87 return msg_max_size; 88 89 msg_size = min(len, msg_max_size); 90 91 /* 92 * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not 93 * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM. 94 */ 95 ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size); 96 if (ret) { 97 dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret); 98 return ret; 99 } 100 101 return msg_size; 102 } 103 104 static unsigned int rpmsg_tty_write_room(struct tty_struct *tty) 105 { 106 struct rpmsg_tty_port *cport = tty->driver_data; 107 int size; 108 109 size = rpmsg_get_mtu(cport->rpdev->ept); 110 if (size < 0) 111 return 0; 112 113 return size; 114 } 115 116 static void rpmsg_tty_hangup(struct tty_struct *tty) 117 { 118 tty_port_hangup(tty->port); 119 } 120 121 static const struct tty_operations rpmsg_tty_ops = { 122 .install = rpmsg_tty_install, 123 .open = rpmsg_tty_open, 124 .close = rpmsg_tty_close, 125 .write = rpmsg_tty_write, 126 .write_room = rpmsg_tty_write_room, 127 .hangup = rpmsg_tty_hangup, 128 .cleanup = rpmsg_tty_cleanup, 129 }; 130 131 static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void) 132 { 133 struct rpmsg_tty_port *cport; 134 int ret; 135 136 cport = kzalloc(sizeof(*cport), GFP_KERNEL); 137 if (!cport) 138 return ERR_PTR(-ENOMEM); 139 140 mutex_lock(&idr_lock); 141 ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL); 142 mutex_unlock(&idr_lock); 143 144 if (ret < 0) { 145 kfree(cport); 146 return ERR_PTR(ret); 147 } 148 149 cport->id = ret; 150 151 return cport; 152 } 153 154 static void rpmsg_tty_destruct_port(struct tty_port *port) 155 { 156 struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port); 157 158 mutex_lock(&idr_lock); 159 idr_remove(&tty_idr, cport->id); 160 mutex_unlock(&idr_lock); 161 162 kfree(cport); 163 } 164 165 static const struct tty_port_operations rpmsg_tty_port_ops = { 166 .destruct = rpmsg_tty_destruct_port, 167 }; 168 169 170 static int rpmsg_tty_probe(struct rpmsg_device *rpdev) 171 { 172 struct rpmsg_tty_port *cport; 173 struct device *dev = &rpdev->dev; 174 struct device *tty_dev; 175 int ret; 176 177 cport = rpmsg_tty_alloc_cport(); 178 if (IS_ERR(cport)) 179 return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n"); 180 181 tty_port_init(&cport->port); 182 cport->port.ops = &rpmsg_tty_port_ops; 183 184 tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver, 185 cport->id, dev); 186 if (IS_ERR(tty_dev)) { 187 ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n"); 188 tty_port_put(&cport->port); 189 return ret; 190 } 191 192 cport->rpdev = rpdev; 193 194 dev_set_drvdata(dev, cport); 195 196 dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n", 197 rpdev->src, rpdev->dst, cport->id); 198 199 return 0; 200 } 201 202 static void rpmsg_tty_remove(struct rpmsg_device *rpdev) 203 { 204 struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev); 205 206 dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id); 207 208 /* User hang up to release the tty */ 209 tty_port_tty_hangup(&cport->port, false); 210 211 tty_unregister_device(rpmsg_tty_driver, cport->id); 212 213 tty_port_put(&cport->port); 214 } 215 216 static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = { 217 { .name = "rpmsg-tty" }, 218 { }, 219 }; 220 MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table); 221 222 static struct rpmsg_driver rpmsg_tty_rpmsg_drv = { 223 .drv.name = KBUILD_MODNAME, 224 .id_table = rpmsg_driver_tty_id_table, 225 .probe = rpmsg_tty_probe, 226 .callback = rpmsg_tty_cb, 227 .remove = rpmsg_tty_remove, 228 }; 229 230 static int __init rpmsg_tty_init(void) 231 { 232 int ret; 233 234 rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW | 235 TTY_DRIVER_DYNAMIC_DEV); 236 if (IS_ERR(rpmsg_tty_driver)) 237 return PTR_ERR(rpmsg_tty_driver); 238 239 rpmsg_tty_driver->driver_name = "rpmsg_tty"; 240 rpmsg_tty_driver->name = RPMSG_TTY_NAME; 241 rpmsg_tty_driver->major = 0; 242 rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE; 243 244 /* Disable unused mode by default */ 245 rpmsg_tty_driver->init_termios = tty_std_termios; 246 rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON); 247 rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR); 248 249 tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops); 250 251 ret = tty_register_driver(rpmsg_tty_driver); 252 if (ret < 0) { 253 pr_err("Couldn't install driver: %d\n", ret); 254 goto error_put; 255 } 256 257 ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv); 258 if (ret < 0) { 259 pr_err("Couldn't register driver: %d\n", ret); 260 goto error_unregister; 261 } 262 263 return 0; 264 265 error_unregister: 266 tty_unregister_driver(rpmsg_tty_driver); 267 268 error_put: 269 tty_driver_kref_put(rpmsg_tty_driver); 270 271 return ret; 272 } 273 274 static void __exit rpmsg_tty_exit(void) 275 { 276 unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv); 277 tty_unregister_driver(rpmsg_tty_driver); 278 tty_driver_kref_put(rpmsg_tty_driver); 279 idr_destroy(&tty_idr); 280 } 281 282 module_init(rpmsg_tty_init); 283 module_exit(rpmsg_tty_exit); 284 285 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>"); 286 MODULE_DESCRIPTION("remote processor messaging tty driver"); 287 MODULE_LICENSE("GPL v2"); 288