drivers/tty/rpmsg_tty.c

   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 <[email protected]>");
 287 MODULE_DESCRIPTION("remote processor messaging tty driver");
 288 MODULE_LICENSE("GPL v2");