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
  54         tty->driver_data = cport;
  55
  56         return tty_port_install(&cport->port, driver, tty);
  57 }
  58
  59 static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
  60 {
  61         return tty_port_open(tty->port, tty, filp);
  62 }
  63
  64 static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
  65 {
  66         return tty_port_close(tty->port, tty, filp);
  67 }
  68
  69 static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
  70 {
  71         struct rpmsg_tty_port *cport = tty->driver_data;
  72         struct rpmsg_device *rpdev;
  73         int msg_max_size, msg_size;
  74         int ret;
  75
  76         rpdev = cport->rpdev;
  77
  78         msg_max_size = rpmsg_get_mtu(rpdev->ept);
  79         if (msg_max_size < 0)
  80                 return msg_max_size;
  81
  82         msg_size = min(len, msg_max_size);
  83
  84         /*
  85          * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
  86          * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
  87          */
  88         ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
  89         if (ret) {
  90                 dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
  91                 return ret;
  92         }
  93
  94         return msg_size;
  95 }
  96
  97 static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
  98 {
  99         struct rpmsg_tty_port *cport = tty->driver_data;
 100         int size;
 101
 102         size = rpmsg_get_mtu(cport->rpdev->ept);
 103         if (size < 0)
 104                 return 0;
 105
 106         return size;
 107 }
 108
 109 static const struct tty_operations rpmsg_tty_ops = {
 110         .install        = rpmsg_tty_install,
 111         .open           = rpmsg_tty_open,
 112         .close          = rpmsg_tty_close,
 113         .write          = rpmsg_tty_write,
 114         .write_room     = rpmsg_tty_write_room,
 115 };
 116
 117 static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
 118 {
 119         struct rpmsg_tty_port *cport;
 120         int ret;
 121
 122         cport = kzalloc(sizeof(*cport), GFP_KERNEL);
 123         if (!cport)
 124                 return ERR_PTR(-ENOMEM);
 125
 126         mutex_lock(&idr_lock);
 127         ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
 128         mutex_unlock(&idr_lock);
 129
 130         if (ret < 0) {
 131                 kfree(cport);
 132                 return ERR_PTR(ret);
 133         }
 134
 135         cport->id = ret;
 136
 137         return cport;
 138 }
 139
 140 static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport)
 141 {
 142         mutex_lock(&idr_lock);
 143         idr_remove(&tty_idr, cport->id);
 144         mutex_unlock(&idr_lock);
 145
 146         kfree(cport);
 147 }
 148
 149 static const struct tty_port_operations rpmsg_tty_port_ops = { };
 150
 151 static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
 152 {
 153         struct rpmsg_tty_port *cport;
 154         struct device *dev = &rpdev->dev;
 155         struct device *tty_dev;
 156         int ret;
 157
 158         cport = rpmsg_tty_alloc_cport();
 159         if (IS_ERR(cport))
 160                 return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
 161
 162         tty_port_init(&cport->port);
 163         cport->port.ops = &rpmsg_tty_port_ops;
 164
 165         tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
 166                                            cport->id, dev);
 167         if (IS_ERR(tty_dev)) {
 168                 ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
 169                 goto err_destroy;
 170         }
 171
 172         cport->rpdev = rpdev;
 173
 174         dev_set_drvdata(dev, cport);
 175
 176         dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
 177                 rpdev->src, rpdev->dst, cport->id);
 178
 179         return 0;
 180
 181 err_destroy:
 182         tty_port_destroy(&cport->port);
 183         rpmsg_tty_release_cport(cport);
 184
 185         return ret;
 186 }
 187
 188 static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
 189 {
 190         struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
 191
 192         dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
 193
 194         /* User hang up to release the tty */
 195         if (tty_port_initialized(&cport->port))
 196                 tty_port_tty_hangup(&cport->port, false);
 197
 198         tty_unregister_device(rpmsg_tty_driver, cport->id);
 199
 200         tty_port_destroy(&cport->port);
 201         rpmsg_tty_release_cport(cport);
 202 }
 203
 204 static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
 205         { .name = "rpmsg-tty" },
 206         { },
 207 };
 208 MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
 209
 210 static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
 211         .drv.name       = KBUILD_MODNAME,
 212         .id_table       = rpmsg_driver_tty_id_table,
 213         .probe          = rpmsg_tty_probe,
 214         .callback       = rpmsg_tty_cb,
 215         .remove         = rpmsg_tty_remove,
 216 };
 217
 218 static int __init rpmsg_tty_init(void)
 219 {
 220         int ret;
 221
 222         rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
 223                                             TTY_DRIVER_DYNAMIC_DEV);
 224         if (IS_ERR(rpmsg_tty_driver))
 225                 return PTR_ERR(rpmsg_tty_driver);
 226
 227         rpmsg_tty_driver->driver_name = "rpmsg_tty";
 228         rpmsg_tty_driver->name = RPMSG_TTY_NAME;
 229         rpmsg_tty_driver->major = 0;
 230         rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
 231
 232         /* Disable unused mode by default */
 233         rpmsg_tty_driver->init_termios = tty_std_termios;
 234         rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
 235         rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
 236
 237         tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
 238
 239         ret = tty_register_driver(rpmsg_tty_driver);
 240         if (ret < 0) {
 241                 pr_err("Couldn't install driver: %d\n", ret);
 242                 goto error_put;
 243         }
 244
 245         ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
 246         if (ret < 0) {
 247                 pr_err("Couldn't register driver: %d\n", ret);
 248                 goto error_unregister;
 249         }
 250
 251         return 0;
 252
 253 error_unregister:
 254         tty_unregister_driver(rpmsg_tty_driver);
 255
 256 error_put:
 257         tty_driver_kref_put(rpmsg_tty_driver);
 258
 259         return ret;
 260 }
 261
 262 static void __exit rpmsg_tty_exit(void)
 263 {
 264         unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
 265         tty_unregister_driver(rpmsg_tty_driver);
 266         tty_driver_kref_put(rpmsg_tty_driver);
 267         idr_destroy(&tty_idr);
 268 }
 269
 270 module_init(rpmsg_tty_init);
 271 module_exit(rpmsg_tty_exit);
 272
 273 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>");
 274 MODULE_DESCRIPTION("remote processor messaging tty driver");
 275 MODULE_LICENSE("GPL v2");