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 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");