rpmsg_tty.c 6.9 KB

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  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. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13. #include <linux/module.h>
  14. #include <linux/rpmsg.h>
  15. #include <linux/slab.h>
  16. #include <linux/tty.h>
  17. #include <linux/tty_flip.h>
  18. #define RPMSG_TTY_NAME "ttyRPMSG"
  19. #define MAX_TTY_RPMSG 32
  20. static DEFINE_IDR(tty_idr); /* tty instance id */
  21. static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
  22. static struct tty_driver *rpmsg_tty_driver;
  23. struct rpmsg_tty_port {
  24. struct tty_port port; /* TTY port data */
  25. int id; /* TTY rpmsg index */
  26. struct rpmsg_device *rpdev; /* rpmsg device */
  27. };
  28. static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
  29. {
  30. struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
  31. int copied;
  32. if (!len)
  33. return -EINVAL;
  34. copied = tty_insert_flip_string(&cport->port, data, len);
  35. if (copied != len)
  36. dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
  37. tty_flip_buffer_push(&cport->port);
  38. return 0;
  39. }
  40. static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
  41. {
  42. struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
  43. struct tty_port *port;
  44. tty->driver_data = cport;
  45. port = tty_port_get(&cport->port);
  46. return tty_port_install(port, driver, tty);
  47. }
  48. static void rpmsg_tty_cleanup(struct tty_struct *tty)
  49. {
  50. tty_port_put(tty->port);
  51. }
  52. static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
  53. {
  54. return tty_port_open(tty->port, tty, filp);
  55. }
  56. static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
  57. {
  58. return tty_port_close(tty->port, tty, filp);
  59. }
  60. static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
  61. {
  62. struct rpmsg_tty_port *cport = tty->driver_data;
  63. struct rpmsg_device *rpdev;
  64. int msg_max_size, msg_size;
  65. int ret;
  66. rpdev = cport->rpdev;
  67. msg_max_size = rpmsg_get_mtu(rpdev->ept);
  68. if (msg_max_size < 0)
  69. return msg_max_size;
  70. msg_size = min(len, msg_max_size);
  71. /*
  72. * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
  73. * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
  74. */
  75. ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
  76. if (ret) {
  77. dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
  78. return ret;
  79. }
  80. return msg_size;
  81. }
  82. static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
  83. {
  84. struct rpmsg_tty_port *cport = tty->driver_data;
  85. int size;
  86. size = rpmsg_get_mtu(cport->rpdev->ept);
  87. if (size < 0)
  88. return 0;
  89. return size;
  90. }
  91. static void rpmsg_tty_hangup(struct tty_struct *tty)
  92. {
  93. tty_port_hangup(tty->port);
  94. }
  95. static const struct tty_operations rpmsg_tty_ops = {
  96. .install = rpmsg_tty_install,
  97. .open = rpmsg_tty_open,
  98. .close = rpmsg_tty_close,
  99. .write = rpmsg_tty_write,
  100. .write_room = rpmsg_tty_write_room,
  101. .hangup = rpmsg_tty_hangup,
  102. .cleanup = rpmsg_tty_cleanup,
  103. };
  104. static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
  105. {
  106. struct rpmsg_tty_port *cport;
  107. int ret;
  108. cport = kzalloc(sizeof(*cport), GFP_KERNEL);
  109. if (!cport)
  110. return ERR_PTR(-ENOMEM);
  111. mutex_lock(&idr_lock);
  112. ret = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
  113. mutex_unlock(&idr_lock);
  114. if (ret < 0) {
  115. kfree(cport);
  116. return ERR_PTR(ret);
  117. }
  118. cport->id = ret;
  119. return cport;
  120. }
  121. static void rpmsg_tty_destruct_port(struct tty_port *port)
  122. {
  123. struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port);
  124. mutex_lock(&idr_lock);
  125. idr_remove(&tty_idr, cport->id);
  126. mutex_unlock(&idr_lock);
  127. kfree(cport);
  128. }
  129. static const struct tty_port_operations rpmsg_tty_port_ops = {
  130. .destruct = rpmsg_tty_destruct_port,
  131. };
  132. static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
  133. {
  134. struct rpmsg_tty_port *cport;
  135. struct device *dev = &rpdev->dev;
  136. struct device *tty_dev;
  137. int ret;
  138. cport = rpmsg_tty_alloc_cport();
  139. if (IS_ERR(cport))
  140. return dev_err_probe(dev, PTR_ERR(cport), "Failed to alloc tty port\n");
  141. tty_port_init(&cport->port);
  142. cport->port.ops = &rpmsg_tty_port_ops;
  143. tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
  144. cport->id, dev);
  145. if (IS_ERR(tty_dev)) {
  146. ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n");
  147. tty_port_put(&cport->port);
  148. return ret;
  149. }
  150. cport->rpdev = rpdev;
  151. dev_set_drvdata(dev, cport);
  152. dev_dbg(dev, "New channel: 0x%x -> 0x%x: " RPMSG_TTY_NAME "%d\n",
  153. rpdev->src, rpdev->dst, cport->id);
  154. return 0;
  155. }
  156. static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
  157. {
  158. struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
  159. dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
  160. /* User hang up to release the tty */
  161. tty_port_tty_hangup(&cport->port, false);
  162. tty_unregister_device(rpmsg_tty_driver, cport->id);
  163. tty_port_put(&cport->port);
  164. }
  165. static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
  166. { .name = "rpmsg-tty" },
  167. { },
  168. };
  169. MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
  170. static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
  171. .drv.name = KBUILD_MODNAME,
  172. .id_table = rpmsg_driver_tty_id_table,
  173. .probe = rpmsg_tty_probe,
  174. .callback = rpmsg_tty_cb,
  175. .remove = rpmsg_tty_remove,
  176. };
  177. static int __init rpmsg_tty_init(void)
  178. {
  179. int ret;
  180. rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
  181. TTY_DRIVER_DYNAMIC_DEV);
  182. if (IS_ERR(rpmsg_tty_driver))
  183. return PTR_ERR(rpmsg_tty_driver);
  184. rpmsg_tty_driver->driver_name = "rpmsg_tty";
  185. rpmsg_tty_driver->name = RPMSG_TTY_NAME;
  186. rpmsg_tty_driver->major = 0;
  187. rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
  188. /* Disable unused mode by default */
  189. rpmsg_tty_driver->init_termios = tty_std_termios;
  190. rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
  191. rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
  192. tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
  193. ret = tty_register_driver(rpmsg_tty_driver);
  194. if (ret < 0) {
  195. pr_err("Couldn't install driver: %d\n", ret);
  196. goto error_put;
  197. }
  198. ret = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
  199. if (ret < 0) {
  200. pr_err("Couldn't register driver: %d\n", ret);
  201. goto error_unregister;
  202. }
  203. return 0;
  204. error_unregister:
  205. tty_unregister_driver(rpmsg_tty_driver);
  206. error_put:
  207. tty_driver_kref_put(rpmsg_tty_driver);
  208. return ret;
  209. }
  210. static void __exit rpmsg_tty_exit(void)
  211. {
  212. unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
  213. tty_unregister_driver(rpmsg_tty_driver);
  214. tty_driver_kref_put(rpmsg_tty_driver);
  215. idr_destroy(&tty_idr);
  216. }
  217. module_init(rpmsg_tty_init);
  218. module_exit(rpmsg_tty_exit);
  219. MODULE_AUTHOR("Arnaud Pouliquen <[email protected]>");
  220. MODULE_DESCRIPTION("remote processor messaging tty driver");
  221. MODULE_LICENSE("GPL v2");