This driver exposes a standard TTY interface on top of the rpmsg
framework through a rpmsg service.
This driver supports multi-instances, offering a /dev/ttyRPMSGx entry
per rpmsg endpoint.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
---
Documentation/serial/tty_rpmsg.rst | 45 ++++
drivers/tty/Kconfig | 9 +
drivers/tty/Makefile | 1 +
drivers/tty/rpmsg_tty.c | 417 +++++++++++++++++++++++++++++
4 files changed, 472 insertions(+)
create mode 100644 Documentation/serial/tty_rpmsg.rst
create mode 100644 drivers/tty/rpmsg_tty.c
diff --git a/Documentation/serial/tty_rpmsg.rst b/Documentation/serial/tty_rpmsg.rst
new file mode 100644
index 000000000000..fc1d3fba73c5
--- /dev/null
+++ b/Documentation/serial/tty_rpmsg.rst
@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+The rpmsg TTY
+=============
+
+The rpmsg tty driver implements serial communication on the RPMsg bus to makes possible for user-space programs to send and receive rpmsg messages as a standard tty protocol.
+
+The remote processor can instantiate a new tty by requesting:
+- a "rpmsg-tty-raw" RPMsg service, for TTY raw data support without flow control
+- a "rpmsg-tty-ctrl" RPMSg service, for TTY support with flow control.
+
+Information related to the RPMsg and associated tty device is available in
+/sys/bus/rpmsg/devices/.
+
+RPMsg TTY without control
+---------------------
+
+The default end point associated with the "rpmsg-tty-raw" service is directly
+used for data exchange. No flow control is available.
+
+To be compliant with this driver, the remote firmware must create its data end point associated with the "rpmsg-tty-raw" service.
+
+RPMsg TTY with control
+---------------------
+
+The default end point associated with the "rpmsg-tty-ctrl" service is reserved for
+the control. A second endpoint must be created for data exchange.
+
+The control channel is used to transmit to the remote processor the CTS status,
+as well as the end point address for data transfer.
+
+To be compatible with this driver, the remote firmware must create or use its end point associated with "rpmsg-tty-ctrl" service, plus a second endpoint for the data flow.
+On Linux rpmsg_tty probes, the data endpoint address and the CTS (set to disable)
+is sent to the remote processor.
+The remote processor has to respect following rules:
+- It only transmits data when Linux remote cts is enable, otherwise message
+ could be lost.
+- It can pause/resume reception by sending a control message (rely on CTS state).
+
+Control message structure:
+struct rpmsg_tty_ctrl {
+ u8 cts; /* remote reception status */
+ u16 d_ept_addr; /* data endpoint address */
+};
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index a312cb33a99b..9d3ff6df9f25 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -454,6 +454,15 @@ config VCC
help
Support for Sun logical domain consoles.
+config RPMSG_TTY
+ tristate "RPMSG tty driver"
+ depends on RPMSG
+ help
+ Say y here to export rpmsg endpoints as tty devices, usually found
+ in /dev/ttyRPMSGx.
+ This makes it possible for user-space programs to send and receive
+ rpmsg messages as a standard tty protocol.
+
config LDISC_AUTOLOAD
bool "Automatically load TTY Line Disciplines"
default y
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 020b1cd9294f..c2465e7ebc2a 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -34,5 +34,6 @@ obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o
obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o
obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
obj-$(CONFIG_VCC) += vcc.o
+obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o
obj-y += ipwireless/
diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c
new file mode 100644
index 000000000000..49ce3b72781a
--- /dev/null
+++ b/drivers/tty/rpmsg_tty.c
@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
+ * Authors: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx> for STMicroelectronics.
+ */
+
+#include <linux/module.h>
+#include <linux/rpmsg.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#define MAX_TTY_RPMSG 32
+
+#define TTY_CH_NAME_RAW "rpmsg-tty-raw"
+#define TTY_CH_NAME_WITH_CTS "rpmsg-tty-ctrl"
+
+static DEFINE_IDR(tty_idr); /* tty instance id */
+static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
+
+static struct tty_driver *rpmsg_tty_driver;
+
+struct rpmsg_tty_ctrl {
+ u16 d_ept_addr; /* data endpoint address */
+ u8 cts; /* remote reception status */
+} __packed;
+
+struct rpmsg_tty_port {
+ struct tty_port port; /* TTY port data */
+ int id; /* TTY rpmsg index */
+ bool cts; /* remote reception status */
+ struct rpmsg_device *rpdev; /* rpmsg device */
+ struct rpmsg_endpoint *cs_ept; /* channel control endpoint */
+ struct rpmsg_endpoint *d_ept; /* data endpoint */
+ u32 data_dst; /* data destination endpoint address */
+};
+
+typedef void (*rpmsg_tty_rx_cb_t)(struct rpmsg_device *, void *, int, void *,
+ u32);
+
+static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
+ void *priv, u32 src)
+{
+ struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
+ int copied;
+
+ if (src == cport->data_dst) {
+ /* data message */
+ if (!len)
+ return -EINVAL;
+ copied = tty_insert_flip_string_fixed_flag(&cport->port, data,
+ TTY_NORMAL, len);
+ if (copied != len)
+ dev_dbg(&rpdev->dev, "trunc buffer: available space is %d\n",
+ copied);
+ tty_flip_buffer_push(&cport->port);
+ } else {
+ /* control message */
+ struct rpmsg_tty_ctrl *msg = data;
+
+ if (len != sizeof(*msg))
+ return -EINVAL;
+
+ cport->data_dst = msg->d_ept_addr;
+
+ /* Update remote cts state */
+ cport->cts = msg->cts ? 1 : 0;
+
+ if (cport->cts)
+ tty_port_tty_wakeup(&cport->port);
+ }
+
+ return 0;
+}
+
+static void rpmsg_tty_send_term_ready(struct tty_struct *tty, u8 state)
+{
+ struct rpmsg_tty_port *cport = tty->driver_data;
+ struct rpmsg_tty_ctrl m_ctrl;
+ int ret;
+
+ m_ctrl.cts = state;
+ m_ctrl.d_ept_addr = cport->d_ept->addr;
+
+ ret = rpmsg_trysend(cport->cs_ept, &m_ctrl, sizeof(m_ctrl));
+ if (ret < 0)
+ dev_dbg(tty->dev, "cannot send control (%d)\n", ret);
+};
+
+static void rpmsg_tty_throttle(struct tty_struct *tty)
+{
+ struct rpmsg_tty_port *cport = tty->driver_data;
+
+ /* Disable remote transmission */
+ if (cport->cs_ept)
+ rpmsg_tty_send_term_ready(tty, 0);
+};
+
+static void rpmsg_tty_unthrottle(struct tty_struct *tty)
+{
+ struct rpmsg_tty_port *cport = tty->driver_data;
+
+ /* Enable remote transmission */
+ if (cport->cs_ept)
+ rpmsg_tty_send_term_ready(tty, 1);
+};
+
+static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+ struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
+
+ if (!cport) {
+ dev_err(tty->dev, "cannot get cport\n");
+ return -ENODEV;
+ }
+
+ tty->driver_data = cport;
+
+ return tty_port_install(&cport->port, driver, tty);
+}
+
+static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
+{
+ return tty_port_open(tty->port, tty, filp);
+}
+
+static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
+{
+ return tty_port_close(tty->port, tty, filp);
+}
+
+static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
+{
+ struct rpmsg_tty_port *cport = tty->driver_data;
+ struct rpmsg_device *rpdev;
+ int msg_max_size, msg_size;
+ int ret;
+ u8 *tmpbuf;
+
+ /* If cts not set, the message is not sent*/
+ if (!cport->cts)
+ return 0;
+
+ rpdev = cport->rpdev;
+
+ dev_dbg(&rpdev->dev, "%s: send msg from tty->index = %d, len = %d\n",
+ __func__, tty->index, len);
+
+ msg_max_size = rpmsg_get_mtu(rpdev->ept);
+
+ msg_size = min(len, msg_max_size);
+ tmpbuf = kzalloc(msg_size, GFP_KERNEL);
+ if (!tmpbuf)
+ return -ENOMEM;
+
+ memcpy(tmpbuf, buf, msg_size);
+
+ /*
+ * Try to send the message to remote processor, if failed return 0 as
+ * no data sent
+ */
+ ret = rpmsg_trysendto(cport->d_ept, tmpbuf, msg_size, cport->data_dst);
+ kfree(tmpbuf);
+ if (ret) {
+ dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
+ return 0;
+ }
+
+ return msg_size;
+}
+
+static int rpmsg_tty_write_room(struct tty_struct *tty)
+{
+ struct rpmsg_tty_port *cport = tty->driver_data;
+
+ return cport->cts ? rpmsg_get_mtu(cport->rpdev->ept) : 0;
+}
+
+static const struct tty_operations rpmsg_tty_ops = {
+ .install = rpmsg_tty_install,
+ .open = rpmsg_tty_open,
+ .close = rpmsg_tty_close,
+ .write = rpmsg_tty_write,
+ .write_room = rpmsg_tty_write_room,
+ .throttle = rpmsg_tty_throttle,
+ .unthrottle = rpmsg_tty_unthrottle,
+};
+
+static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
+{
+ struct rpmsg_tty_port *cport;
+
+ cport = kzalloc(sizeof(*cport), GFP_KERNEL);
+ if (!cport)
+ return ERR_PTR(-ENOMEM);
+
+ mutex_lock(&idr_lock);
+ cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
+ mutex_unlock(&idr_lock);
+
+ if (cport->id < 0) {
+ kfree(cport);
+ return ERR_PTR(-ENOSPC);
+ }
+
+ return cport;
+}
+
+static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport)
+{
+ mutex_lock(&idr_lock);
+ idr_remove(&tty_idr, cport->id);
+ mutex_unlock(&idr_lock);
+
+ kfree(cport);
+}
+
+static int rpmsg_tty_port_activate(struct tty_port *p, struct tty_struct *tty)
+{
+ p->low_latency = (p->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
+
+ /* Allocate the buffer we use for writing data */
+ return tty_port_alloc_xmit_buf(p);
+}
+
+static void rpmsg_tty_port_shutdown(struct tty_port *p)
+{
+ /* Free the write buffer */
+ tty_port_free_xmit_buf(p);
+}
+
+static void rpmsg_tty_dtr_rts(struct tty_port *port, int raise)
+{
+ dev_dbg(port->tty->dev, "%s: dtr_rts state %d\n", __func__, raise);
+
+ if (raise)
+ rpmsg_tty_unthrottle(port->tty);
+ else
+ rpmsg_tty_throttle(port->tty);
+}
+
+static const struct tty_port_operations rpmsg_tty_port_ops = {
+ .activate = rpmsg_tty_port_activate,
+ .shutdown = rpmsg_tty_port_shutdown,
+ .dtr_rts = rpmsg_tty_dtr_rts,
+};
+
+static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
+{
+ struct rpmsg_tty_port *cport;
+ struct device *dev = &rpdev->dev;
+ struct rpmsg_channel_info chinfo;
+ struct device *tty_dev;
+ int ret;
+
+ cport = rpmsg_tty_alloc_cport();
+ if (IS_ERR(cport)) {
+ dev_err(dev, "failed to alloc tty port\n");
+ return PTR_ERR(cport);
+ }
+
+ if (!strncmp(rpdev->id.name, TTY_CH_NAME_WITH_CTS,
+ sizeof(TTY_CH_NAME_WITH_CTS))) {
+ /*
+ * the default endpoint is used for control. Create a second
+ * endpoint for the data that would be exchanges trough control
+ * endpoint. address of the data endpoint will be provided with
+ * the cts state
+ */
+ cport->cs_ept = rpdev->ept;
+ cport->data_dst = RPMSG_ADDR_ANY;
+
+ strscpy(chinfo.name, TTY_CH_NAME_WITH_CTS, sizeof(chinfo.name));
+ chinfo.src = RPMSG_ADDR_ANY;
+ chinfo.dst = RPMSG_ADDR_ANY;
+
+ cport->d_ept = rpmsg_create_ept(rpdev, rpmsg_tty_cb, cport,
+ chinfo);
+ if (!cport->d_ept) {
+ dev_err(dev, "failed to create tty control channel\n");
+ ret = -ENOMEM;
+ goto err_r_cport;
+ }
+ dev_dbg(dev, "%s: creating data endpoint with address %#x\n",
+ __func__, cport->d_ept->addr);
+ } else {
+ /*
+ * TTY over rpmsg without CTS management the default endpoint
+ * is use for raw data transmission.
+ */
+ cport->cs_ept = NULL;
+ cport->cts = 1;
+ cport->d_ept = rpdev->ept;
+ cport->data_dst = rpdev->dst;
+ }
+
+ tty_port_init(&cport->port);
+ cport->port.ops = &rpmsg_tty_port_ops;
+
+ tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
+ cport->id, dev);
+ if (IS_ERR(tty_dev)) {
+ dev_err(dev, "failed to register tty port\n");
+ ret = PTR_ERR(tty_dev);
+ goto err_destroy;
+ }
+
+ cport->rpdev = rpdev;
+
+ dev_set_drvdata(dev, cport);
+
+ dev_dbg(dev, "new channel: 0x%x -> 0x%x : ttyRPMSG%d\n",
+ rpdev->src, rpdev->dst, cport->id);
+
+ return 0;
+
+err_destroy:
+ tty_port_destroy(&cport->port);
+ if (cport->cs_ept)
+ rpmsg_destroy_ept(cport->d_ept);
+err_r_cport:
+ rpmsg_tty_release_cport(cport);
+
+ return ret;
+}
+
+static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
+{
+ struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
+
+ dev_dbg(&rpdev->dev, "removing rpmsg tty device %d\n", cport->id);
+
+ /* User hang up to release the tty */
+ if (tty_port_initialized(&cport->port))
+ tty_port_tty_hangup(&cport->port, false);
+
+ tty_unregister_device(rpmsg_tty_driver, cport->id);
+
+ tty_port_destroy(&cport->port);
+ if (cport->cs_ept)
+ rpmsg_destroy_ept(cport->d_ept);
+ rpmsg_tty_release_cport(cport);
+}
+
+static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
+ { .name = TTY_CH_NAME_RAW },
+ { .name = TTY_CH_NAME_WITH_CTS},
+ { },
+};
+MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
+
+static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
+ .drv.name = KBUILD_MODNAME,
+ .id_table = rpmsg_driver_tty_id_table,
+ .probe = rpmsg_tty_probe,
+ .callback = rpmsg_tty_cb,
+ .remove = rpmsg_tty_remove,
+};
+
+static int __init rpmsg_tty_init(void)
+{
+ int err;
+
+ rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
+ TTY_DRIVER_DYNAMIC_DEV);
+ if (IS_ERR(rpmsg_tty_driver))
+ return PTR_ERR(rpmsg_tty_driver);
+
+ rpmsg_tty_driver->driver_name = "rpmsg_tty";
+ rpmsg_tty_driver->name = "ttyRPMSG";
+ rpmsg_tty_driver->major = 0;
+ rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
+
+ /* Disable unused mode by default */
+ rpmsg_tty_driver->init_termios = tty_std_termios;
+ rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
+ rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
+
+ tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
+
+ err = tty_register_driver(rpmsg_tty_driver);
+ if (err < 0) {
+ pr_err("Couldn't install rpmsg tty driver: err %d\n", err);
+ goto error_put;
+ }
+
+ err = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
+ if (err < 0) {
+ pr_err("Couldn't register rpmsg tty driver: err %d\n", err);
+ goto error_unregister;
+ }
+
+ return 0;
+
+error_unregister:
+ tty_unregister_driver(rpmsg_tty_driver);
+
+error_put:
+ put_tty_driver(rpmsg_tty_driver);
+
+ return err;
+}
+
+static void __exit rpmsg_tty_exit(void)
+{
+ unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
+ tty_unregister_driver(rpmsg_tty_driver);
+ put_tty_driver(rpmsg_tty_driver);
+ idr_destroy(&tty_idr);
+}
+
+module_init(rpmsg_tty_init);
+module_exit(rpmsg_tty_exit);
+
+MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>");
+MODULE_DESCRIPTION("remote processor messaging tty driver");
+MODULE_LICENSE("GPL v2");
--
2.17.1
