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Subject[PATCH v3 2/2] tty: add rpmsg driver
Date
This driver exposes a standard tty interface on top of the rpmsg
framework through the "rpmsg-tty-channel" rpmsg service.

This driver supports multi-instances, offering a /dev/ttyRPMSGx entry
per rpmsg endpoint.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
---
Documentation/serial/tty_rpmsg.txt | 38 +++
drivers/tty/Kconfig | 9 +
drivers/tty/Makefile | 1 +
drivers/tty/rpmsg_tty.c | 479 +++++++++++++++++++++++++++++++++++++
4 files changed, 527 insertions(+)
create mode 100644 Documentation/serial/tty_rpmsg.txt
create mode 100644 drivers/tty/rpmsg_tty.c

diff --git a/Documentation/serial/tty_rpmsg.txt b/Documentation/serial/tty_rpmsg.txt
new file mode 100644
index 000000000000..e069ed268a2b
--- /dev/null
+++ b/Documentation/serial/tty_rpmsg.txt
@@ -0,0 +1,38 @@
+
+ The rpmsg TTY
+
+The rpmsg tty driver implements a serial communication on the rpmsg bus,
+to communicate with a remote processor devices in asymmetric multiprocessing
+(AMP) configurations.
+
+The remote processor can instantiate a new tty by requesting a new "rpmsg-tty-channel" RPMsg service. Information related to the RPMsg and
+associated tty device is available in /sys/bus/rpmsg/devices/virtio0.rpmsg-tty-channel.-1.<X>, with
+<X> corresponding to the ttyRPMSG instance.
+
+RPMsg data/control structure
+----------------------------
+
+The RPMsg is used to send data or control messages. Differentiation between the
+stream and the control messages is done thanks to the first byte of the
+RPMsg payload:
+
+
+RPMSG_DATA - rest of messages contains data
+
+RPMSG_CTRL - message contains control.
+
+
+To be compliant with this driver, the remote firmware has to respect this RPMsg
+payload structure. At least the RPMSG_DATA type has to be supported. The
+RPMSG_CTRL is optional.
+
+Flow control type
+-----------------
+
+A minimum flow control can be implemented to allow/block communication with the remote processor.
+
+DATA_TERM_READY - one parameter:
+ - u8 state
+ Set to indicate to remote side that terminal is
+ ready for communication.
+ Reset to block communication with remote side.
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index e0a04bfc873e..d7b426939f69 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -442,6 +442,15 @@ 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 c72cafdf32b4..90a98a20714d 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -33,5 +33,6 @@ 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..c7f53352acb6
--- /dev/null
+++ b/drivers/tty/rpmsg_tty.c
@@ -0,0 +1,479 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STMicroelectronics 2019 - All Rights Reserved
+ * Authors: Arnaud Pouliquen <arnaud.pouliquen@st.com> for STMicroelectronics.
+ * Fabien Dessenne <fabien.dessenne@st.com> 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
+
+static DEFINE_IDR(tty_idr); /* tty instance id */
+static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
+
+static struct tty_driver *rpmsg_tty_driver;
+
+enum rpmsg_tty_type_t {
+ RPMSG_DATA,
+ RPMSG_CTRL,
+ NUM_RPMSG_TTY_TYPE
+};
+
+enum rpmsg_tty_ctrl_t {
+ DATA_TERM_READY, /* ready to accept data */
+ NUM_RPMSG_TTY_CTRL_TYPE
+};
+
+struct rpmsg_tty_payload {
+ u8 cmd;
+ u8 data[0];
+};
+
+struct rpmsg_tty_ctrl {
+ u8 ctrl;
+ u8 values[0];
+};
+
+struct rpmsg_tty_port {
+ struct tty_port port; /* TTY port data */
+ int id; /* TTY rpmsg index */
+ struct rpmsg_device *rpdev; /* rpmsg device */
+ int cts; /* remote reception status */
+};
+
+typedef void (*rpmsg_tty_rx_cb_t)(struct rpmsg_device *, void *, int, void *,
+ u32);
+
+static void rpmsg_tty_data_handler(struct rpmsg_device *rpdev, void *data,
+ int len, void *priv, u32 src)
+{
+ struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
+ u8 *cbuf;
+ int space;
+
+ dev_dbg(&rpdev->dev, "msg(<- src 0x%x) len %d\n", src, len);
+
+ if (!len)
+ return;
+
+ space = tty_prepare_flip_string(&cport->port, &cbuf, len);
+ if (space != len)
+ dev_dbg(&rpdev->dev, "trunc buffer: available space is %d\n",
+ len, space);
+ if (space <= 0)
+ return;
+
+ memcpy(cbuf, data, space);
+ tty_flip_buffer_push(&cport->port);
+}
+
+static void rpmsg_tty_ctrl_handler(struct rpmsg_device *rpdev, void *data,
+ int len, void *priv, u32 src)
+{
+ struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
+ struct rpmsg_tty_ctrl *ctrl = data;
+
+ dev_dbg(&rpdev->dev, "%s: ctrl received %d\n", __func__, ctrl->ctrl);
+ print_hex_dump_debug(__func__, DUMP_PREFIX_NONE, 16, 1, data, len,
+ true);
+
+ if (len <= sizeof(*ctrl)) {
+ dev_err(&rpdev->dev, "%s: ctrl message invalid\n", __func__);
+ return;
+ }
+
+ if (ctrl->ctrl == DATA_TERM_READY) {
+ /* Update the CTS according to remote RTS */
+ if (!ctrl->values[0]) {
+ cport->cts = 0;
+ } else {
+ cport->cts = 1;
+ tty_port_tty_wakeup(&cport->port);
+ }
+ } else {
+ dev_err(&rpdev->dev, "unknown control ID %d\n", ctrl->ctrl);
+ }
+}
+
+static const rpmsg_tty_rx_cb_t rpmsg_tty_handler[] = {
+ [RPMSG_DATA] = rpmsg_tty_data_handler,
+ [RPMSG_CTRL] = rpmsg_tty_ctrl_handler,
+};
+
+static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
+ void *priv, u32 src)
+{
+ struct rpmsg_tty_payload *rbuf = data;
+
+ if (len <= sizeof(*rbuf) || rbuf->cmd > NUM_RPMSG_TTY_TYPE) {
+ dev_err(&rpdev->dev, "Invalid message: size %d, type %d\n",
+ len, rbuf->cmd);
+ return -EINVAL;
+ }
+
+ rpmsg_tty_handler[rbuf->cmd](rpdev, &rbuf->data,
+ len - sizeof(rbuf->cmd), priv, src);
+
+ return 0;
+}
+
+static int rpmsg_tty_write_control(struct tty_struct *tty, u8 ctrl, u8 *values,
+ unsigned int n_value)
+{
+ struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
+ struct rpmsg_tty_payload *msg;
+ struct rpmsg_tty_ctrl *m_ctrl;
+ struct rpmsg_device *rpdev;
+ unsigned int msg_size;
+ int ret;
+
+ if (!cport) {
+ dev_err(tty->dev, "cannot get cport\n");
+ return -ENODEV;
+ }
+
+ rpdev = cport->rpdev;
+
+ msg_size = sizeof(*msg) + sizeof(*m_ctrl) + n_value;
+ msg = kzalloc(msg_size, GFP_KERNEL);
+ if (!msg)
+ return -ENOMEM;
+
+ msg->cmd = RPMSG_CTRL;
+ m_ctrl = (struct rpmsg_tty_ctrl *)&msg->data[0];
+ m_ctrl->ctrl = DATA_TERM_READY;
+ memcpy(m_ctrl->values, values, n_value);
+
+ ret = rpmsg_trysend(rpdev->ept, msg, msg_size);
+ if (ret < 0) {
+ dev_dbg(tty->dev, "cannot send control (%d)\n", ret);
+ ret = 0;
+ }
+ kfree(msg);
+
+ return ret;
+};
+
+static void rpmsg_tty_throttle(struct tty_struct *tty)
+{
+ u8 rts = 0;
+
+ /* Disable remote transmission */
+ rpmsg_tty_write_control(tty, DATA_TERM_READY, &rts, 1);
+};
+
+static void rpmsg_tty_unthrottle(struct tty_struct *tty)
+{
+ u8 rts = 1;
+
+ /* Enable remote transmission */
+ rpmsg_tty_write_control(tty, DATA_TERM_READY, &rts, 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;
+ }
+
+ 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 = idr_find(&tty_idr, tty->index);
+ struct rpmsg_device *rpdev;
+ int msg_size, msg_max_size, ret = 0;
+ int cmd_sz = sizeof(struct rpmsg_tty_payload);
+ u8 *tmpbuf;
+
+ if (!cport) {
+ dev_err(tty->dev, "cannot get cport\n");
+ return -ENODEV;
+ }
+
+ /* 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);
+ if (!buf) {
+ dev_err(&rpdev->dev, "buf shouldn't be null.\n");
+ return -ENOMEM;
+ }
+
+ msg_max_size = rpmsg_get_buf_payload_size(rpdev->ept);
+ if (msg_max_size < 0)
+ return msg_max_size;
+
+ msg_size = min(len + cmd_sz, msg_max_size);
+ tmpbuf = kzalloc(msg_size, GFP_KERNEL);
+ if (!tmpbuf)
+ return -ENOMEM;
+
+ tmpbuf[0] = RPMSG_DATA;
+ memcpy(&tmpbuf[cmd_sz], buf, msg_size - cmd_sz);
+
+ /*
+ * Try to send the message to remote processor, if failed return 0 as
+ * no data sent
+ */
+ ret = rpmsg_trysend(rpdev->ept, (void *)tmpbuf, msg_size);
+ kfree(tmpbuf);
+ if (ret) {
+ dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
+ return 0;
+ }
+
+ return msg_size - sizeof(struct rpmsg_tty_payload);
+}
+
+static int rpmsg_tty_write_room(struct tty_struct *tty)
+{
+ struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
+ int space = 0;
+
+ if (!cport) {
+ dev_err(tty->dev, "cannot get cport\n");
+ return -ENODEV;
+ }
+
+ /*
+ * Report the space in the rpmsg buffer, first byte is reserved to
+ * define the buffer type.
+ */
+ if (cport->cts) {
+ space = rpmsg_get_buf_payload_size(cport->rpdev->ept);
+ space -= sizeof(struct rpmsg_tty_payload);
+ }
+
+ return space;
+}
+
+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)
+{
+ /* 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)
+{
+ struct rpmsg_tty_port *cport =
+ container_of(port, struct rpmsg_tty_port, port);
+
+ pr_debug("%s: dtr_rts state %d\n", __func__, raise);
+ if (!port->tty || !cport) {
+ pr_err("invalid port\n");
+ return;
+ }
+
+ cport->cts = 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 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);
+ }
+
+ tty_port_init(&cport->port);
+ cport->port.low_latency = cport->port.flags | ASYNC_LOW_LATENCY;
+ 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);
+ 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);
+ rpmsg_tty_release_cport(cport);
+}
+
+static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
+ { .name = "rpmsg-tty-channel" },
+ { },
+};
+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@st.com>");
+MODULE_AUTHOR("Fabien Dessenne <fabien.dessenne@st.com>");
+MODULE_DESCRIPTION("virtio remote processor messaging tty driver");
+MODULE_LICENSE("GPL v2");
--
2.7.4
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