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Subject[PATCH 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>
---
drivers/tty/Kconfig | 9 ++
drivers/tty/Makefile | 1 +
drivers/tty/rpmsg_tty.c | 309 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 319 insertions(+)
create mode 100644 drivers/tty/rpmsg_tty.c

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 0840d27..42696e6 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -441,4 +441,13 @@ config VCC
depends on SUN_LDOMS
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.
endif # TTY
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index c72cafd..90a98a2 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 0000000..9c2a629
--- /dev/null
+++ b/drivers/tty/rpmsg_tty.c
@@ -0,0 +1,309 @@
+// 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.
+ * Derived from the imx-rpmsg and omap-rpmsg implementations.
+ */
+
+#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;
+
+struct rpmsg_tty_port {
+ struct tty_port port; /* TTY port data */
+ unsigned int id; /* TTY rpmsg index */
+ spinlock_t rx_lock; /* message reception lock */
+ struct rpmsg_device *rpdev; /* rpmsg device */
+};
+
+static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
+ void *priv, u32 src)
+{
+ int space;
+ unsigned char *cbuf;
+ struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
+
+ dev_dbg(&rpdev->dev, "msg(<- src 0x%x) len %d\n", src, len);
+
+ print_hex_dump_debug(__func__, DUMP_PREFIX_NONE, 16, 1, data, len,
+ true);
+
+ /* Flush the recv-ed none-zero data to tty node */
+ if (!len)
+ return -EINVAL;
+
+ spin_lock(&cport->rx_lock);
+ space = tty_prepare_flip_string(&cport->port, &cbuf, len);
+ if (space <= 0) {
+ dev_err(&rpdev->dev, "No memory for tty_prepare_flip_string\n");
+ spin_unlock(&cport->rx_lock);
+ return -ENOMEM;
+ }
+
+ if (space != len)
+ dev_warn(&rpdev->dev, "Trunc buffer from %d to %d\n",
+ len, space);
+
+ memcpy(cbuf, data, space);
+ tty_flip_buffer_push(&cport->port);
+ spin_unlock(&cport->rx_lock);
+
+ return 0;
+}
+
+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 unsigned char *buf,
+ int total)
+{
+ int count, ret = 0;
+ const unsigned char *tbuf;
+ struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
+ struct rpmsg_device *rpdev;
+ int msg_size;
+
+ if (!cport) {
+ dev_err(tty->dev, "cannot get cport\n");
+ return -ENODEV;
+ }
+
+ rpdev = cport->rpdev;
+
+ dev_dbg(&rpdev->dev, "%s: send message from tty->index = %d\n",
+ __func__, tty->index);
+
+ if (!buf) {
+ dev_err(&rpdev->dev, "buf shouldn't be null.\n");
+ return -ENOMEM;
+ }
+
+ msg_size = rpmsg_get_buf_payload_size(rpdev->ept);
+ if (msg_size < 0)
+ return msg_size;
+
+ count = total;
+ tbuf = buf;
+ do {
+ /* send a message to our remote processor */
+ ret = rpmsg_send(rpdev->ept, (void *)tbuf,
+ min(count, msg_size));
+ if (ret) {
+ dev_err(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
+ return ret;
+ }
+
+ if (count > msg_size) {
+ count -= msg_size;
+ tbuf += msg_size;
+ } else {
+ count = 0;
+ }
+ } while (count > 0);
+
+ return total;
+}
+
+static int rpmsg_tty_write_room(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;
+ }
+
+ /* report the space in the rpmsg buffer */
+ return rpmsg_get_buf_payload_size(cport->rpdev->ept);
+}
+
+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,
+};
+
+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_probe(struct rpmsg_device *rpdev)
+{
+ struct rpmsg_tty_port *cport;
+ struct device *tty_dev;
+ int ret;
+
+ cport = rpmsg_tty_alloc_cport();
+ if (IS_ERR(cport)) {
+ dev_err(&rpdev->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;
+
+ tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
+ cport->id, &rpdev->dev);
+ if (IS_ERR(tty_dev)) {
+ dev_err(&rpdev->dev, "failed to register tty port\n");
+ ret = PTR_ERR(tty_dev);
+ goto err_destroy;
+ }
+
+ spin_lock_init(&cport->rx_lock);
+ cport->rpdev = rpdev;
+
+ dev_set_drvdata(&rpdev->dev, cport);
+
+ dev_info(&rpdev->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_info(&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;
+ rpmsg_tty_driver->init_termios = tty_std_termios;
+
+ 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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