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SubjectRe: [PATCH 2/2] tty: add rpmsg driver
On Thu, Mar 21, 2019 at 11:48 PM Fabien Dessenne <fabien.dessenne@st.com> wrote:
>
> 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.
>

How to support multi-instances from the same remoteproc instance? I
saw that the channel name is fixed to "rpmsg-tty-channel" which mean
only one channel can be created for each remote side.

> 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);
> +

We need the flow control(or handshake) here, otherwise it's very easy
to lose the data if kernel keep send the data as fast as possible.

> + 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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