Date:   Thu, 4 Apr 2019 18:14:50 +0200
From:   Arnaud Pouliquen <arnaud.pouliquen@...com>
To:     xiang xiao <xiaoxiang781216@...il.com>,
        Fabien Dessenne <fabien.dessenne@...com>
CC:     Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, <linux-kernel@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH 2/2] tty: add rpmsg driver

Hello Xiang,


On 4/3/19 2:47 PM, xiang xiao wrote:
> On Thu, Mar 21, 2019 at 11:48 PM Fabien Dessenne <fabien.dessenne@...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.
The driver is multi-instance based on muti-endpoints on top of the
"rpmsg-tty-channel" service.
On remote side you just have to call rpmsg_create_ept with destination
address set to ANY. The result is a NS service announcement that trigs a
 probe with a new endpoint.
You can find code example for the remote side here:
https://github.com/STMicroelectronics/STM32CubeMP1/blob/master/Projects/STM32MP157C-DK2/Applications/OpenAMP/OpenAMP_TTY_echo/Src/main.c
using some wrapper functions available here:
https://github.com/STMicroelectronics/STM32CubeMP1/tree/master/Middlewares/Third_Party/OpenAMP


Best Regards
Arnaud

> 
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...com>
>> Signed-off-by: Fabien Dessenne <fabien.dessenne@...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@...com> for STMicroelectronics.
>> + *          Fabien Dessenne <fabien.dessenne@...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@...com>");
>> +MODULE_AUTHOR("Fabien Dessenne <fabien.dessenne@...com>");
>> +MODULE_DESCRIPTION("virtio remote processor messaging tty driver");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.7.4
>>

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