Re: [PATCH 2/2] tty: add rpmsg driver

[Arnaud Pouliquen]

On 4/5/19 12:12 PM, xiang xiao wrote:
> On Fri, Apr 5, 2019 at 12:14 AM Arnaud Pouliquen
> <arnaud.pouliquen@xxxxxx> wrote:
>>
>> 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@xxxxxx> 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
> 
> Demo code create two uarts(huart0 and huart1), and both use the same
> channel name( "rpmsg-tty-channel").
> But rpmsg_create_channel in kernel will complain the duplication:
> /* make sure a similar channel doesn't already exist */
> tmp = rpmsg_find_device(dev, chinfo);
> if (tmp) {
>         /* decrement the matched device's refcount back */
>         put_device(tmp);
>         dev_err(dev, "channel %s:%x:%x already exist\n",
>                    chinfo->name, chinfo->src, chinfo->dst);
>         return NULL;
> }
> Do you have some local change not upstream yet?
Nothing is missing. There is no complain as the function
rpmsg_device_match returns 0, because the chinfo->dst (that corresponds
to the remote ept address) is different.

If i well remember you have also a similar implementation of the service
on your side. Do you see any incompatibility with your implementation?

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