Hello Mathieu,
On 10/12/21 8:07 PM, Mathieu Poirier wrote:
> On Fri, Oct 08, 2021 at 05:34:46PM +0200, Arnaud Pouliquen wrote:
>> This driver exposes a standard TTY interface on top of the rpmsg
>> framework through a rpmsg service.
>>
>> This driver supports multi-instances, offering a /dev/ttyRPMSGx entry
>> per rpmsg endpoint.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
>>
>> ---
>> Update from V8
>> => Update based on Greg Greg Kroah-Hartman comments:
>> - add module name in kconfig
>> - remove the tty_rpmsg.rst documentation file and add description in
>> rpmsg_tty.c.
>> - rpmsg_tty.c remove of useless check and logs.
>> - print err log instead of debug log on truncated RX buffer.
>> ---
>> drivers/tty/Kconfig | 12 ++
>> drivers/tty/Makefile | 1 +
>> drivers/tty/rpmsg_tty.c | 275 ++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 288 insertions(+)
>> create mode 100644 drivers/tty/rpmsg_tty.c
>>
>> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
>> index 23cc988c68a4..cc30ff93e2e4 100644
>> --- a/drivers/tty/Kconfig
>> +++ b/drivers/tty/Kconfig
>> @@ -368,6 +368,18 @@ config VCC
>>
>> source "drivers/tty/hvc/Kconfig"
>>
>> +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.
>> +
>> + To compile this driver as a module, choose M here: the module will be
>> + called rpmsg_tty.
>> +
>> endif # TTY
>>
>> source "drivers/tty/serdev/Kconfig"
>> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
>> index a2bd75fbaaa4..07aca5184a55 100644
>> --- a/drivers/tty/Makefile
>> +++ b/drivers/tty/Makefile
>> @@ -26,5 +26,6 @@ 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..226a13f6ef94
>> --- /dev/null
>> +++ b/drivers/tty/rpmsg_tty.c
>> @@ -0,0 +1,275 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2021 STMicroelectronics - All Rights Reserved
>> + *
>> + * The rpmsg tty driver implements serial communication on the RPMsg bus to makes
>> + * possible for user-space programs to send and receive rpmsg messages as a standard
>> + * tty protocol.
>> + *
>> + * The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
>> + * The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
>> + */
>> +
>> +#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 */
>> + int id; /* TTY rpmsg index */
>> + struct rpmsg_device *rpdev; /* rpmsg device */
>> +};
>> +
>> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
>> +{
>> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
>> + int copied;
>> +
>> + if (!len)
>> + return -EINVAL;
>> + copied = tty_insert_flip_string(&cport->port, data, len);
>> + if (copied != len)
>> + dev_err(&rpdev->dev, "Trunc buffer: available space is %d\n",
>> + copied);
Here as the rpmsg callback return is not tested we need to log something because
data is lost. I will add the ratelimited version to limit logs.
>> + tty_flip_buffer_push(&cport->port);
>> +
>> + 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);
>> +
>> + tty->driver_data = cport;
>> +
>> + 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 = tty->driver_data;
>> + struct rpmsg_device *rpdev;
>> + int msg_max_size, msg_size;
>> + int ret;
>> +
>> + rpdev = cport->rpdev;
>> +
>> + msg_max_size = rpmsg_get_mtu(rpdev->ept);
>> + if (msg_max_size < 0)
>> + return msg_max_size;
>> +
>> + msg_size = min(len, msg_max_size);
>> +
>> + /*
>> + * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
>> + * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
>> + */
>> + ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
>> + if (ret) {
>> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
>
> I'm with Greg on this one. Event if it's a dev_dbg() something like this could
> quickly fill the logs.
That's right,if the remote side is stalled and application doesn't propertly
handle the error returned.
> Customers should learn to use ftrace. At the very least
> please use the ratelimited() version. Same comment applies to rpmsg_tty_cb().
I'm not yet an expert in ftrace, I don't see trace that would highligth this
error (return value not traced), except adding trace_printk. If you have a
solution, please could you point that out to me?
The goal here is that a customers (who has an user spece application develloper
profile) has the explicit information that something goes wrong.
By default I would be in favour of using ratelimited version also here.
>
> Otherwise:
>
> Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
>
Thanks,
Arnaud
>> + return ret;
>> + }
>> +
>> + return msg_size;
>> +}
>> +
>> +static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
>> +{
>> + struct rpmsg_tty_port *cport = tty->driver_data;
>> + int size;
>> +
>> + size = rpmsg_get_mtu(cport->rpdev->ept);
>> + if (size < 0)
>> + return 0;
>> +
>> + return size;
>> +}
>> +
>> +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,
>> +};
>> +
>> +static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
>> +{
>> + struct rpmsg_tty_port *cport;
>> + int err;
>> +
>> + 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) {
>> + err = cport->id;
>> + kfree(cport);
>> + return ERR_PTR(err);
>> + }
>> +
>> + 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 const struct tty_port_operations rpmsg_tty_port_ops = { };
>> +
>> +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.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" },
>> + { },
>> +};
>> +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:
>> + tty_driver_kref_put(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);
>> + tty_driver_kref_put(rpmsg_tty_driver);
>> + idr_destroy(&tty_idr);
>> +}
>> +
>> +module_init(rpmsg_tty_init);
>> +module_exit(rpmsg_tty_exit);
>> +
>> +MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>");
>> +MODULE_DESCRIPTION("remote processor messaging tty driver");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.17.1
>>
