Commit 7c0408d8 authored by Arnaud Pouliquen's avatar Arnaud Pouliquen Committed by Greg Kroah-Hartman
Browse files

tty: add rpmsg driver 



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.

Reviewed-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: default avatarArnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20211015094701.5732-3-arnaud.pouliquen@foss.st.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e279317e

drivers/tty/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -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"

drivers/tty/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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/

drivers/tty/rpmsg_tty.c

0 → 100644
+274 −0
Original line number Diff line number Diff line 
// 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_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);

	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_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);

		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@foss.st.com>");

MODULE_DESCRIPTION("remote processor messaging tty driver");

MODULE_LICENSE("GPL v2");