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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: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com> Link: https://lore.kernel.org/r/20211015094701.5732-3-arnaud.pouliquen@foss.st.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -368,6 +368,18 @@ config VCC
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source "drivers/tty/hvc/Kconfig"
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config RPMSG_TTY
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tristate "RPMSG tty driver"
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depends on RPMSG
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help
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Say y here to export rpmsg endpoints as tty devices, usually found
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in /dev/ttyRPMSGx.
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This makes it possible for user-space programs to send and receive
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rpmsg messages as a standard tty protocol.
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To compile this driver as a module, choose M here: the module will be
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called rpmsg_tty.
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endif # TTY
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source "drivers/tty/serdev/Kconfig"
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@ -26,5 +26,6 @@ obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o
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obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o
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obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
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obj-$(CONFIG_VCC) += vcc.o
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obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o
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obj-y += ipwireless/
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274
drivers/tty/rpmsg_tty.c
Normal file
274
drivers/tty/rpmsg_tty.c
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@ -0,0 +1,274 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2021 STMicroelectronics - All Rights Reserved
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*
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* The rpmsg tty driver implements serial communication on the RPMsg bus to makes
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* possible for user-space programs to send and receive rpmsg messages as a standard
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* tty protocol.
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*
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* The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service.
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* The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented yet.
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*/
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#include <linux/module.h>
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#include <linux/rpmsg.h>
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#include <linux/slab.h>
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#include <linux/tty.h>
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#include <linux/tty_flip.h>
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#define MAX_TTY_RPMSG 32
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static DEFINE_IDR(tty_idr); /* tty instance id */
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static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
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static struct tty_driver *rpmsg_tty_driver;
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struct rpmsg_tty_port {
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struct tty_port port; /* TTY port data */
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int id; /* TTY rpmsg index */
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struct rpmsg_device *rpdev; /* rpmsg device */
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};
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static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src)
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{
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struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
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int copied;
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if (!len)
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return -EINVAL;
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copied = tty_insert_flip_string(&cport->port, data, len);
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if (copied != len)
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dev_err_ratelimited(&rpdev->dev, "Trunc buffer: available space is %d\n", copied);
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tty_flip_buffer_push(&cport->port);
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return 0;
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}
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static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
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{
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struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
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tty->driver_data = cport;
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return tty_port_install(&cport->port, driver, tty);
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}
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static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
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{
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return tty_port_open(tty->port, tty, filp);
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}
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static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
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{
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return tty_port_close(tty->port, tty, filp);
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}
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static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
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{
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struct rpmsg_tty_port *cport = tty->driver_data;
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struct rpmsg_device *rpdev;
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int msg_max_size, msg_size;
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int ret;
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rpdev = cport->rpdev;
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msg_max_size = rpmsg_get_mtu(rpdev->ept);
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if (msg_max_size < 0)
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return msg_max_size;
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msg_size = min(len, msg_max_size);
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/*
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* Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not
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* hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM.
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*/
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ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size);
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if (ret) {
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dev_dbg_ratelimited(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
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return ret;
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}
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return msg_size;
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}
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static unsigned int rpmsg_tty_write_room(struct tty_struct *tty)
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{
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struct rpmsg_tty_port *cport = tty->driver_data;
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int size;
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size = rpmsg_get_mtu(cport->rpdev->ept);
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if (size < 0)
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return 0;
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return size;
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}
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static const struct tty_operations rpmsg_tty_ops = {
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.install = rpmsg_tty_install,
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.open = rpmsg_tty_open,
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.close = rpmsg_tty_close,
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.write = rpmsg_tty_write,
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.write_room = rpmsg_tty_write_room,
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};
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static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
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{
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struct rpmsg_tty_port *cport;
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int err;
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cport = kzalloc(sizeof(*cport), GFP_KERNEL);
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if (!cport)
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return ERR_PTR(-ENOMEM);
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mutex_lock(&idr_lock);
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cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
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mutex_unlock(&idr_lock);
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if (cport->id < 0) {
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err = cport->id;
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kfree(cport);
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return ERR_PTR(err);
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}
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return cport;
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}
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static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport)
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{
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mutex_lock(&idr_lock);
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idr_remove(&tty_idr, cport->id);
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mutex_unlock(&idr_lock);
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kfree(cport);
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}
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static const struct tty_port_operations rpmsg_tty_port_ops = { };
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static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
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{
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struct rpmsg_tty_port *cport;
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struct device *dev = &rpdev->dev;
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struct device *tty_dev;
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int ret;
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cport = rpmsg_tty_alloc_cport();
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if (IS_ERR(cport)) {
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dev_err(dev, "Failed to alloc tty port\n");
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return PTR_ERR(cport);
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}
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tty_port_init(&cport->port);
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cport->port.ops = &rpmsg_tty_port_ops;
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tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
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cport->id, dev);
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if (IS_ERR(tty_dev)) {
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dev_err(dev, "Failed to register tty port\n");
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ret = PTR_ERR(tty_dev);
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goto err_destroy;
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}
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cport->rpdev = rpdev;
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dev_set_drvdata(dev, cport);
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dev_dbg(dev, "New channel: 0x%x -> 0x%x : ttyRPMSG%d\n",
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rpdev->src, rpdev->dst, cport->id);
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return 0;
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err_destroy:
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tty_port_destroy(&cport->port);
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rpmsg_tty_release_cport(cport);
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return ret;
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}
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static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
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{
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struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
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dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id);
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/* User hang up to release the tty */
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if (tty_port_initialized(&cport->port))
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tty_port_tty_hangup(&cport->port, false);
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tty_unregister_device(rpmsg_tty_driver, cport->id);
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tty_port_destroy(&cport->port);
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rpmsg_tty_release_cport(cport);
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}
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static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
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{ .name = "rpmsg-tty" },
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{ },
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};
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MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
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static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
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.drv.name = KBUILD_MODNAME,
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.id_table = rpmsg_driver_tty_id_table,
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.probe = rpmsg_tty_probe,
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.callback = rpmsg_tty_cb,
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.remove = rpmsg_tty_remove,
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};
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static int __init rpmsg_tty_init(void)
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{
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int err;
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rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
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TTY_DRIVER_DYNAMIC_DEV);
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if (IS_ERR(rpmsg_tty_driver))
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return PTR_ERR(rpmsg_tty_driver);
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rpmsg_tty_driver->driver_name = "rpmsg_tty";
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rpmsg_tty_driver->name = "ttyRPMSG";
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rpmsg_tty_driver->major = 0;
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rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
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/* Disable unused mode by default */
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rpmsg_tty_driver->init_termios = tty_std_termios;
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rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
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rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
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tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
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err = tty_register_driver(rpmsg_tty_driver);
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if (err < 0) {
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pr_err("Couldn't install rpmsg tty driver: err %d\n", err);
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goto error_put;
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}
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err = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
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if (err < 0) {
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pr_err("Couldn't register rpmsg tty driver: err %d\n", err);
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goto error_unregister;
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}
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return 0;
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error_unregister:
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tty_unregister_driver(rpmsg_tty_driver);
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error_put:
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tty_driver_kref_put(rpmsg_tty_driver);
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return err;
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}
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static void __exit rpmsg_tty_exit(void)
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{
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unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
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tty_unregister_driver(rpmsg_tty_driver);
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tty_driver_kref_put(rpmsg_tty_driver);
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idr_destroy(&tty_idr);
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}
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module_init(rpmsg_tty_init);
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module_exit(rpmsg_tty_exit);
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MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>");
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MODULE_DESCRIPTION("remote processor messaging tty driver");
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MODULE_LICENSE("GPL v2");
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