Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 796 insertions, 0 deletions

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
new file mode 100644
index 000000000..dce08a6d7
--- /dev/null
+++ b/drivers/tty/tty_port.c
@@ -0,0 +1,796 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Tty port functions
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/serial.h>
+#include <linux/timer.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/serdev.h>
+#include "tty.h"
+
+static int tty_port_default_receive_buf(struct tty_port *port,
+					const unsigned char *p,
+					const unsigned char *f, size_t count)
+{
+	int ret;
+	struct tty_struct *tty;
+	struct tty_ldisc *disc;
+
+	tty = READ_ONCE(port->itty);
+	if (!tty)
+		return 0;
+
+	disc = tty_ldisc_ref(tty);
+	if (!disc)
+		return 0;
+
+	ret = tty_ldisc_receive_buf(disc, p, (char *)f, count);
+
+	tty_ldisc_deref(disc);
+
+	return ret;
+}
+
+static void tty_port_default_lookahead_buf(struct tty_port *port, const unsigned char *p,
+					   const unsigned char *f, unsigned int count)
+{
+	struct tty_struct *tty;
+	struct tty_ldisc *disc;
+
+	tty = READ_ONCE(port->itty);
+	if (!tty)
+		return;
+
+	disc = tty_ldisc_ref(tty);
+	if (!disc)
+		return;
+
+	if (disc->ops->lookahead_buf)
+		disc->ops->lookahead_buf(disc->tty, p, f, count);
+
+	tty_ldisc_deref(disc);
+}
+
+static void tty_port_default_wakeup(struct tty_port *port)
+{
+	struct tty_struct *tty = tty_port_tty_get(port);
+
+	if (tty) {
+		tty_wakeup(tty);
+		tty_kref_put(tty);
+	}
+}
+
+const struct tty_port_client_operations tty_port_default_client_ops = {
+	.receive_buf = tty_port_default_receive_buf,
+	.lookahead_buf = tty_port_default_lookahead_buf,
+	.write_wakeup = tty_port_default_wakeup,
+};
+EXPORT_SYMBOL_GPL(tty_port_default_client_ops);
+
+/**
+ * tty_port_init -- initialize tty_port
+ * @port: tty_port to initialize
+ *
+ * Initializes the state of struct tty_port. When a port was initialized using
+ * this function, one has to destroy the port by tty_port_destroy(). Either
+ * indirectly by using &tty_port refcounting (tty_port_put()) or directly if
+ * refcounting is not used.
+ */
+void tty_port_init(struct tty_port *port)
+{
+	memset(port, 0, sizeof(*port));
+	tty_buffer_init(port);
+	init_waitqueue_head(&port->open_wait);
+	init_waitqueue_head(&port->delta_msr_wait);
+	mutex_init(&port->mutex);
+	mutex_init(&port->buf_mutex);
+	spin_lock_init(&port->lock);
+	port->close_delay = (50 * HZ) / 100;
+	port->closing_wait = (3000 * HZ) / 100;
+	port->client_ops = &tty_port_default_client_ops;
+	kref_init(&port->kref);
+}
+EXPORT_SYMBOL(tty_port_init);
+
+/**
+ * tty_port_link_device - link tty and tty_port
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ *
+ * Provide the tty layer with a link from a tty (specified by @index) to a
+ * tty_port (@port). Use this only if neither tty_port_register_device() nor
+ * tty_port_install() is used in the driver. If used, this has to be called
+ * before tty_register_driver().
+ */
+void tty_port_link_device(struct tty_port *port,
+		struct tty_driver *driver, unsigned index)
+{
+	if (WARN_ON(index >= driver->num))
+		return;
+	driver->ports[index] = port;
+}
+EXPORT_SYMBOL_GPL(tty_port_link_device);
+
+/**
+ * tty_port_register_device - register tty device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ *
+ * It is the same as tty_register_device() except the provided @port is linked
+ * to a concrete tty specified by @index. Use this or tty_port_install() (or
+ * both). Call tty_port_link_device() as a last resort.
+ */
+struct device *tty_port_register_device(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device)
+{
+	return tty_port_register_device_attr(port, driver, index, device, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device);
+
+/**
+ * tty_port_register_device_attr - register tty device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ * @drvdata: Driver data to be set to device.
+ * @attr_grp: Attribute group to be set on device.
+ *
+ * It is the same as tty_register_device_attr() except the provided @port is
+ * linked to a concrete tty specified by @index. Use this or tty_port_install()
+ * (or both). Call tty_port_link_device() as a last resort.
+ */
+struct device *tty_port_register_device_attr(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device, void *drvdata,
+		const struct attribute_group **attr_grp)
+{
+	tty_port_link_device(port, driver, index);
+	return tty_register_device_attr(driver, index, device, drvdata,
+			attr_grp);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
+
+/**
+ * tty_port_register_device_attr_serdev - register tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ * @drvdata: driver data for the device
+ * @attr_grp: attribute group for the device
+ *
+ * Register a serdev or tty device depending on if the parent device has any
+ * defined serdev clients or not.
+ */
+struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device, void *drvdata,
+		const struct attribute_group **attr_grp)
+{
+	struct device *dev;
+
+	tty_port_link_device(port, driver, index);
+
+	dev = serdev_tty_port_register(port, device, driver, index);
+	if (PTR_ERR(dev) != -ENODEV) {
+		/* Skip creating cdev if we registered a serdev device */
+		return dev;
+	}
+
+	return tty_register_device_attr(driver, index, device, drvdata,
+			attr_grp);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev);
+
+/**
+ * tty_port_register_device_serdev - register tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ *
+ * Register a serdev or tty device depending on if the parent device has any
+ * defined serdev clients or not.
+ */
+struct device *tty_port_register_device_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device)
+{
+	return tty_port_register_device_attr_serdev(port, driver, index,
+			device, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device_serdev);
+
+/**
+ * tty_port_unregister_device - deregister a tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ *
+ * If a tty or serdev device is registered with a call to
+ * tty_port_register_device_serdev() then this function must be called when
+ * the device is gone.
+ */
+void tty_port_unregister_device(struct tty_port *port,
+		struct tty_driver *driver, unsigned index)
+{
+	int ret;
+
+	ret = serdev_tty_port_unregister(port);
+	if (ret == 0)
+		return;
+
+	tty_unregister_device(driver, index);
+}
+EXPORT_SYMBOL_GPL(tty_port_unregister_device);
+
+int tty_port_alloc_xmit_buf(struct tty_port *port)
+{
+	/* We may sleep in get_zeroed_page() */
+	mutex_lock(&port->buf_mutex);
+	if (port->xmit_buf == NULL) {
+		port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+		if (port->xmit_buf)
+			kfifo_init(&port->xmit_fifo, port->xmit_buf, PAGE_SIZE);
+	}
+	mutex_unlock(&port->buf_mutex);
+	if (port->xmit_buf == NULL)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
+
+void tty_port_free_xmit_buf(struct tty_port *port)
+{
+	mutex_lock(&port->buf_mutex);
+	free_page((unsigned long)port->xmit_buf);
+	port->xmit_buf = NULL;
+	INIT_KFIFO(port->xmit_fifo);
+	mutex_unlock(&port->buf_mutex);
+}
+EXPORT_SYMBOL(tty_port_free_xmit_buf);
+
+/**
+ * tty_port_destroy -- destroy inited port
+ * @port: tty port to be destroyed
+ *
+ * When a port was initialized using tty_port_init(), one has to destroy the
+ * port by this function. Either indirectly by using &tty_port refcounting
+ * (tty_port_put()) or directly if refcounting is not used.
+ */
+void tty_port_destroy(struct tty_port *port)
+{
+	tty_buffer_cancel_work(port);
+	tty_buffer_free_all(port);
+}
+EXPORT_SYMBOL(tty_port_destroy);
+
+static void tty_port_destructor(struct kref *kref)
+{
+	struct tty_port *port = container_of(kref, struct tty_port, kref);
+
+	/* check if last port ref was dropped before tty release */
+	if (WARN_ON(port->itty))
+		return;
+	free_page((unsigned long)port->xmit_buf);
+	tty_port_destroy(port);
+	if (port->ops && port->ops->destruct)
+		port->ops->destruct(port);
+	else
+		kfree(port);
+}
+
+/**
+ * tty_port_put -- drop a reference to tty_port
+ * @port: port to drop a reference of (can be NULL)
+ *
+ * The final put will destroy and free up the @port using
+ * @port->ops->destruct() hook, or using kfree() if not provided.
+ */
+void tty_port_put(struct tty_port *port)
+{
+	if (port)
+		kref_put(&port->kref, tty_port_destructor);
+}
+EXPORT_SYMBOL(tty_port_put);
+
+/**
+ * tty_port_tty_get	-	get a tty reference
+ * @port: tty port
+ *
+ * Return a refcount protected tty instance or %NULL if the port is not
+ * associated with a tty (eg due to close or hangup).
+ */
+struct tty_struct *tty_port_tty_get(struct tty_port *port)
+{
+	unsigned long flags;
+	struct tty_struct *tty;
+
+	spin_lock_irqsave(&port->lock, flags);
+	tty = tty_kref_get(port->tty);
+	spin_unlock_irqrestore(&port->lock, flags);
+	return tty;
+}
+EXPORT_SYMBOL(tty_port_tty_get);
+
+/**
+ * tty_port_tty_set	-	set the tty of a port
+ * @port: tty port
+ * @tty: the tty
+ *
+ * Associate the port and tty pair. Manages any internal refcounts. Pass %NULL
+ * to deassociate a port.
+ */
+void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	tty_kref_put(port->tty);
+	port->tty = tty_kref_get(tty);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+EXPORT_SYMBOL(tty_port_tty_set);
+
+/**
+ * tty_port_shutdown - internal helper to shutdown the device
+ * @port: tty port to be shut down
+ * @tty: the associated tty
+ *
+ * It is used by tty_port_hangup() and tty_port_close(). Its task is to
+ * shutdown the device if it was initialized (note consoles remain
+ * functioning). It lowers DTR/RTS (if @tty has HUPCL set) and invokes
+ * @port->ops->shutdown().
+ */
+static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty)
+{
+	mutex_lock(&port->mutex);
+	if (port->console)
+		goto out;
+
+	if (tty_port_initialized(port)) {
+		tty_port_set_initialized(port, 0);
+		/*
+		 * Drop DTR/RTS if HUPCL is set. This causes any attached
+		 * modem to hang up the line.
+		 */
+		if (tty && C_HUPCL(tty))
+			tty_port_lower_dtr_rts(port);
+
+		if (port->ops->shutdown)
+			port->ops->shutdown(port);
+	}
+out:
+	mutex_unlock(&port->mutex);
+}
+
+/**
+ * tty_port_hangup		-	hangup helper
+ * @port: tty port
+ *
+ * Perform port level tty hangup flag and count changes. Drop the tty
+ * reference.
+ *
+ * Caller holds tty lock.
+ */
+void tty_port_hangup(struct tty_port *port)
+{
+	struct tty_struct *tty;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	port->count = 0;
+	tty = port->tty;
+	if (tty)
+		set_bit(TTY_IO_ERROR, &tty->flags);
+	port->tty = NULL;
+	spin_unlock_irqrestore(&port->lock, flags);
+	tty_port_set_active(port, 0);
+	tty_port_shutdown(port, tty);
+	tty_kref_put(tty);
+	wake_up_interruptible(&port->open_wait);
+	wake_up_interruptible(&port->delta_msr_wait);
+}
+EXPORT_SYMBOL(tty_port_hangup);
+
+/**
+ * tty_port_tty_hangup - helper to hang up a tty
+ * @port: tty port
+ * @check_clocal: hang only ttys with %CLOCAL unset?
+ */
+void tty_port_tty_hangup(struct tty_port *port, bool check_clocal)
+{
+	struct tty_struct *tty = tty_port_tty_get(port);
+
+	if (tty && (!check_clocal || !C_CLOCAL(tty)))
+		tty_hangup(tty);
+	tty_kref_put(tty);
+}
+EXPORT_SYMBOL_GPL(tty_port_tty_hangup);
+
+/**
+ * tty_port_tty_wakeup - helper to wake up a tty
+ * @port: tty port
+ */
+void tty_port_tty_wakeup(struct tty_port *port)
+{
+	port->client_ops->write_wakeup(port);
+}
+EXPORT_SYMBOL_GPL(tty_port_tty_wakeup);
+
+/**
+ * tty_port_carrier_raised	-	carrier raised check
+ * @port: tty port
+ *
+ * Wrapper for the carrier detect logic. For the moment this is used
+ * to hide some internal details. This will eventually become entirely
+ * internal to the tty port.
+ */
+int tty_port_carrier_raised(struct tty_port *port)
+{
+	if (port->ops->carrier_raised == NULL)
+		return 1;
+	return port->ops->carrier_raised(port);
+}
+EXPORT_SYMBOL(tty_port_carrier_raised);
+
+/**
+ * tty_port_raise_dtr_rts	-	Raise DTR/RTS
+ * @port: tty port
+ *
+ * Wrapper for the DTR/RTS raise logic. For the moment this is used to hide
+ * some internal details. This will eventually become entirely internal to the
+ * tty port.
+ */
+void tty_port_raise_dtr_rts(struct tty_port *port)
+{
+	if (port->ops->dtr_rts)
+		port->ops->dtr_rts(port, 1);
+}
+EXPORT_SYMBOL(tty_port_raise_dtr_rts);
+
+/**
+ * tty_port_lower_dtr_rts	-	Lower DTR/RTS
+ * @port: tty port
+ *
+ * Wrapper for the DTR/RTS raise logic. For the moment this is used to hide
+ * some internal details. This will eventually become entirely internal to the
+ * tty port.
+ */
+void tty_port_lower_dtr_rts(struct tty_port *port)
+{
+	if (port->ops->dtr_rts)
+		port->ops->dtr_rts(port, 0);
+}
+EXPORT_SYMBOL(tty_port_lower_dtr_rts);
+
+/**
+ * tty_port_block_til_ready	-	Waiting logic for tty open
+ * @port: the tty port being opened
+ * @tty: the tty device being bound
+ * @filp: the file pointer of the opener or %NULL
+ *
+ * Implement the core POSIX/SuS tty behaviour when opening a tty device.
+ * Handles:
+ *
+ *	- hangup (both before and during)
+ *	- non blocking open
+ *	- rts/dtr/dcd
+ *	- signals
+ *	- port flags and counts
+ *
+ * The passed @port must implement the @port->ops->carrier_raised method if it
+ * can do carrier detect and the @port->ops->dtr_rts method if it supports
+ * software management of these lines. Note that the dtr/rts raise is done each
+ * iteration as a hangup may have previously dropped them while we wait.
+ *
+ * Caller holds tty lock.
+ *
+ * Note: May drop and reacquire tty lock when blocking, so @tty and @port may
+ * have changed state (eg., may have been hung up).
+ */
+int tty_port_block_til_ready(struct tty_port *port,
+				struct tty_struct *tty, struct file *filp)
+{
+	int do_clocal = 0, retval;
+	unsigned long flags;
+	DEFINE_WAIT(wait);
+
+	/* if non-blocking mode is set we can pass directly to open unless
+	 * the port has just hung up or is in another error state.
+	 */
+	if (tty_io_error(tty)) {
+		tty_port_set_active(port, 1);
+		return 0;
+	}
+	if (filp == NULL || (filp->f_flags & O_NONBLOCK)) {
+		/* Indicate we are open */
+		if (C_BAUD(tty))
+			tty_port_raise_dtr_rts(port);
+		tty_port_set_active(port, 1);
+		return 0;
+	}
+
+	if (C_CLOCAL(tty))
+		do_clocal = 1;
+
+	/* Block waiting until we can proceed. We may need to wait for the
+	 * carrier, but we must also wait for any close that is in progress
+	 * before the next open may complete.
+	 */
+
+	retval = 0;
+
+	/* The port lock protects the port counts */
+	spin_lock_irqsave(&port->lock, flags);
+	port->count--;
+	port->blocked_open++;
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	while (1) {
+		/* Indicate we are open */
+		if (C_BAUD(tty) && tty_port_initialized(port))
+			tty_port_raise_dtr_rts(port);
+
+		prepare_to_wait(&port->open_wait, &wait, TASK_INTERRUPTIBLE);
+		/* Check for a hangup or uninitialised port.
+		 * Return accordingly.
+		 */
+		if (tty_hung_up_p(filp) || !tty_port_initialized(port)) {
+			if (port->flags & ASYNC_HUP_NOTIFY)
+				retval = -EAGAIN;
+			else
+				retval = -ERESTARTSYS;
+			break;
+		}
+		/*
+		 * Probe the carrier. For devices with no carrier detect
+		 * tty_port_carrier_raised will always return true.
+		 * Never ask drivers if CLOCAL is set, this causes troubles
+		 * on some hardware.
+		 */
+		if (do_clocal || tty_port_carrier_raised(port))
+			break;
+		if (signal_pending(current)) {
+			retval = -ERESTARTSYS;
+			break;
+		}
+		tty_unlock(tty);
+		schedule();
+		tty_lock(tty);
+	}
+	finish_wait(&port->open_wait, &wait);
+
+	/* Update counts. A parallel hangup will have set count to zero and
+	 * we must not mess that up further.
+	 */
+	spin_lock_irqsave(&port->lock, flags);
+	if (!tty_hung_up_p(filp))
+		port->count++;
+	port->blocked_open--;
+	spin_unlock_irqrestore(&port->lock, flags);
+	if (retval == 0)
+		tty_port_set_active(port, 1);
+	return retval;
+}
+EXPORT_SYMBOL(tty_port_block_til_ready);
+
+static void tty_port_drain_delay(struct tty_port *port, struct tty_struct *tty)
+{
+	unsigned int bps = tty_get_baud_rate(tty);
+	long timeout;
+
+	if (bps > 1200) {
+		timeout = (HZ * 10 * port->drain_delay) / bps;
+		timeout = max_t(long, timeout, HZ / 10);
+	} else {
+		timeout = 2 * HZ;
+	}
+	schedule_timeout_interruptible(timeout);
+}
+
+/**
+ * tty_port_close_start - helper for tty->ops->close, part 1/2
+ * @port: tty_port of the device
+ * @tty: tty being closed
+ * @filp: passed file pointer
+ *
+ * Decrements and checks open count. Flushes the port if this is the last
+ * close. That means, dropping the data from the outpu buffer on the device and
+ * waiting for sending logic to finish. The rest of close handling is performed
+ * in tty_port_close_end().
+ *
+ * Locking: Caller holds tty lock.
+ *
+ * Return: 1 if this is the last close, otherwise 0
+ */
+int tty_port_close_start(struct tty_port *port,
+				struct tty_struct *tty, struct file *filp)
+{
+	unsigned long flags;
+
+	if (tty_hung_up_p(filp))
+		return 0;
+
+	spin_lock_irqsave(&port->lock, flags);
+	if (tty->count == 1 && port->count != 1) {
+		tty_warn(tty, "%s: tty->count = 1 port count = %d\n", __func__,
+			 port->count);
+		port->count = 1;
+	}
+	if (--port->count < 0) {
+		tty_warn(tty, "%s: bad port count (%d)\n", __func__,
+			 port->count);
+		port->count = 0;
+	}
+
+	if (port->count) {
+		spin_unlock_irqrestore(&port->lock, flags);
+		return 0;
+	}
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	tty->closing = 1;
+
+	if (tty_port_initialized(port)) {
+		/* Don't block on a stalled port, just pull the chain */
+		if (tty->flow.tco_stopped)
+			tty_driver_flush_buffer(tty);
+		if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
+			tty_wait_until_sent(tty, port->closing_wait);
+		if (port->drain_delay)
+			tty_port_drain_delay(port, tty);
+	}
+	/* Flush the ldisc buffering */
+	tty_ldisc_flush(tty);
+
+	/* Report to caller this is the last port reference */
+	return 1;
+}
+EXPORT_SYMBOL(tty_port_close_start);
+
+/**
+ * tty_port_close_end - helper for tty->ops->close, part 2/2
+ * @port: tty_port of the device
+ * @tty: tty being closed
+ *
+ * This is a continuation of the first part: tty_port_close_start(). This
+ * should be called after turning off the device. It flushes the data from the
+ * line discipline and delays the close by @port->close_delay.
+ *
+ * Locking: Caller holds tty lock.
+ */
+void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
+{
+	unsigned long flags;
+
+	tty_ldisc_flush(tty);
+	tty->closing = 0;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (port->blocked_open) {
+		spin_unlock_irqrestore(&port->lock, flags);
+		if (port->close_delay)
+			msleep_interruptible(jiffies_to_msecs(port->close_delay));
+		spin_lock_irqsave(&port->lock, flags);
+		wake_up_interruptible(&port->open_wait);
+	}
+	spin_unlock_irqrestore(&port->lock, flags);
+	tty_port_set_active(port, 0);
+}
+EXPORT_SYMBOL(tty_port_close_end);
+
+/**
+ * tty_port_close - generic tty->ops->close handler
+ * @port: tty_port of the device
+ * @tty: tty being closed
+ * @filp: passed file pointer
+ *
+ * It is a generic helper to be used in driver's @tty->ops->close. It wraps a
+ * sequence of tty_port_close_start(), tty_port_shutdown(), and
+ * tty_port_close_end(). The latter two are called only if this is the last
+ * close. See the respective functions for the details.
+ *
+ * Locking: Caller holds tty lock
+ */
+void tty_port_close(struct tty_port *port, struct tty_struct *tty,
+							struct file *filp)
+{
+	if (tty_port_close_start(port, tty, filp) == 0)
+		return;
+	tty_port_shutdown(port, tty);
+	if (!port->console)
+		set_bit(TTY_IO_ERROR, &tty->flags);
+	tty_port_close_end(port, tty);
+	tty_port_tty_set(port, NULL);
+}
+EXPORT_SYMBOL(tty_port_close);
+
+/**
+ * tty_port_install - generic tty->ops->install handler
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @tty: tty to be installed
+ *
+ * It is the same as tty_standard_install() except the provided @port is linked
+ * to a concrete tty specified by @tty. Use this or tty_port_register_device()
+ * (or both). Call tty_port_link_device() as a last resort.
+ */
+int tty_port_install(struct tty_port *port, struct tty_driver *driver,
+		struct tty_struct *tty)
+{
+	tty->port = port;
+	return tty_standard_install(driver, tty);
+}
+EXPORT_SYMBOL_GPL(tty_port_install);
+
+/**
+ * tty_port_open - generic tty->ops->open handler
+ * @port: tty_port of the device
+ * @tty: tty to be opened
+ * @filp: passed file pointer
+ *
+ * It is a generic helper to be used in driver's @tty->ops->open. It activates
+ * the devices using @port->ops->activate if not active already. And waits for
+ * the device to be ready using tty_port_block_til_ready() (e.g.  raises
+ * DTR/CTS and waits for carrier).
+ *
+ * Note that @port->ops->shutdown is not called when @port->ops->activate
+ * returns an error (on the contrary, @tty->ops->close is).
+ *
+ * Locking: Caller holds tty lock.
+ *
+ * Note: may drop and reacquire tty lock (in tty_port_block_til_ready()) so
+ * @tty and @port may have changed state (eg., may be hung up now).
+ */
+int tty_port_open(struct tty_port *port, struct tty_struct *tty,
+							struct file *filp)
+{
+	spin_lock_irq(&port->lock);
+	++port->count;
+	spin_unlock_irq(&port->lock);
+	tty_port_tty_set(port, tty);
+
+	/*
+	 * Do the device-specific open only if the hardware isn't
+	 * already initialized. Serialize open and shutdown using the
+	 * port mutex.
+	 */
+
+	mutex_lock(&port->mutex);
+
+	if (!tty_port_initialized(port)) {
+		clear_bit(TTY_IO_ERROR, &tty->flags);
+		if (port->ops->activate) {
+			int retval = port->ops->activate(port, tty);
+
+			if (retval) {
+				mutex_unlock(&port->mutex);
+				return retval;
+			}
+		}
+		tty_port_set_initialized(port, 1);
+	}
+	mutex_unlock(&port->mutex);
+	return tty_port_block_til_ready(port, tty, filp);
+}
+EXPORT_SYMBOL(tty_port_open);