// 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 size_t tty_port_default_receive_buf(struct tty_port *port, const u8 *p,
const u8 *f, size_t count)
{
struct tty_struct *tty;
struct tty_ldisc *ld;
tty = READ_ONCE(port->itty);
if (!tty)
return 0;
ld = tty_ldisc_ref(tty);
if (!ld)
return 0;
count = tty_ldisc_receive_buf(ld, p, f, count);
tty_ldisc_deref(ld);
return count;
}
static void tty_port_default_lookahead_buf(struct tty_port *port, const u8 *p,
const u8 *f, size_t count)
{
struct tty_struct *tty;
struct tty_ldisc *ld;
tty = READ_ONCE(port->itty);
if (!tty)
return;
ld = tty_ldisc_ref(tty);
if (!ld)
return;
if (ld->ops->lookahead_buf)
ld->ops->lookahead_buf(ld->tty, p, f, count);
tty_ldisc_deref(ld);
}
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
* @host: serial port hardware device
* @parent: 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 *host, struct device *parent, void *drvdata,
const struct attribute_group **attr_grp)
{
struct device *dev;
tty_port_link_device(port, driver, index);
dev = serdev_tty_port_register(port, host, parent, 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, parent, 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
* @host: serial port hardware controller device
* @parent: 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 *host, struct device *parent)
{
return tty_port_register_device_attr_serdev(port, driver, index,
host, parent, 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 = (u8 *)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, false);
/*
* 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, false);
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.
*/
bool tty_port_carrier_raised(struct tty_port *port)
{
if (port->ops->carrier_raised == NULL)
return true;
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, true);
}
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, false);
}
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, true);
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, true);
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, true);
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, false);
}
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, true);
}
mutex_unlock(&port->mutex);
return tty_port_block_til_ready(port, tty, filp);
}
EXPORT_SYMBOL(tty_port_open);
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