2021-07-23 10:31:46 +00:00
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_TTY_PORT_H
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#define _LINUX_TTY_PORT_H
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2022-01-24 07:14:22 +00:00
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#include <linux/kfifo.h>
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2021-07-23 10:31:46 +00:00
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#include <linux/kref.h>
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#include <linux/mutex.h>
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#include <linux/tty_buffer.h>
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#include <linux/wait.h>
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struct attribute_group;
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struct tty_driver;
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struct tty_port;
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struct tty_struct;
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2021-11-26 08:15:53 +00:00
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/**
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* struct tty_port_operations -- operations on tty_port
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* @carrier_raised: return 1 if the carrier is raised on @port
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* @dtr_rts: raise the DTR line if @raise is nonzero, otherwise lower DTR
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* @shutdown: called when the last close completes or a hangup finishes IFF the
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* port was initialized. Do not use to free resources. Turn off the device
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* only. Called under the port mutex to serialize against @activate and
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* @shutdown.
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* @activate: called under the port mutex from tty_port_open(), serialized using
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* the port mutex. Supposed to turn on the device.
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*
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* FIXME: long term getting the tty argument *out* of this would be good
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* for consoles.
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*
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* @destruct: called on the final put of a port. Free resources, possibly incl.
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* the port itself.
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*/
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2021-07-23 10:31:46 +00:00
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struct tty_port_operations {
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int (*carrier_raised)(struct tty_port *port);
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void (*dtr_rts)(struct tty_port *port, int raise);
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void (*shutdown)(struct tty_port *port);
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int (*activate)(struct tty_port *port, struct tty_struct *tty);
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void (*destruct)(struct tty_port *port);
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};
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struct tty_port_client_operations {
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int (*receive_buf)(struct tty_port *port, const unsigned char *, const unsigned char *, size_t);
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tty: Implement lookahead to process XON/XOFF timely
When tty is not read from, XON/XOFF may get stuck into an
intermediate buffer. As those characters are there to do software
flow-control, it is not very useful. In the case where neither end
reads from ttys, the receiving ends might not be able receive the
XOFF characters and just keep sending more data to the opposite
direction. This problem is almost guaranteed to occur with DMA
which sends data in large chunks.
If TTY is slow to process characters, that is, eats less than given
amount in receive_buf, invoke lookahead for the rest of the chars
to process potential XON/XOFF characters.
We need to keep track of how many characters have been processed by the
lookahead to avoid processing the flow control char again on the normal
path. Bookkeeping occurs parallel on two layers (tty_buffer and n_tty)
to avoid passing the lookahead_count through the whole call chain.
When a flow-control char is processed, two things must occur:
a) it must not be treated as normal char
b) if not yet processed, flow-control actions need to be taken
The return value of n_tty_receive_char_flow_ctrl() tells caller a), and
b) is kept internal to n_tty_receive_char_flow_ctrl().
If characters were previous looked ahead, __receive_buf() makes two
calls to the appropriate n_tty_receive_buf_* function. First call is
made with lookahead_done=true for the characters that were subject to
lookahead earlier and then with lookahead=false for the new characters.
Either of the calls might be skipped when it has no characters to
handle.
Reported-by: Gilles Buloz <gilles.buloz@kontron.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220606153652.63554-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-06-06 15:36:51 +00:00
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void (*lookahead_buf)(struct tty_port *port, const unsigned char *cp,
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const unsigned char *fp, unsigned int count);
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2021-07-23 10:31:46 +00:00
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void (*write_wakeup)(struct tty_port *port);
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};
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extern const struct tty_port_client_operations tty_port_default_client_ops;
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2021-11-26 08:15:50 +00:00
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/**
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* struct tty_port -- port level information
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*
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* @buf: buffer for this port, locked internally
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* @tty: back pointer to &struct tty_struct, valid only if the tty is open. Use
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* tty_port_tty_get() to obtain it (and tty_kref_put() to release).
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* @itty: internal back pointer to &struct tty_struct. Avoid this. It should be
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* eliminated in the long term.
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* @ops: tty port operations (like activate, shutdown), see &struct
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* tty_port_operations
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* @client_ops: tty port client operations (like receive_buf, write_wakeup).
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* By default, tty_port_default_client_ops is used.
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* @lock: lock protecting @tty
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* @blocked_open: # of procs waiting for open in tty_port_block_til_ready()
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* @count: usage count
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* @open_wait: open waiters queue (waiting e.g. for a carrier)
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* @delta_msr_wait: modem status change queue (waiting for MSR changes)
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* @flags: user TTY flags (%ASYNC_)
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* @iflags: internal flags (%TTY_PORT_)
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* @console: when set, the port is a console
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* @mutex: locking, for open, shutdown and other port operations
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* @buf_mutex: @xmit_buf alloc lock
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* @xmit_buf: optional xmit buffer used by some drivers
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2022-01-24 07:14:22 +00:00
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* @xmit_fifo: optional xmit buffer used by some drivers
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2021-11-26 08:15:50 +00:00
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* @close_delay: delay in jiffies to wait when closing the port
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* @closing_wait: delay in jiffies for output to be sent before closing
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* @drain_delay: set to zero if no pure time based drain is needed else set to
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* size of fifo
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* @kref: references counter. Reaching zero calls @ops->destruct() if non-%NULL
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* or frees the port otherwise.
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* @client_data: pointer to private data, for @client_ops
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*
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* Each device keeps its own port level information. &struct tty_port was
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* introduced as a common structure for such information. As every TTY device
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* shall have a backing tty_port structure, every driver can use these members.
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*
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* The tty port has a different lifetime to the tty so must be kept apart.
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* In addition be careful as tty -> port mappings are valid for the life
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* of the tty object but in many cases port -> tty mappings are valid only
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* until a hangup so don't use the wrong path.
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*
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* Tty port shall be initialized by tty_port_init() and shut down either by
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* tty_port_destroy() (refcounting not used), or tty_port_put() (refcounting).
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*
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* There is a lot of helpers around &struct tty_port too. To name the most
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* significant ones: tty_port_open(), tty_port_close() (or
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* tty_port_close_start() and tty_port_close_end() separately if need be), and
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* tty_port_hangup(). These call @ops->activate() and @ops->shutdown() as
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* needed.
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*/
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2021-07-23 10:31:46 +00:00
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struct tty_port {
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2021-11-26 08:15:50 +00:00
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struct tty_bufhead buf;
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struct tty_struct *tty;
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struct tty_struct *itty;
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const struct tty_port_operations *ops;
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const struct tty_port_client_operations *client_ops;
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spinlock_t lock;
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int blocked_open;
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int count;
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wait_queue_head_t open_wait;
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wait_queue_head_t delta_msr_wait;
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unsigned long flags;
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unsigned long iflags;
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unsigned char console:1;
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struct mutex mutex;
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struct mutex buf_mutex;
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unsigned char *xmit_buf;
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2022-01-24 07:14:22 +00:00
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DECLARE_KFIFO_PTR(xmit_fifo, unsigned char);
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2021-11-26 08:15:50 +00:00
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unsigned int close_delay;
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unsigned int closing_wait;
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int drain_delay;
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struct kref kref;
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void *client_data;
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2021-07-23 10:31:46 +00:00
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};
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/* tty_port::iflags bits -- use atomic bit ops */
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#define TTY_PORT_INITIALIZED 0 /* device is initialized */
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#define TTY_PORT_SUSPENDED 1 /* device is suspended */
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#define TTY_PORT_ACTIVE 2 /* device is open */
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/*
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* uart drivers: use the uart_port::status field and the UPSTAT_* defines
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* for s/w-based flow control steering and carrier detection status
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*/
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#define TTY_PORT_CTS_FLOW 3 /* h/w flow control enabled */
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#define TTY_PORT_CHECK_CD 4 /* carrier detect enabled */
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#define TTY_PORT_KOPENED 5 /* device exclusively opened by
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kernel */
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void tty_port_init(struct tty_port *port);
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void tty_port_link_device(struct tty_port *port, struct tty_driver *driver,
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unsigned index);
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struct device *tty_port_register_device(struct tty_port *port,
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struct tty_driver *driver, unsigned index,
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struct device *device);
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struct device *tty_port_register_device_attr(struct tty_port *port,
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struct tty_driver *driver, unsigned index,
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struct device *device, void *drvdata,
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const struct attribute_group **attr_grp);
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struct device *tty_port_register_device_serdev(struct tty_port *port,
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struct tty_driver *driver, unsigned index,
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struct device *device);
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struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
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struct tty_driver *driver, unsigned index,
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struct device *device, void *drvdata,
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const struct attribute_group **attr_grp);
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void tty_port_unregister_device(struct tty_port *port,
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struct tty_driver *driver, unsigned index);
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int tty_port_alloc_xmit_buf(struct tty_port *port);
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void tty_port_free_xmit_buf(struct tty_port *port);
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void tty_port_destroy(struct tty_port *port);
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void tty_port_put(struct tty_port *port);
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static inline struct tty_port *tty_port_get(struct tty_port *port)
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{
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if (port && kref_get_unless_zero(&port->kref))
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return port;
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return NULL;
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}
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/* If the cts flow control is enabled, return true. */
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static inline bool tty_port_cts_enabled(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_CTS_FLOW, &port->iflags);
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}
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static inline void tty_port_set_cts_flow(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_CTS_FLOW, &port->iflags, val);
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}
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static inline bool tty_port_active(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_ACTIVE, &port->iflags);
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}
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static inline void tty_port_set_active(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_ACTIVE, &port->iflags, val);
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}
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static inline bool tty_port_check_carrier(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_CHECK_CD, &port->iflags);
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}
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static inline void tty_port_set_check_carrier(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_CHECK_CD, &port->iflags, val);
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}
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static inline bool tty_port_suspended(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_SUSPENDED, &port->iflags);
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}
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static inline void tty_port_set_suspended(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_SUSPENDED, &port->iflags, val);
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}
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static inline bool tty_port_initialized(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_INITIALIZED, &port->iflags);
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}
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static inline void tty_port_set_initialized(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_INITIALIZED, &port->iflags, val);
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}
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static inline bool tty_port_kopened(const struct tty_port *port)
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{
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return test_bit(TTY_PORT_KOPENED, &port->iflags);
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}
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static inline void tty_port_set_kopened(struct tty_port *port, bool val)
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{
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assign_bit(TTY_PORT_KOPENED, &port->iflags, val);
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}
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struct tty_struct *tty_port_tty_get(struct tty_port *port);
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void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
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int tty_port_carrier_raised(struct tty_port *port);
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void tty_port_raise_dtr_rts(struct tty_port *port);
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void tty_port_lower_dtr_rts(struct tty_port *port);
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void tty_port_hangup(struct tty_port *port);
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void tty_port_tty_hangup(struct tty_port *port, bool check_clocal);
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void tty_port_tty_wakeup(struct tty_port *port);
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int tty_port_block_til_ready(struct tty_port *port, struct tty_struct *tty,
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struct file *filp);
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int tty_port_close_start(struct tty_port *port, struct tty_struct *tty,
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struct file *filp);
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void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
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void tty_port_close(struct tty_port *port, struct tty_struct *tty,
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struct file *filp);
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int tty_port_install(struct tty_port *port, struct tty_driver *driver,
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struct tty_struct *tty);
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int tty_port_open(struct tty_port *port, struct tty_struct *tty,
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struct file *filp);
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static inline int tty_port_users(struct tty_port *port)
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{
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return port->count + port->blocked_open;
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}
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#endif
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