1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_TTY_PORT_H
3 #define _LINUX_TTY_PORT_H
4 
5 #include <linux/kfifo.h>
6 #include <linux/kref.h>
7 #include <linux/mutex.h>
8 #include <linux/tty_buffer.h>
9 #include <linux/wait.h>
10 
11 struct attribute_group;
12 struct tty_driver;
13 struct tty_port;
14 struct tty_struct;
15 
16 /**
17  * struct tty_port_operations -- operations on tty_port
18  * @carrier_raised: return 1 if the carrier is raised on @port
19  * @dtr_rts: raise the DTR line if @raise is nonzero, otherwise lower DTR
20  * @shutdown: called when the last close completes or a hangup finishes IFF the
21  *	port was initialized. Do not use to free resources. Turn off the device
22  *	only. Called under the port mutex to serialize against @activate and
23  *	@shutdown.
24  * @activate: called under the port mutex from tty_port_open(), serialized using
25  *	the port mutex. Supposed to turn on the device.
26  *
27  *	FIXME: long term getting the tty argument *out* of this would be good
28  *	for consoles.
29  *
30  * @destruct: called on the final put of a port. Free resources, possibly incl.
31  *	the port itself.
32  */
33 struct tty_port_operations {
34 	int (*carrier_raised)(struct tty_port *port);
35 	void (*dtr_rts)(struct tty_port *port, int raise);
36 	void (*shutdown)(struct tty_port *port);
37 	int (*activate)(struct tty_port *port, struct tty_struct *tty);
38 	void (*destruct)(struct tty_port *port);
39 };
40 
41 struct tty_port_client_operations {
42 	int (*receive_buf)(struct tty_port *port, const unsigned char *, const unsigned char *, size_t);
43 	void (*write_wakeup)(struct tty_port *port);
44 };
45 
46 extern const struct tty_port_client_operations tty_port_default_client_ops;
47 
48 /**
49  * struct tty_port -- port level information
50  *
51  * @buf: buffer for this port, locked internally
52  * @tty: back pointer to &struct tty_struct, valid only if the tty is open. Use
53  *	 tty_port_tty_get() to obtain it (and tty_kref_put() to release).
54  * @itty: internal back pointer to &struct tty_struct. Avoid this. It should be
55  *	  eliminated in the long term.
56  * @ops: tty port operations (like activate, shutdown), see &struct
57  *	 tty_port_operations
58  * @client_ops: tty port client operations (like receive_buf, write_wakeup).
59  *		By default, tty_port_default_client_ops is used.
60  * @lock: lock protecting @tty
61  * @blocked_open: # of procs waiting for open in tty_port_block_til_ready()
62  * @count: usage count
63  * @open_wait: open waiters queue (waiting e.g. for a carrier)
64  * @delta_msr_wait: modem status change queue (waiting for MSR changes)
65  * @flags: user TTY flags (%ASYNC_)
66  * @iflags: internal flags (%TTY_PORT_)
67  * @console: when set, the port is a console
68  * @mutex: locking, for open, shutdown and other port operations
69  * @buf_mutex: @xmit_buf alloc lock
70  * @xmit_buf: optional xmit buffer used by some drivers
71  * @xmit_fifo: optional xmit buffer used by some drivers
72  * @close_delay: delay in jiffies to wait when closing the port
73  * @closing_wait: delay in jiffies for output to be sent before closing
74  * @drain_delay: set to zero if no pure time based drain is needed else set to
75  *		 size of fifo
76  * @kref: references counter. Reaching zero calls @ops->destruct() if non-%NULL
77  *	  or frees the port otherwise.
78  * @client_data: pointer to private data, for @client_ops
79  *
80  * Each device keeps its own port level information. &struct tty_port was
81  * introduced as a common structure for such information. As every TTY device
82  * shall have a backing tty_port structure, every driver can use these members.
83  *
84  * The tty port has a different lifetime to the tty so must be kept apart.
85  * In addition be careful as tty -> port mappings are valid for the life
86  * of the tty object but in many cases port -> tty mappings are valid only
87  * until a hangup so don't use the wrong path.
88  *
89  * Tty port shall be initialized by tty_port_init() and shut down either by
90  * tty_port_destroy() (refcounting not used), or tty_port_put() (refcounting).
91  *
92  * There is a lot of helpers around &struct tty_port too. To name the most
93  * significant ones: tty_port_open(), tty_port_close() (or
94  * tty_port_close_start() and tty_port_close_end() separately if need be), and
95  * tty_port_hangup(). These call @ops->activate() and @ops->shutdown() as
96  * needed.
97  */
98 struct tty_port {
99 	struct tty_bufhead	buf;
100 	struct tty_struct	*tty;
101 	struct tty_struct	*itty;
102 	const struct tty_port_operations *ops;
103 	const struct tty_port_client_operations *client_ops;
104 	spinlock_t		lock;
105 	int			blocked_open;
106 	int			count;
107 	wait_queue_head_t	open_wait;
108 	wait_queue_head_t	delta_msr_wait;
109 	unsigned long		flags;
110 	unsigned long		iflags;
111 	unsigned char		console:1;
112 	struct mutex		mutex;
113 	struct mutex		buf_mutex;
114 	unsigned char		*xmit_buf;
115 	DECLARE_KFIFO_PTR(xmit_fifo, unsigned char);
116 	unsigned int		close_delay;
117 	unsigned int		closing_wait;
118 	int			drain_delay;
119 	struct kref		kref;
120 	void			*client_data;
121 };
122 
123 /* tty_port::iflags bits -- use atomic bit ops */
124 #define TTY_PORT_INITIALIZED	0	/* device is initialized */
125 #define TTY_PORT_SUSPENDED	1	/* device is suspended */
126 #define TTY_PORT_ACTIVE		2	/* device is open */
127 
128 /*
129  * uart drivers: use the uart_port::status field and the UPSTAT_* defines
130  * for s/w-based flow control steering and carrier detection status
131  */
132 #define TTY_PORT_CTS_FLOW	3	/* h/w flow control enabled */
133 #define TTY_PORT_CHECK_CD	4	/* carrier detect enabled */
134 #define TTY_PORT_KOPENED	5	/* device exclusively opened by
135 					   kernel */
136 
137 void tty_port_init(struct tty_port *port);
138 void tty_port_link_device(struct tty_port *port, struct tty_driver *driver,
139 		unsigned index);
140 struct device *tty_port_register_device(struct tty_port *port,
141 		struct tty_driver *driver, unsigned index,
142 		struct device *device);
143 struct device *tty_port_register_device_attr(struct tty_port *port,
144 		struct tty_driver *driver, unsigned index,
145 		struct device *device, void *drvdata,
146 		const struct attribute_group **attr_grp);
147 struct device *tty_port_register_device_serdev(struct tty_port *port,
148 		struct tty_driver *driver, unsigned index,
149 		struct device *device);
150 struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
151 		struct tty_driver *driver, unsigned index,
152 		struct device *device, void *drvdata,
153 		const struct attribute_group **attr_grp);
154 void tty_port_unregister_device(struct tty_port *port,
155 		struct tty_driver *driver, unsigned index);
156 int tty_port_alloc_xmit_buf(struct tty_port *port);
157 void tty_port_free_xmit_buf(struct tty_port *port);
158 void tty_port_destroy(struct tty_port *port);
159 void tty_port_put(struct tty_port *port);
160 
tty_port_get(struct tty_port * port)161 static inline struct tty_port *tty_port_get(struct tty_port *port)
162 {
163 	if (port && kref_get_unless_zero(&port->kref))
164 		return port;
165 	return NULL;
166 }
167 
168 /* If the cts flow control is enabled, return true. */
tty_port_cts_enabled(const struct tty_port * port)169 static inline bool tty_port_cts_enabled(const struct tty_port *port)
170 {
171 	return test_bit(TTY_PORT_CTS_FLOW, &port->iflags);
172 }
173 
tty_port_set_cts_flow(struct tty_port * port,bool val)174 static inline void tty_port_set_cts_flow(struct tty_port *port, bool val)
175 {
176 	assign_bit(TTY_PORT_CTS_FLOW, &port->iflags, val);
177 }
178 
tty_port_active(const struct tty_port * port)179 static inline bool tty_port_active(const struct tty_port *port)
180 {
181 	return test_bit(TTY_PORT_ACTIVE, &port->iflags);
182 }
183 
tty_port_set_active(struct tty_port * port,bool val)184 static inline void tty_port_set_active(struct tty_port *port, bool val)
185 {
186 	assign_bit(TTY_PORT_ACTIVE, &port->iflags, val);
187 }
188 
tty_port_check_carrier(const struct tty_port * port)189 static inline bool tty_port_check_carrier(const struct tty_port *port)
190 {
191 	return test_bit(TTY_PORT_CHECK_CD, &port->iflags);
192 }
193 
tty_port_set_check_carrier(struct tty_port * port,bool val)194 static inline void tty_port_set_check_carrier(struct tty_port *port, bool val)
195 {
196 	assign_bit(TTY_PORT_CHECK_CD, &port->iflags, val);
197 }
198 
tty_port_suspended(const struct tty_port * port)199 static inline bool tty_port_suspended(const struct tty_port *port)
200 {
201 	return test_bit(TTY_PORT_SUSPENDED, &port->iflags);
202 }
203 
tty_port_set_suspended(struct tty_port * port,bool val)204 static inline void tty_port_set_suspended(struct tty_port *port, bool val)
205 {
206 	assign_bit(TTY_PORT_SUSPENDED, &port->iflags, val);
207 }
208 
tty_port_initialized(const struct tty_port * port)209 static inline bool tty_port_initialized(const struct tty_port *port)
210 {
211 	return test_bit(TTY_PORT_INITIALIZED, &port->iflags);
212 }
213 
tty_port_set_initialized(struct tty_port * port,bool val)214 static inline void tty_port_set_initialized(struct tty_port *port, bool val)
215 {
216 	assign_bit(TTY_PORT_INITIALIZED, &port->iflags, val);
217 }
218 
tty_port_kopened(const struct tty_port * port)219 static inline bool tty_port_kopened(const struct tty_port *port)
220 {
221 	return test_bit(TTY_PORT_KOPENED, &port->iflags);
222 }
223 
tty_port_set_kopened(struct tty_port * port,bool val)224 static inline void tty_port_set_kopened(struct tty_port *port, bool val)
225 {
226 	assign_bit(TTY_PORT_KOPENED, &port->iflags, val);
227 }
228 
229 struct tty_struct *tty_port_tty_get(struct tty_port *port);
230 void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
231 int tty_port_carrier_raised(struct tty_port *port);
232 void tty_port_raise_dtr_rts(struct tty_port *port);
233 void tty_port_lower_dtr_rts(struct tty_port *port);
234 void tty_port_hangup(struct tty_port *port);
235 void tty_port_tty_hangup(struct tty_port *port, bool check_clocal);
236 void tty_port_tty_wakeup(struct tty_port *port);
237 int tty_port_block_til_ready(struct tty_port *port, struct tty_struct *tty,
238 		struct file *filp);
239 int tty_port_close_start(struct tty_port *port, struct tty_struct *tty,
240 		struct file *filp);
241 void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
242 void tty_port_close(struct tty_port *port, struct tty_struct *tty,
243 		struct file *filp);
244 int tty_port_install(struct tty_port *port, struct tty_driver *driver,
245 		struct tty_struct *tty);
246 int tty_port_open(struct tty_port *port, struct tty_struct *tty,
247 		struct file *filp);
248 
tty_port_users(struct tty_port * port)249 static inline int tty_port_users(struct tty_port *port)
250 {
251 	return port->count + port->blocked_open;
252 }
253 
254 #endif
255