1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _LINUX_TTY_LDISC_H |
3 | #define _LINUX_TTY_LDISC_H |
4 | |
5 | struct tty_struct; |
6 | |
7 | #include <linux/fs.h> |
8 | #include <linux/wait.h> |
9 | #include <linux/atomic.h> |
10 | #include <linux/list.h> |
11 | #include <linux/lockdep.h> |
12 | #include <linux/seq_file.h> |
13 | |
14 | /* |
15 | * the semaphore definition |
16 | */ |
17 | struct ld_semaphore { |
18 | atomic_long_t count; |
19 | raw_spinlock_t wait_lock; |
20 | unsigned int wait_readers; |
21 | struct list_head read_wait; |
22 | struct list_head write_wait; |
23 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
24 | struct lockdep_map dep_map; |
25 | #endif |
26 | }; |
27 | |
28 | void __init_ldsem(struct ld_semaphore *sem, const char *name, |
29 | struct lock_class_key *key); |
30 | |
31 | #define init_ldsem(sem) \ |
32 | do { \ |
33 | static struct lock_class_key __key; \ |
34 | \ |
35 | __init_ldsem((sem), #sem, &__key); \ |
36 | } while (0) |
37 | |
38 | |
39 | int ldsem_down_read(struct ld_semaphore *sem, long timeout); |
40 | int ldsem_down_read_trylock(struct ld_semaphore *sem); |
41 | int ldsem_down_write(struct ld_semaphore *sem, long timeout); |
42 | int ldsem_down_write_trylock(struct ld_semaphore *sem); |
43 | void ldsem_up_read(struct ld_semaphore *sem); |
44 | void ldsem_up_write(struct ld_semaphore *sem); |
45 | |
46 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
47 | int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass, |
48 | long timeout); |
49 | int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, |
50 | long timeout); |
51 | #else |
52 | # define ldsem_down_read_nested(sem, subclass, timeout) \ |
53 | ldsem_down_read(sem, timeout) |
54 | # define ldsem_down_write_nested(sem, subclass, timeout) \ |
55 | ldsem_down_write(sem, timeout) |
56 | #endif |
57 | |
58 | /** |
59 | * struct tty_ldisc_ops - ldisc operations |
60 | * |
61 | * @name: name of this ldisc rendered in /proc/tty/ldiscs |
62 | * @num: ``N_*`` number (%N_TTY, %N_HDLC, ...) reserved to this ldisc |
63 | * |
64 | * @open: [TTY] ``int ()(struct tty_struct *tty)`` |
65 | * |
66 | * This function is called when the line discipline is associated with the |
67 | * @tty. No other call into the line discipline for this tty will occur |
68 | * until it completes successfully. It should initialize any state needed |
69 | * by the ldisc, and set @tty->receive_room to the maximum amount of data |
70 | * the line discipline is willing to accept from the driver with a single |
71 | * call to @receive_buf(). Returning an error will prevent the ldisc from |
72 | * being attached. |
73 | * |
74 | * Optional. Can sleep. |
75 | * |
76 | * @close: [TTY] ``void ()(struct tty_struct *tty)`` |
77 | * |
78 | * This function is called when the line discipline is being shutdown, |
79 | * either because the @tty is being closed or because the @tty is being |
80 | * changed to use a new line discipline. At the point of execution no |
81 | * further users will enter the ldisc code for this tty. |
82 | * |
83 | * Optional. Can sleep. |
84 | * |
85 | * @flush_buffer: [TTY] ``void ()(struct tty_struct *tty)`` |
86 | * |
87 | * This function instructs the line discipline to clear its buffers of any |
88 | * input characters it may have queued to be delivered to the user mode |
89 | * process. It may be called at any point between open and close. |
90 | * |
91 | * Optional. |
92 | * |
93 | * @read: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file, u8 *buf, |
94 | * size_t nr)`` |
95 | * |
96 | * This function is called when the user requests to read from the @tty. |
97 | * The line discipline will return whatever characters it has buffered up |
98 | * for the user. If this function is not defined, the user will receive |
99 | * an %EIO error. Multiple read calls may occur in parallel and the ldisc |
100 | * must deal with serialization issues. |
101 | * |
102 | * Optional: %EIO unless provided. Can sleep. |
103 | * |
104 | * @write: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file, |
105 | * const u8 *buf, size_t nr)`` |
106 | * |
107 | * This function is called when the user requests to write to the @tty. |
108 | * The line discipline will deliver the characters to the low-level tty |
109 | * device for transmission, optionally performing some processing on the |
110 | * characters first. If this function is not defined, the user will |
111 | * receive an %EIO error. |
112 | * |
113 | * Optional: %EIO unless provided. Can sleep. |
114 | * |
115 | * @ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, |
116 | * unsigned long arg)`` |
117 | * |
118 | * This function is called when the user requests an ioctl which is not |
119 | * handled by the tty layer or the low-level tty driver. It is intended |
120 | * for ioctls which affect line discpline operation. Note that the search |
121 | * order for ioctls is (1) tty layer, (2) tty low-level driver, (3) line |
122 | * discpline. So a low-level driver can "grab" an ioctl request before |
123 | * the line discpline has a chance to see it. |
124 | * |
125 | * Optional. |
126 | * |
127 | * @compat_ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, |
128 | * unsigned long arg)`` |
129 | * |
130 | * Process ioctl calls from 32-bit process on 64-bit system. |
131 | * |
132 | * Note that only ioctls that are neither "pointer to compatible |
133 | * structure" nor tty-generic. Something private that takes an integer or |
134 | * a pointer to wordsize-sensitive structure belongs here, but most of |
135 | * ldiscs will happily leave it %NULL. |
136 | * |
137 | * Optional. |
138 | * |
139 | * @set_termios: [TTY] ``void ()(struct tty_struct *tty, const struct ktermios *old)`` |
140 | * |
141 | * This function notifies the line discpline that a change has been made |
142 | * to the termios structure. |
143 | * |
144 | * Optional. |
145 | * |
146 | * @poll: [TTY] ``int ()(struct tty_struct *tty, struct file *file, |
147 | * struct poll_table_struct *wait)`` |
148 | * |
149 | * This function is called when a user attempts to select/poll on a @tty |
150 | * device. It is solely the responsibility of the line discipline to |
151 | * handle poll requests. |
152 | * |
153 | * Optional. |
154 | * |
155 | * @hangup: [TTY] ``void ()(struct tty_struct *tty)`` |
156 | * |
157 | * Called on a hangup. Tells the discipline that it should cease I/O to |
158 | * the tty driver. The driver should seek to perform this action quickly |
159 | * but should wait until any pending driver I/O is completed. No further |
160 | * calls into the ldisc code will occur. |
161 | * |
162 | * Optional. Can sleep. |
163 | * |
164 | * @receive_buf: [DRV] ``void ()(struct tty_struct *tty, const u8 *cp, |
165 | * const u8 *fp, size_t count)`` |
166 | * |
167 | * This function is called by the low-level tty driver to send characters |
168 | * received by the hardware to the line discpline for processing. @cp is |
169 | * a pointer to the buffer of input character received by the device. @fp |
170 | * is a pointer to an array of flag bytes which indicate whether a |
171 | * character was received with a parity error, etc. @fp may be %NULL to |
172 | * indicate all data received is %TTY_NORMAL. |
173 | * |
174 | * Optional. |
175 | * |
176 | * @write_wakeup: [DRV] ``void ()(struct tty_struct *tty)`` |
177 | * |
178 | * This function is called by the low-level tty driver to signal that line |
179 | * discpline should try to send more characters to the low-level driver |
180 | * for transmission. If the line discpline does not have any more data to |
181 | * send, it can just return. If the line discipline does have some data to |
182 | * send, please arise a tasklet or workqueue to do the real data transfer. |
183 | * Do not send data in this hook, it may lead to a deadlock. |
184 | * |
185 | * Optional. |
186 | * |
187 | * @dcd_change: [DRV] ``void ()(struct tty_struct *tty, bool active)`` |
188 | * |
189 | * Tells the discipline that the DCD pin has changed its status. Used |
190 | * exclusively by the %N_PPS (Pulse-Per-Second) line discipline. |
191 | * |
192 | * Optional. |
193 | * |
194 | * @receive_buf2: [DRV] ``ssize_t ()(struct tty_struct *tty, const u8 *cp, |
195 | * const u8 *fp, size_t count)`` |
196 | * |
197 | * This function is called by the low-level tty driver to send characters |
198 | * received by the hardware to the line discpline for processing. @cp is a |
199 | * pointer to the buffer of input character received by the device. @fp |
200 | * is a pointer to an array of flag bytes which indicate whether a |
201 | * character was received with a parity error, etc. @fp may be %NULL to |
202 | * indicate all data received is %TTY_NORMAL. If assigned, prefer this |
203 | * function for automatic flow control. |
204 | * |
205 | * Optional. |
206 | * |
207 | * @lookahead_buf: [DRV] ``void ()(struct tty_struct *tty, const u8 *cp, |
208 | * const u8 *fp, size_t count)`` |
209 | * |
210 | * This function is called by the low-level tty driver for characters |
211 | * not eaten by ->receive_buf() or ->receive_buf2(). It is useful for |
212 | * processing high-priority characters such as software flow-control |
213 | * characters that could otherwise get stuck into the intermediate |
214 | * buffer until tty has room to receive them. Ldisc must be able to |
215 | * handle later a ->receive_buf() or ->receive_buf2() call for the |
216 | * same characters (e.g. by skipping the actions for high-priority |
217 | * characters already handled by ->lookahead_buf()). |
218 | * |
219 | * Optional. |
220 | * |
221 | * @owner: module containting this ldisc (for reference counting) |
222 | * |
223 | * This structure defines the interface between the tty line discipline |
224 | * implementation and the tty routines. The above routines can be defined. |
225 | * Unless noted otherwise, they are optional, and can be filled in with a %NULL |
226 | * pointer. |
227 | * |
228 | * Hooks marked [TTY] are invoked from the TTY core, the [DRV] ones from the |
229 | * tty_driver side. |
230 | */ |
231 | struct tty_ldisc_ops { |
232 | char *name; |
233 | int num; |
234 | |
235 | /* |
236 | * The following routines are called from above. |
237 | */ |
238 | int (*open)(struct tty_struct *tty); |
239 | void (*close)(struct tty_struct *tty); |
240 | void (*flush_buffer)(struct tty_struct *tty); |
241 | ssize_t (*read)(struct tty_struct *tty, struct file *file, u8 *buf, |
242 | size_t nr, void **cookie, unsigned long offset); |
243 | ssize_t (*write)(struct tty_struct *tty, struct file *file, |
244 | const u8 *buf, size_t nr); |
245 | int (*ioctl)(struct tty_struct *tty, unsigned int cmd, |
246 | unsigned long arg); |
247 | int (*compat_ioctl)(struct tty_struct *tty, unsigned int cmd, |
248 | unsigned long arg); |
249 | void (*set_termios)(struct tty_struct *tty, const struct ktermios *old); |
250 | __poll_t (*poll)(struct tty_struct *tty, struct file *file, |
251 | struct poll_table_struct *wait); |
252 | void (*hangup)(struct tty_struct *tty); |
253 | |
254 | /* |
255 | * The following routines are called from below. |
256 | */ |
257 | void (*receive_buf)(struct tty_struct *tty, const u8 *cp, |
258 | const u8 *fp, size_t count); |
259 | void (*write_wakeup)(struct tty_struct *tty); |
260 | void (*dcd_change)(struct tty_struct *tty, bool active); |
261 | size_t (*receive_buf2)(struct tty_struct *tty, const u8 *cp, |
262 | const u8 *fp, size_t count); |
263 | void (*lookahead_buf)(struct tty_struct *tty, const u8 *cp, |
264 | const u8 *fp, size_t count); |
265 | |
266 | struct module *owner; |
267 | }; |
268 | |
269 | struct tty_ldisc { |
270 | struct tty_ldisc_ops *ops; |
271 | struct tty_struct *tty; |
272 | }; |
273 | |
274 | #define MODULE_ALIAS_LDISC(ldisc) \ |
275 | MODULE_ALIAS("tty-ldisc-" __stringify(ldisc)) |
276 | |
277 | extern const struct seq_operations tty_ldiscs_seq_ops; |
278 | |
279 | struct tty_ldisc *tty_ldisc_ref(struct tty_struct *); |
280 | void tty_ldisc_deref(struct tty_ldisc *); |
281 | struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *); |
282 | |
283 | void tty_ldisc_flush(struct tty_struct *tty); |
284 | |
285 | int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc); |
286 | void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc); |
287 | int tty_set_ldisc(struct tty_struct *tty, int disc); |
288 | |
289 | #endif /* _LINUX_TTY_LDISC_H */ |
290 | |