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