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 * 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 * 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 * @read: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file, 92 * unsigned char *buf, size_t nr)`` 93 * 94 * This function is called when the user requests to read from the @tty. 95 * The line discipline will return whatever characters it has buffered up 96 * for the user. If this function is not defined, the user will receive 97 * an %EIO error. Multiple read calls may occur in parallel and the ldisc 98 * must deal with serialization issues. 99 * 100 * Can sleep. 101 * 102 * @write: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file, 103 * const unsigned char *buf, size_t nr)`` 104 * 105 * This function is called when the user requests to write to the @tty. 106 * The line discipline will deliver the characters to the low-level tty 107 * device for transmission, optionally performing some processing on the 108 * characters first. If this function is not defined, the user will 109 * receive an %EIO error. 110 * 111 * Can sleep. 112 * 113 * @ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, 114 * unsigned long arg)`` 115 * 116 * This function is called when the user requests an ioctl which is not 117 * handled by the tty layer or the low-level tty driver. It is intended 118 * for ioctls which affect line discpline operation. Note that the search 119 * order for ioctls is (1) tty layer, (2) tty low-level driver, (3) line 120 * discpline. So a low-level driver can "grab" an ioctl request before 121 * the line discpline has a chance to see it. 122 * 123 * @compat_ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd, 124 * unsigned long arg)`` 125 * 126 * Process ioctl calls from 32-bit process on 64-bit system. 127 * 128 * Note that only ioctls that are neither "pointer to compatible 129 * structure" nor tty-generic. Something private that takes an integer or 130 * a pointer to wordsize-sensitive structure belongs here, but most of 131 * ldiscs will happily leave it %NULL. 132 * 133 * @set_termios: [TTY] ``void ()(struct tty_struct *tty, const struct ktermios *old)`` 134 * 135 * This function notifies the line discpline that a change has been made 136 * to the termios structure. 137 * 138 * @poll: [TTY] ``int ()(struct tty_struct *tty, struct file *file, 139 * struct poll_table_struct *wait)`` 140 * 141 * This function is called when a user attempts to select/poll on a @tty 142 * device. It is solely the responsibility of the line discipline to 143 * handle poll requests. 144 * 145 * @hangup: [TTY] ``void ()(struct tty_struct *tty)`` 146 * 147 * Called on a hangup. Tells the discipline that it should cease I/O to 148 * the tty driver. The driver should seek to perform this action quickly 149 * but should wait until any pending driver I/O is completed. No further 150 * calls into the ldisc code will occur. 151 * 152 * Can sleep. 153 * 154 * @receive_buf: [DRV] ``void ()(struct tty_struct *tty, 155 * const unsigned char *cp, const char *fp, int count)`` 156 * 157 * This function is called by the low-level tty driver to send characters 158 * received by the hardware to the line discpline for processing. @cp is 159 * a pointer to the buffer of input character received by the device. @fp 160 * is a pointer to an array of flag bytes which indicate whether a 161 * character was received with a parity error, etc. @fp may be %NULL to 162 * indicate all data received is %TTY_NORMAL. 163 * 164 * @write_wakeup: [DRV] ``void ()(struct tty_struct *tty)`` 165 * 166 * This function is called by the low-level tty driver to signal that line 167 * discpline should try to send more characters to the low-level driver 168 * for transmission. If the line discpline does not have any more data to 169 * send, it can just return. If the line discipline does have some data to 170 * send, please arise a tasklet or workqueue to do the real data transfer. 171 * Do not send data in this hook, it may lead to a deadlock. 172 * 173 * @dcd_change: [DRV] ``void ()(struct tty_struct *tty, bool active)`` 174 * 175 * Tells the discipline that the DCD pin has changed its status. Used 176 * exclusively by the %N_PPS (Pulse-Per-Second) line discipline. 177 * 178 * @receive_buf2: [DRV] ``int ()(struct tty_struct *tty, 179 * const unsigned char *cp, const char *fp, int count)`` 180 * 181 * This function is called by the low-level tty driver to send characters 182 * received by the hardware to the line discpline for processing. @cp is a 183 * pointer to the buffer of input character received by the device. @fp 184 * is a pointer to an array of flag bytes which indicate whether a 185 * character was received with a parity error, etc. @fp may be %NULL to 186 * indicate all data received is %TTY_NORMAL. If assigned, prefer this 187 * function for automatic flow control. 188 * 189 * @lookahead_buf: [DRV] ``void ()(struct tty_struct *tty, 190 * const unsigned char *cp, const char *fp, int count)`` 191 * 192 * This function is called by the low-level tty driver for characters 193 * not eaten by ->receive_buf() or ->receive_buf2(). It is useful for 194 * processing high-priority characters such as software flow-control 195 * characters that could otherwise get stuck into the intermediate 196 * buffer until tty has room to receive them. Ldisc must be able to 197 * handle later a ->receive_buf() or ->receive_buf2() call for the 198 * same characters (e.g. by skipping the actions for high-priority 199 * characters already handled by ->lookahead_buf()). 200 * 201 * @owner: module containting this ldisc (for reference counting) 202 * 203 * This structure defines the interface between the tty line discipline 204 * implementation and the tty routines. The above routines can be defined. 205 * Unless noted otherwise, they are optional, and can be filled in with a %NULL 206 * pointer. 207 * 208 * Hooks marked [TTY] are invoked from the TTY core, the [DRV] ones from the 209 * tty_driver side. 210 */ 211 struct tty_ldisc_ops { 212 char *name; 213 int num; 214 215 /* 216 * The following routines are called from above. 217 */ 218 int (*open)(struct tty_struct *tty); 219 void (*close)(struct tty_struct *tty); 220 void (*flush_buffer)(struct tty_struct *tty); 221 ssize_t (*read)(struct tty_struct *tty, struct file *file, 222 unsigned char *buf, size_t nr, 223 void **cookie, unsigned long offset); 224 ssize_t (*write)(struct tty_struct *tty, struct file *file, 225 const unsigned char *buf, size_t nr); 226 int (*ioctl)(struct tty_struct *tty, unsigned int cmd, 227 unsigned long arg); 228 int (*compat_ioctl)(struct tty_struct *tty, unsigned int cmd, 229 unsigned long arg); 230 void (*set_termios)(struct tty_struct *tty, const struct ktermios *old); 231 __poll_t (*poll)(struct tty_struct *tty, struct file *file, 232 struct poll_table_struct *wait); 233 void (*hangup)(struct tty_struct *tty); 234 235 /* 236 * The following routines are called from below. 237 */ 238 void (*receive_buf)(struct tty_struct *tty, const unsigned char *cp, 239 const char *fp, int count); 240 void (*write_wakeup)(struct tty_struct *tty); 241 void (*dcd_change)(struct tty_struct *tty, bool active); 242 int (*receive_buf2)(struct tty_struct *tty, const unsigned char *cp, 243 const char *fp, int count); 244 void (*lookahead_buf)(struct tty_struct *tty, const unsigned char *cp, 245 const unsigned char *fp, unsigned int count); 246 247 struct module *owner; 248 }; 249 250 struct tty_ldisc { 251 struct tty_ldisc_ops *ops; 252 struct tty_struct *tty; 253 }; 254 255 #define MODULE_ALIAS_LDISC(ldisc) \ 256 MODULE_ALIAS("tty-ldisc-" __stringify(ldisc)) 257 258 extern const struct seq_operations tty_ldiscs_seq_ops; 259 260 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *); 261 void tty_ldisc_deref(struct tty_ldisc *); 262 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *); 263 264 void tty_ldisc_flush(struct tty_struct *tty); 265 266 int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc); 267 void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc); 268 int tty_set_ldisc(struct tty_struct *tty, int disc); 269 270 #endif /* _LINUX_TTY_LDISC_H */ 271