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 /* 8 * This structure defines the interface between the tty line discipline 9 * implementation and the tty routines. The following routines can be 10 * defined; unless noted otherwise, they are optional, and can be 11 * filled in with a null pointer. 12 * 13 * int (*open)(struct tty_struct *); 14 * 15 * This function is called when the line discipline is associated 16 * with the tty. The line discipline can use this as an 17 * opportunity to initialize any state needed by the ldisc routines. 18 * 19 * void (*close)(struct tty_struct *); 20 * 21 * This function is called when the line discipline is being 22 * shutdown, either because the tty is being closed or because 23 * the tty is being changed to use a new line discipline 24 * 25 * void (*flush_buffer)(struct tty_struct *tty); 26 * 27 * This function instructs the line discipline to clear its 28 * buffers of any input characters it may have queued to be 29 * delivered to the user mode process. 30 * 31 * ssize_t (*read)(struct tty_struct * tty, struct file * file, 32 * unsigned char * buf, size_t nr); 33 * 34 * This function is called when the user requests to read from 35 * the tty. The line discipline will return whatever characters 36 * it has buffered up for the user. If this function is not 37 * defined, the user will receive an EIO error. 38 * 39 * ssize_t (*write)(struct tty_struct * tty, struct file * file, 40 * const unsigned char * buf, size_t nr); 41 * 42 * This function is called when the user requests to write to the 43 * tty. The line discipline will deliver the characters to the 44 * low-level tty device for transmission, optionally performing 45 * some processing on the characters first. If this function is 46 * not defined, the user will receive an EIO error. 47 * 48 * int (*ioctl)(struct tty_struct * tty, struct file * file, 49 * unsigned int cmd, unsigned long arg); 50 * 51 * This function is called when the user requests an ioctl which 52 * is not handled by the tty layer or the low-level tty driver. 53 * It is intended for ioctls which affect line discpline 54 * operation. Note that the search order for ioctls is (1) tty 55 * layer, (2) tty low-level driver, (3) line discpline. So a 56 * low-level driver can "grab" an ioctl request before the line 57 * discpline has a chance to see it. 58 * 59 * int (*compat_ioctl)(struct tty_struct * tty, struct file * file, 60 * unsigned int cmd, unsigned long arg); 61 * 62 * Process ioctl calls from 32-bit process on 64-bit system 63 * 64 * NOTE: only ioctls that are neither "pointer to compatible 65 * structure" nor tty-generic. Something private that takes 66 * an integer or a pointer to wordsize-sensitive structure 67 * belongs here, but most of ldiscs will happily leave 68 * it NULL. 69 * 70 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old); 71 * 72 * This function notifies the line discpline that a change has 73 * been made to the termios structure. 74 * 75 * int (*poll)(struct tty_struct * tty, struct file * file, 76 * poll_table *wait); 77 * 78 * This function is called when a user attempts to select/poll on a 79 * tty device. It is solely the responsibility of the line 80 * discipline to handle poll requests. 81 * 82 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 83 * char *fp, int count); 84 * 85 * This function is called by the low-level tty driver to send 86 * characters received by the hardware to the line discpline for 87 * processing. <cp> is a pointer to the buffer of input 88 * character received by the device. <fp> is a pointer to a 89 * pointer of flag bytes which indicate whether a character was 90 * received with a parity error, etc. <fp> may be NULL to indicate 91 * all data received is TTY_NORMAL. 92 * 93 * void (*write_wakeup)(struct tty_struct *); 94 * 95 * This function is called by the low-level tty driver to signal 96 * that line discpline should try to send more characters to the 97 * low-level driver for transmission. If the line discpline does 98 * not have any more data to send, it can just return. If the line 99 * discipline does have some data to send, please arise a tasklet 100 * or workqueue to do the real data transfer. Do not send data in 101 * this hook, it may leads to a deadlock. 102 * 103 * int (*hangup)(struct tty_struct *) 104 * 105 * Called on a hangup. Tells the discipline that it should 106 * cease I/O to the tty driver. Can sleep. The driver should 107 * seek to perform this action quickly but should wait until 108 * any pending driver I/O is completed. 109 * 110 * void (*dcd_change)(struct tty_struct *tty, unsigned int status) 111 * 112 * Tells the discipline that the DCD pin has changed its status. 113 * Used exclusively by the N_PPS (Pulse-Per-Second) line discipline. 114 * 115 * int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 116 * char *fp, int count); 117 * 118 * This function is called by the low-level tty driver to send 119 * characters received by the hardware to the line discpline for 120 * processing. <cp> is a pointer to the buffer of input 121 * character received by the device. <fp> is a pointer to a 122 * pointer of flag bytes which indicate whether a character was 123 * received with a parity error, etc. <fp> may be NULL to indicate 124 * all data received is TTY_NORMAL. 125 * If assigned, prefer this function for automatic flow control. 126 */ 127 128 #include <linux/fs.h> 129 #include <linux/wait.h> 130 #include <linux/atomic.h> 131 #include <linux/list.h> 132 #include <linux/lockdep.h> 133 #include <linux/seq_file.h> 134 135 /* 136 * the semaphore definition 137 */ 138 struct ld_semaphore { 139 atomic_long_t count; 140 raw_spinlock_t wait_lock; 141 unsigned int wait_readers; 142 struct list_head read_wait; 143 struct list_head write_wait; 144 #ifdef CONFIG_DEBUG_LOCK_ALLOC 145 struct lockdep_map dep_map; 146 #endif 147 }; 148 149 void __init_ldsem(struct ld_semaphore *sem, const char *name, 150 struct lock_class_key *key); 151 152 #define init_ldsem(sem) \ 153 do { \ 154 static struct lock_class_key __key; \ 155 \ 156 __init_ldsem((sem), #sem, &__key); \ 157 } while (0) 158 159 160 int ldsem_down_read(struct ld_semaphore *sem, long timeout); 161 int ldsem_down_read_trylock(struct ld_semaphore *sem); 162 int ldsem_down_write(struct ld_semaphore *sem, long timeout); 163 int ldsem_down_write_trylock(struct ld_semaphore *sem); 164 void ldsem_up_read(struct ld_semaphore *sem); 165 void ldsem_up_write(struct ld_semaphore *sem); 166 167 #ifdef CONFIG_DEBUG_LOCK_ALLOC 168 int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass, 169 long timeout); 170 int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, 171 long timeout); 172 #else 173 # define ldsem_down_read_nested(sem, subclass, timeout) \ 174 ldsem_down_read(sem, timeout) 175 # define ldsem_down_write_nested(sem, subclass, timeout) \ 176 ldsem_down_write(sem, timeout) 177 #endif 178 179 180 struct tty_ldisc_ops { 181 char *name; 182 int num; 183 184 /* 185 * The following routines are called from above. 186 */ 187 int (*open)(struct tty_struct *); 188 void (*close)(struct tty_struct *); 189 void (*flush_buffer)(struct tty_struct *tty); 190 ssize_t (*read)(struct tty_struct *tty, struct file *file, 191 unsigned char *buf, size_t nr, 192 void **cookie, unsigned long offset); 193 ssize_t (*write)(struct tty_struct *tty, struct file *file, 194 const unsigned char *buf, size_t nr); 195 int (*ioctl)(struct tty_struct *tty, struct file *file, 196 unsigned int cmd, unsigned long arg); 197 int (*compat_ioctl)(struct tty_struct *tty, struct file *file, 198 unsigned int cmd, unsigned long arg); 199 void (*set_termios)(struct tty_struct *tty, struct ktermios *old); 200 __poll_t (*poll)(struct tty_struct *, struct file *, 201 struct poll_table_struct *); 202 void (*hangup)(struct tty_struct *tty); 203 204 /* 205 * The following routines are called from below. 206 */ 207 void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 208 const char *fp, int count); 209 void (*write_wakeup)(struct tty_struct *); 210 void (*dcd_change)(struct tty_struct *, unsigned int); 211 int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 212 const char *fp, int count); 213 214 struct module *owner; 215 }; 216 217 struct tty_ldisc { 218 struct tty_ldisc_ops *ops; 219 struct tty_struct *tty; 220 }; 221 222 #define MODULE_ALIAS_LDISC(ldisc) \ 223 MODULE_ALIAS("tty-ldisc-" __stringify(ldisc)) 224 225 extern const struct seq_operations tty_ldiscs_seq_ops; 226 227 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *); 228 void tty_ldisc_deref(struct tty_ldisc *); 229 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *); 230 231 void tty_ldisc_flush(struct tty_struct *tty); 232 233 int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc); 234 void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc); 235 int tty_set_ldisc(struct tty_struct *tty, int disc); 236 237 #endif /* _LINUX_TTY_LDISC_H */ 238