1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_TTY_LDISC_H 3 #define _LINUX_TTY_LDISC_H 4 5 /* 6 * This structure defines the interface between the tty line discipline 7 * implementation and the tty routines. The following routines can be 8 * defined; unless noted otherwise, they are optional, and can be 9 * filled in with a null pointer. 10 * 11 * int (*open)(struct tty_struct *); 12 * 13 * This function is called when the line discipline is associated 14 * with the tty. The line discipline can use this as an 15 * opportunity to initialize any state needed by the ldisc routines. 16 * 17 * void (*close)(struct tty_struct *); 18 * 19 * This function is called when the line discipline is being 20 * shutdown, either because the tty is being closed or because 21 * the tty is being changed to use a new line discipline 22 * 23 * void (*flush_buffer)(struct tty_struct *tty); 24 * 25 * This function instructs the line discipline to clear its 26 * buffers of any input characters it may have queued to be 27 * delivered to the user mode process. 28 * 29 * ssize_t (*read)(struct tty_struct * tty, struct file * file, 30 * unsigned char * buf, size_t nr); 31 * 32 * This function is called when the user requests to read from 33 * the tty. The line discipline will return whatever characters 34 * it has buffered up for the user. If this function is not 35 * defined, the user will receive an EIO error. 36 * 37 * ssize_t (*write)(struct tty_struct * tty, struct file * file, 38 * const unsigned char * buf, size_t nr); 39 * 40 * This function is called when the user requests to write to the 41 * tty. The line discipline will deliver the characters to the 42 * low-level tty device for transmission, optionally performing 43 * some processing on the characters first. If this function is 44 * not defined, the user will receive an EIO error. 45 * 46 * int (*ioctl)(struct tty_struct * tty, struct file * file, 47 * unsigned int cmd, unsigned long arg); 48 * 49 * This function is called when the user requests an ioctl which 50 * is not handled by the tty layer or the low-level tty driver. 51 * It is intended for ioctls which affect line discpline 52 * operation. Note that the search order for ioctls is (1) tty 53 * layer, (2) tty low-level driver, (3) line discpline. So a 54 * low-level driver can "grab" an ioctl request before the line 55 * discpline has a chance to see it. 56 * 57 * int (*compat_ioctl)(struct tty_struct * tty, struct file * file, 58 * unsigned int cmd, unsigned long arg); 59 * 60 * Process ioctl calls from 32-bit process on 64-bit system 61 * 62 * NOTE: only ioctls that are neither "pointer to compatible 63 * structure" nor tty-generic. Something private that takes 64 * an integer or a pointer to wordsize-sensitive structure 65 * belongs here, but most of ldiscs will happily leave 66 * it NULL. 67 * 68 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old); 69 * 70 * This function notifies the line discpline that a change has 71 * been made to the termios structure. 72 * 73 * int (*poll)(struct tty_struct * tty, struct file * file, 74 * poll_table *wait); 75 * 76 * This function is called when a user attempts to select/poll on a 77 * tty device. It is solely the responsibility of the line 78 * discipline to handle poll requests. 79 * 80 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 81 * char *fp, int count); 82 * 83 * This function is called by the low-level tty driver to send 84 * characters received by the hardware to the line discpline for 85 * processing. <cp> is a pointer to the buffer of input 86 * character received by the device. <fp> is a pointer to a 87 * pointer of flag bytes which indicate whether a character was 88 * received with a parity error, etc. <fp> may be NULL to indicate 89 * all data received is TTY_NORMAL. 90 * 91 * void (*write_wakeup)(struct tty_struct *); 92 * 93 * This function is called by the low-level tty driver to signal 94 * that line discpline should try to send more characters to the 95 * low-level driver for transmission. If the line discpline does 96 * not have any more data to send, it can just return. If the line 97 * discipline does have some data to send, please arise a tasklet 98 * or workqueue to do the real data transfer. Do not send data in 99 * this hook, it may leads to a deadlock. 100 * 101 * int (*hangup)(struct tty_struct *) 102 * 103 * Called on a hangup. Tells the discipline that it should 104 * cease I/O to the tty driver. Can sleep. The driver should 105 * seek to perform this action quickly but should wait until 106 * any pending driver I/O is completed. 107 * 108 * void (*dcd_change)(struct tty_struct *tty, unsigned int status) 109 * 110 * Tells the discipline that the DCD pin has changed its status. 111 * Used exclusively by the N_PPS (Pulse-Per-Second) line discipline. 112 * 113 * int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 114 * char *fp, int count); 115 * 116 * This function is called by the low-level tty driver to send 117 * characters received by the hardware to the line discpline for 118 * processing. <cp> is a pointer to the buffer of input 119 * character received by the device. <fp> is a pointer to a 120 * pointer of flag bytes which indicate whether a character was 121 * received with a parity error, etc. <fp> may be NULL to indicate 122 * all data received is TTY_NORMAL. 123 * If assigned, prefer this function for automatic flow control. 124 */ 125 126 #include <linux/fs.h> 127 #include <linux/wait.h> 128 #include <linux/atomic.h> 129 130 /* 131 * the semaphore definition 132 */ 133 struct ld_semaphore { 134 atomic_long_t count; 135 raw_spinlock_t wait_lock; 136 unsigned int wait_readers; 137 struct list_head read_wait; 138 struct list_head write_wait; 139 #ifdef CONFIG_DEBUG_LOCK_ALLOC 140 struct lockdep_map dep_map; 141 #endif 142 }; 143 144 extern void __init_ldsem(struct ld_semaphore *sem, const char *name, 145 struct lock_class_key *key); 146 147 #define init_ldsem(sem) \ 148 do { \ 149 static struct lock_class_key __key; \ 150 \ 151 __init_ldsem((sem), #sem, &__key); \ 152 } while (0) 153 154 155 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout); 156 extern int ldsem_down_read_trylock(struct ld_semaphore *sem); 157 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout); 158 extern int ldsem_down_write_trylock(struct ld_semaphore *sem); 159 extern void ldsem_up_read(struct ld_semaphore *sem); 160 extern void ldsem_up_write(struct ld_semaphore *sem); 161 162 #ifdef CONFIG_DEBUG_LOCK_ALLOC 163 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass, 164 long timeout); 165 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, 166 long timeout); 167 #else 168 # define ldsem_down_read_nested(sem, subclass, timeout) \ 169 ldsem_down_read(sem, timeout) 170 # define ldsem_down_write_nested(sem, subclass, timeout) \ 171 ldsem_down_write(sem, timeout) 172 #endif 173 174 175 struct tty_ldisc_ops { 176 char *name; 177 int num; 178 int flags; 179 180 /* 181 * The following routines are called from above. 182 */ 183 int (*open)(struct tty_struct *); 184 void (*close)(struct tty_struct *); 185 void (*flush_buffer)(struct tty_struct *tty); 186 ssize_t (*read)(struct tty_struct *tty, struct file *file, 187 unsigned char *buf, size_t nr, 188 void **cookie, unsigned long offset); 189 ssize_t (*write)(struct tty_struct *tty, struct file *file, 190 const unsigned char *buf, size_t nr); 191 int (*ioctl)(struct tty_struct *tty, struct file *file, 192 unsigned int cmd, unsigned long arg); 193 int (*compat_ioctl)(struct tty_struct *tty, struct file *file, 194 unsigned int cmd, unsigned long arg); 195 void (*set_termios)(struct tty_struct *tty, struct ktermios *old); 196 __poll_t (*poll)(struct tty_struct *, struct file *, 197 struct poll_table_struct *); 198 int (*hangup)(struct tty_struct *tty); 199 200 /* 201 * The following routines are called from below. 202 */ 203 void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 204 const char *fp, int count); 205 void (*write_wakeup)(struct tty_struct *); 206 void (*dcd_change)(struct tty_struct *, unsigned int); 207 int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 208 const char *fp, int count); 209 210 struct module *owner; 211 }; 212 213 struct tty_ldisc { 214 struct tty_ldisc_ops *ops; 215 struct tty_struct *tty; 216 }; 217 218 #define LDISC_FLAG_DEFINED 0x00000001 219 220 #define MODULE_ALIAS_LDISC(ldisc) \ 221 MODULE_ALIAS("tty-ldisc-" __stringify(ldisc)) 222 223 #endif /* _LINUX_TTY_LDISC_H */ 224