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 * long (*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 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old); 63 * 64 * This function notifies the line discpline that a change has 65 * been made to the termios structure. 66 * 67 * int (*poll)(struct tty_struct * tty, struct file * file, 68 * poll_table *wait); 69 * 70 * This function is called when a user attempts to select/poll on a 71 * tty device. It is solely the responsibility of the line 72 * discipline to handle poll requests. 73 * 74 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 75 * char *fp, int count); 76 * 77 * This function is called by the low-level tty driver to send 78 * characters received by the hardware to the line discpline for 79 * processing. <cp> is a pointer to the buffer of input 80 * character received by the device. <fp> is a pointer to a 81 * pointer of flag bytes which indicate whether a character was 82 * received with a parity error, etc. <fp> may be NULL to indicate 83 * all data received is TTY_NORMAL. 84 * 85 * void (*write_wakeup)(struct tty_struct *); 86 * 87 * This function is called by the low-level tty driver to signal 88 * that line discpline should try to send more characters to the 89 * low-level driver for transmission. If the line discpline does 90 * not have any more data to send, it can just return. If the line 91 * discipline does have some data to send, please arise a tasklet 92 * or workqueue to do the real data transfer. Do not send data in 93 * this hook, it may leads to a deadlock. 94 * 95 * int (*hangup)(struct tty_struct *) 96 * 97 * Called on a hangup. Tells the discipline that it should 98 * cease I/O to the tty driver. Can sleep. The driver should 99 * seek to perform this action quickly but should wait until 100 * any pending driver I/O is completed. 101 * 102 * void (*dcd_change)(struct tty_struct *tty, unsigned int status) 103 * 104 * Tells the discipline that the DCD pin has changed its status. 105 * Used exclusively by the N_PPS (Pulse-Per-Second) line discipline. 106 * 107 * int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 108 * char *fp, int count); 109 * 110 * This function is called by the low-level tty driver to send 111 * characters received by the hardware to the line discpline for 112 * processing. <cp> is a pointer to the buffer of input 113 * character received by the device. <fp> is a pointer to a 114 * pointer of flag bytes which indicate whether a character was 115 * received with a parity error, etc. <fp> may be NULL to indicate 116 * all data received is TTY_NORMAL. 117 * If assigned, prefer this function for automatic flow control. 118 */ 119 120 #include <linux/fs.h> 121 #include <linux/wait.h> 122 #include <linux/atomic.h> 123 124 /* 125 * the semaphore definition 126 */ 127 struct ld_semaphore { 128 atomic_long_t count; 129 raw_spinlock_t wait_lock; 130 unsigned int wait_readers; 131 struct list_head read_wait; 132 struct list_head write_wait; 133 #ifdef CONFIG_DEBUG_LOCK_ALLOC 134 struct lockdep_map dep_map; 135 #endif 136 }; 137 138 extern void __init_ldsem(struct ld_semaphore *sem, const char *name, 139 struct lock_class_key *key); 140 141 #define init_ldsem(sem) \ 142 do { \ 143 static struct lock_class_key __key; \ 144 \ 145 __init_ldsem((sem), #sem, &__key); \ 146 } while (0) 147 148 149 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout); 150 extern int ldsem_down_read_trylock(struct ld_semaphore *sem); 151 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout); 152 extern int ldsem_down_write_trylock(struct ld_semaphore *sem); 153 extern void ldsem_up_read(struct ld_semaphore *sem); 154 extern void ldsem_up_write(struct ld_semaphore *sem); 155 156 #ifdef CONFIG_DEBUG_LOCK_ALLOC 157 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass, 158 long timeout); 159 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass, 160 long timeout); 161 #else 162 # define ldsem_down_read_nested(sem, subclass, timeout) \ 163 ldsem_down_read(sem, timeout) 164 # define ldsem_down_write_nested(sem, subclass, timeout) \ 165 ldsem_down_write(sem, timeout) 166 #endif 167 168 169 struct tty_ldisc_ops { 170 int magic; 171 char *name; 172 int num; 173 int flags; 174 175 /* 176 * The following routines are called from above. 177 */ 178 int (*open)(struct tty_struct *); 179 void (*close)(struct tty_struct *); 180 void (*flush_buffer)(struct tty_struct *tty); 181 ssize_t (*read)(struct tty_struct *tty, struct file *file, 182 unsigned char __user *buf, size_t nr); 183 ssize_t (*write)(struct tty_struct *tty, struct file *file, 184 const unsigned char *buf, size_t nr); 185 int (*ioctl)(struct tty_struct *tty, struct file *file, 186 unsigned int cmd, unsigned long arg); 187 long (*compat_ioctl)(struct tty_struct *tty, struct file *file, 188 unsigned int cmd, unsigned long arg); 189 void (*set_termios)(struct tty_struct *tty, struct ktermios *old); 190 __poll_t (*poll)(struct tty_struct *, struct file *, 191 struct poll_table_struct *); 192 int (*hangup)(struct tty_struct *tty); 193 194 /* 195 * The following routines are called from below. 196 */ 197 void (*receive_buf)(struct tty_struct *, const unsigned char *cp, 198 char *fp, int count); 199 void (*write_wakeup)(struct tty_struct *); 200 void (*dcd_change)(struct tty_struct *, unsigned int); 201 int (*receive_buf2)(struct tty_struct *, const unsigned char *cp, 202 char *fp, int count); 203 204 struct module *owner; 205 206 int refcount; 207 }; 208 209 struct tty_ldisc { 210 struct tty_ldisc_ops *ops; 211 struct tty_struct *tty; 212 }; 213 214 #define TTY_LDISC_MAGIC 0x5403 215 216 #define LDISC_FLAG_DEFINED 0x00000001 217 218 #define MODULE_ALIAS_LDISC(ldisc) \ 219 MODULE_ALIAS("tty-ldisc-" __stringify(ldisc)) 220 221 #endif /* _LINUX_TTY_LDISC_H */ 222
