1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_POLL_H
3#define _LINUX_POLL_H
4
5
6#include <linux/compiler.h>
7#include <linux/ktime.h>
8#include <linux/wait.h>
9#include <linux/string.h>
10#include <linux/fs.h>
11#include <linux/uaccess.h>
12#include <uapi/linux/poll.h>
13#include <uapi/linux/eventpoll.h>
14
15/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
16 additional memory. */
17#ifdef __clang__
18#define MAX_STACK_ALLOC 768
19#else
20#define MAX_STACK_ALLOC 832
21#endif
22#define FRONTEND_STACK_ALLOC 256
23#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
24#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
25#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
26#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
27
28#define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)
29
30struct poll_table_struct;
31
32/*
33 * structures and helpers for f_op->poll implementations
34 */
35typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
36
37/*
38 * Do not touch the structure directly, use the access functions
39 * poll_does_not_wait() and poll_requested_events() instead.
40 */
41typedef struct poll_table_struct {
42 poll_queue_proc _qproc;
43 __poll_t _key;
44} poll_table;
45
46static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
47{
48 if (p && p->_qproc && wait_address)
49 p->_qproc(filp, wait_address, p);
50}
51
52/*
53 * Return true if it is guaranteed that poll will not wait. This is the case
54 * if the poll() of another file descriptor in the set got an event, so there
55 * is no need for waiting.
56 */
57static inline bool poll_does_not_wait(const poll_table *p)
58{
59 return p == NULL || p->_qproc == NULL;
60}
61
62/*
63 * Return the set of events that the application wants to poll for.
64 * This is useful for drivers that need to know whether a DMA transfer has
65 * to be started implicitly on poll(). You typically only want to do that
66 * if the application is actually polling for POLLIN and/or POLLOUT.
67 */
68static inline __poll_t poll_requested_events(const poll_table *p)
69{
70 return p ? p->_key : ~(__poll_t)0;
71}
72
73static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
74{
75 pt->_qproc = qproc;
76 pt->_key = ~(__poll_t)0; /* all events enabled */
77}
78
79static inline bool file_can_poll(struct file *file)
80{
81 return file->f_op->poll;
82}
83
84static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
85{
86 if (unlikely(!file->f_op->poll))
87 return DEFAULT_POLLMASK;
88 return file->f_op->poll(file, pt);
89}
90
91struct poll_table_entry {
92 struct file *filp;
93 __poll_t key;
94 wait_queue_entry_t wait;
95 wait_queue_head_t *wait_address;
96};
97
98/*
99 * Structures and helpers for select/poll syscall
100 */
101struct poll_wqueues {
102 poll_table pt;
103 struct poll_table_page *table;
104 struct task_struct *polling_task;
105 int triggered;
106 int error;
107 int inline_index;
108 struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
109};
110
111extern void poll_initwait(struct poll_wqueues *pwq);
112extern void poll_freewait(struct poll_wqueues *pwq);
113extern u64 select_estimate_accuracy(struct timespec64 *tv);
114
115#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
116
117extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
118 fd_set __user *exp, struct timespec64 *end_time);
119
120extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
121 long nsec);
122
123#define __MAP(v, from, to) \
124 (from < to ? (v & from) * (to/from) : (v & from) / (from/to))
125
126static inline __u16 mangle_poll(__poll_t val)
127{
128 __u16 v = (__force __u16)val;
129#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
130 return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
131 M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
132 M(HUP) | M(RDHUP) | M(MSG);
133#undef M
134}
135
136static inline __poll_t demangle_poll(u16 val)
137{
138#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
139 return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
140 M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
141 M(HUP) | M(RDHUP) | M(MSG);
142#undef M
143}
144#undef __MAP
145
146
147#endif /* _LINUX_POLL_H */
148

source code of linux/include/linux/poll.h