LXR linux/include/linux/poll.h

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