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#ifdef __clang__
  20#define MAX_STACK_ALLOC 768
  21#else
  22#define MAX_STACK_ALLOC 832
  23#endif
  24#define FRONTEND_STACK_ALLOC    256
  25#define SELECT_STACK_ALLOC      FRONTEND_STACK_ALLOC
  26#define POLL_STACK_ALLOC        FRONTEND_STACK_ALLOC
  27#define WQUEUES_STACK_ALLOC     (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
  28#define N_INLINE_POLL_ENTRIES   (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
  29
  30#define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)
  31
  32struct poll_table_struct;
  33
  34/* 
  35 * structures and helpers for f_op->poll implementations
  36 */
  37typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
  38
  39/*
  40 * Do not touch the structure directly, use the access functions
  41 * poll_does_not_wait() and poll_requested_events() instead.
  42 */
  43typedef struct poll_table_struct {
  44        poll_queue_proc _qproc;
  45        __poll_t _key;
  46} poll_table;
  47
  48static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
  49{
  50        if (p && p->_qproc && wait_address)
  51                p->_qproc(filp, wait_address, p);
  52}
  53
  54/*
  55 * Return true if it is guaranteed that poll will not wait. This is the case
  56 * if the poll() of another file descriptor in the set got an event, so there
  57 * is no need for waiting.
  58 */
  59static inline bool poll_does_not_wait(const poll_table *p)
  60{
  61        return p == NULL || p->_qproc == NULL;
  62}
  63
  64/*
  65 * Return the set of events that the application wants to poll for.
  66 * This is useful for drivers that need to know whether a DMA transfer has
  67 * to be started implicitly on poll(). You typically only want to do that
  68 * if the application is actually polling for POLLIN and/or POLLOUT.
  69 */
  70static inline __poll_t poll_requested_events(const poll_table *p)
  71{
  72        return p ? p->_key : ~(__poll_t)0;
  73}
  74
  75static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
  76{
  77        pt->_qproc = qproc;
  78        pt->_key   = ~(__poll_t)0; /* all events enabled */
  79}
  80
  81static inline bool file_can_poll(struct file *file)
  82{
  83        return file->f_op->poll;
  84}
  85
  86static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
  87{
  88        if (unlikely(!file->f_op->poll))
  89                return DEFAULT_POLLMASK;
  90        return file->f_op->poll(file, pt);
  91}
  92
  93struct poll_table_entry {
  94        struct file *filp;
  95        __poll_t key;
  96        wait_queue_entry_t wait;
  97        wait_queue_head_t *wait_address;
  98};
  99
 100/*
 101 * Structures and helpers for select/poll syscall
 102 */
 103struct poll_wqueues {
 104        poll_table pt;
 105        struct poll_table_page *table;
 106        struct task_struct *polling_task;
 107        int triggered;
 108        int error;
 109        int inline_index;
 110        struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
 111};
 112
 113extern void poll_initwait(struct poll_wqueues *pwq);
 114extern void poll_freewait(struct poll_wqueues *pwq);
 115extern u64 select_estimate_accuracy(struct timespec64 *tv);
 116
 117#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 118
 119extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 120                           fd_set __user *exp, struct timespec64 *end_time);
 121
 122extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
 123                                   long nsec);
 124
 125#define __MAP(v, from, to) \
 126        (from < to ? (v & from) * (to/from) : (v & from) / (from/to))
 127
 128static inline __u16 mangle_poll(__poll_t val)
 129{
 130        __u16 v = (__force __u16)val;
 131#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
 132        return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
 133                M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
 134                M(HUP) | M(RDHUP) | M(MSG);
 135#undef M
 136}
 137
 138static inline __poll_t demangle_poll(u16 val)
 139{
 140#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
 141        return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
 142                M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
 143                M(HUP) | M(RDHUP) | M(MSG);
 144#undef M
 145}
 146#undef __MAP
 147
 148
 149#endif /* _LINUX_POLL_H */
 150