linux/include/linux/poll.h
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   1#ifndef _LINUX_POLL_H
   2#define _LINUX_POLL_H
   3
   4
   5#include <linux/compiler.h>
   6#include <linux/ktime.h>
   7#include <linux/wait.h>
   8#include <linux/string.h>
   9#include <linux/fs.h>
  10#include <linux/sysctl.h>
  11#include <asm/uaccess.h>
  12#include <uapi/linux/poll.h>
  13
  14extern struct ctl_table epoll_table[]; /* for sysctl */
  15/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
  16   additional memory. */
  17#define MAX_STACK_ALLOC 832
  18#define FRONTEND_STACK_ALLOC    256
  19#define SELECT_STACK_ALLOC      FRONTEND_STACK_ALLOC
  20#define POLL_STACK_ALLOC        FRONTEND_STACK_ALLOC
  21#define WQUEUES_STACK_ALLOC     (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
  22#define N_INLINE_POLL_ENTRIES   (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
  23
  24#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
  25
  26struct poll_table_struct;
  27
  28/* 
  29 * structures and helpers for f_op->poll implementations
  30 */
  31typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
  32
  33/*
  34 * Do not touch the structure directly, use the access functions
  35 * poll_does_not_wait() and poll_requested_events() instead.
  36 */
  37typedef struct poll_table_struct {
  38        poll_queue_proc _qproc;
  39        unsigned long _key;
  40} poll_table;
  41
  42static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
  43{
  44        if (p && p->_qproc && wait_address)
  45                p->_qproc(filp, wait_address, p);
  46}
  47
  48/*
  49 * Return true if it is guaranteed that poll will not wait. This is the case
  50 * if the poll() of another file descriptor in the set got an event, so there
  51 * is no need for waiting.
  52 */
  53static inline bool poll_does_not_wait(const poll_table *p)
  54{
  55        return p == NULL || p->_qproc == NULL;
  56}
  57
  58/*
  59 * Return the set of events that the application wants to poll for.
  60 * This is useful for drivers that need to know whether a DMA transfer has
  61 * to be started implicitly on poll(). You typically only want to do that
  62 * if the application is actually polling for POLLIN and/or POLLOUT.
  63 */
  64static inline unsigned long poll_requested_events(const poll_table *p)
  65{
  66        return p ? p->_key : ~0UL;
  67}
  68
  69static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
  70{
  71        pt->_qproc = qproc;
  72        pt->_key   = ~0UL; /* all events enabled */
  73}
  74
  75struct poll_table_entry {
  76        struct file *filp;
  77        unsigned long key;
  78        wait_queue_t wait;
  79        wait_queue_head_t *wait_address;
  80};
  81
  82/*
  83 * Structures and helpers for select/poll syscall
  84 */
  85struct poll_wqueues {
  86        poll_table pt;
  87        struct poll_table_page *table;
  88        struct task_struct *polling_task;
  89        int triggered;
  90        int error;
  91        int inline_index;
  92        struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
  93};
  94
  95extern void poll_initwait(struct poll_wqueues *pwq);
  96extern void poll_freewait(struct poll_wqueues *pwq);
  97extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
  98                                 ktime_t *expires, unsigned long slack);
  99extern long select_estimate_accuracy(struct timespec *tv);
 100
 101
 102static inline int poll_schedule(struct poll_wqueues *pwq, int state)
 103{
 104        return poll_schedule_timeout(pwq, state, NULL, 0);
 105}
 106
 107/*
 108 * Scalable version of the fd_set.
 109 */
 110
 111typedef struct {
 112        unsigned long *in, *out, *ex;
 113        unsigned long *res_in, *res_out, *res_ex;
 114} fd_set_bits;
 115
 116/*
 117 * How many longwords for "nr" bits?
 118 */
 119#define FDS_BITPERLONG  (8*sizeof(long))
 120#define FDS_LONGS(nr)   (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
 121#define FDS_BYTES(nr)   (FDS_LONGS(nr)*sizeof(long))
 122
 123/*
 124 * We do a VERIFY_WRITE here even though we are only reading this time:
 125 * we'll write to it eventually..
 126 *
 127 * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
 128 */
 129static inline
 130int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
 131{
 132        nr = FDS_BYTES(nr);
 133        if (ufdset)
 134                return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
 135
 136        memset(fdset, 0, nr);
 137        return 0;
 138}
 139
 140static inline unsigned long __must_check
 141set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
 142{
 143        if (ufdset)
 144                return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
 145        return 0;
 146}
 147
 148static inline
 149void zero_fd_set(unsigned long nr, unsigned long *fdset)
 150{
 151        memset(fdset, 0, FDS_BYTES(nr));
 152}
 153
 154#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 155
 156extern int do_select(int n, fd_set_bits *fds, struct timespec *end_time);
 157extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
 158                       struct timespec *end_time);
 159extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 160                           fd_set __user *exp, struct timespec *end_time);
 161
 162extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);
 163
 164#endif /* _LINUX_POLL_H */
 165
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