root/include/linux/poll.h

INCLUDED FROM

DEFINITIONS

1. poll_wait
2. poll_does_not_wait
3. poll_requested_events
4. init_poll_funcptr
5. file_can_poll
6. vfs_poll
7. mangle_poll
8. demangle_poll

   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 
  16 extern 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 
  32 struct poll_table_struct;
  33 
  34 /* 
  35  * structures and helpers for f_op->poll implementations
  36  */
  37 typedef 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  */
  43 typedef struct poll_table_struct {
  44         poll_queue_proc _qproc;
  45         __poll_t _key;
  46 } poll_table;
  47 
  48 static 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  */
  59 static 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  */
  70 static inline __poll_t poll_requested_events(const poll_table *p)
  71 {
  72         return p ? p->_key : ~(__poll_t)0;
  73 }
  74 
  75 static 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 
  81 static inline bool file_can_poll(struct file *file)
  82 {
  83         return file->f_op->poll;
  84 }
  85 
  86 static 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 
  93 struct 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  */
 103 struct 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 
 113 extern void poll_initwait(struct poll_wqueues *pwq);
 114 extern void poll_freewait(struct poll_wqueues *pwq);
 115 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 116 
 117 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 118 
 119 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 120                            fd_set __user *exp, struct timespec64 *end_time);
 121 
 122 extern 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 
 128 static 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 
 138 static 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 */