include/linux/poll.h

   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 <linux/uaccess.h>
  12 #include <uapi/linux/poll.h>
  13
  14 extern 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
  26 struct poll_table_struct;
  27
  28 /*
  29  * structures and helpers for f_op->poll implementations
  30  */
  31 typedef 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  */
  37 typedef struct poll_table_struct {
  38         poll_queue_proc _qproc;
  39         unsigned long _key;
  40 } poll_table;
  41
  42 static 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  */
  53 static 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  */
  64 static inline unsigned long poll_requested_events(const poll_table *p)
  65 {
  66         return p ? p->_key : ~0UL;
  67 }
  68
  69 static 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
  75 struct poll_table_entry {
  76         struct file *filp;
  77         unsigned long key;
  78         wait_queue_entry_t wait;
  79         wait_queue_head_t *wait_address;
  80 };
  81
  82 /*
  83  * Structures and helpers for select/poll syscall
  84  */
  85 struct 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
  95 extern void poll_initwait(struct poll_wqueues *pwq);
  96 extern void poll_freewait(struct poll_wqueues *pwq);
  97 extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
  98                                  ktime_t *expires, unsigned long slack);
  99 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 100
 101 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 102
 103 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 104                            fd_set __user *exp, struct timespec64 *end_time);
 105
 106 extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
 107                                    long nsec);
 108
 109 #endif /* _LINUX_POLL_H */