Quelle poll.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_POLL_H
#define _LINUX_POLL_H

#include <linux/compiler.h>
#include <linux/ktime.h>
#include <linux/wait.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <uapi/linux/poll.h>
#include <uapi/linux/eventpoll.h>

/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
   additional memory. */
#define MAX_STACK_ALLOC 832
#define FRONTEND_STACK_ALLOC 256
#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))

#define DEFAULT_POLLMASK (EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM)

struct poll_table_struct;

/*
* structures and helpers for f_op->poll implementations
*/
typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);

/*
* Do not touch the structure directly, use the access function
* poll_requested_events() instead.
*/
typedef struct poll_table_struct {
poll_queue_proc _qproc;
__poll_t _key;
} poll_table;

static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
{
if (p && p->_qproc) {
  p->_qproc(filp, wait_address, p);
  /*
* This memory barrier is paired in the wq_has_sleeper().
* See the comment above prepare_to_wait(), we need to
* ensure that subsequent tests in this thread can't be
* reordered with __add_wait_queue() in _qproc() paths.
*/
  smp_mb();
}
}

/*
* Return the set of events that the application wants to poll for.
* This is useful for drivers that need to know whether a DMA transfer has
* to be started implicitly on poll(). You typically only want to do that
* if the application is actually polling for POLLIN and/or POLLOUT.
*/
static inline __poll_t poll_requested_events(const poll_table *p)
{
return p ? p->_key : ~(__poll_t)0;
}

static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
{
pt->_qproc = qproc;
pt->_key   = ~(__poll_t)0; /* all events enabled */
}

static inline bool file_can_poll(struct file *file)
{
return file->f_op->poll;
}

static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
{
if (unlikely(!file->f_op->poll))
  return DEFAULT_POLLMASK;
return file->f_op->poll(file, pt);
}

struct poll_table_entry {
struct file *filp;
__poll_t key;
wait_queue_entry_t wait;
wait_queue_head_t *wait_address;
};

/*
* Structures and helpers for select/poll syscall
*/
struct poll_wqueues {
poll_table pt;
struct poll_table_page *table;
struct task_struct *polling_task;
int triggered;
int error;
int inline_index;
struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
};

extern void poll_initwait(struct poll_wqueues *pwq);
extern void poll_freewait(struct poll_wqueues *pwq);
extern u64 select_estimate_accuracy(struct timespec64 *tv);

#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)

extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
      fd_set __user *exp, struct timespec64 *end_time);

extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
       long nsec);

#define __MAP(v, from, to) \
(from < to ? (v & from) * (to/from) : (v & from) / (from/to))

static inline __u16 mangle_poll(__poll_t val)
{
__u16 v = (__force __u16)val;
#define M(X) __MAP(v, (__force __u16)EPOLL##X, POLL##X)
return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
  M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
  M(HUP) | M(RDHUP) | M(MSG);
#undef M
}

static inline __poll_t demangle_poll(u16 val)
{
#define M(X) (__force __poll_t)__MAP(val, POLL##X, (__force __u16)EPOLL##X)
return M(IN) | M(OUT) | M(PRI) | M(ERR) | M(NVAL) |
  M(RDNORM) | M(RDBAND) | M(WRNORM) | M(WRBAND) |
  M(HUP) | M(RDHUP) | M(MSG);
#undef M
}
#undef __MAP

#endif /* _LINUX_POLL_H */

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