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alsactl: use epoll(7) instead of poll(2)

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Linux kernel supports unique system call; epoll(7). This allows
applications to make associations for descriptor-unique data in a
easy way.

This commit uses epoll(7) instead of poll(2) for this point.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
This commit is contained in:
Takashi Sakamoto 2018-10-14 23:36:28 +09:00 committed by Jaroslav Kysela
parent fbc31a7593
commit 5c859fa649
1 changed files with 118 additions and 26 deletions
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144
alsactl/monitor.c
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@ -20,6 +20,9 @@
#include "aconfig.h"
#include "version.h"
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <sys/epoll.h>
#include <alsa/asoundlib.h>
#define MAX_CARDS 256
@ -114,41 +117,121 @@ static int print_event(int card, snd_ctl_t *ctl)
return 0;
}
static int run_dispatcher(snd_ctl_t **ctls, int ncards, int show_cards)
static int operate_dispatcher(int epfd, uint32_t op, struct epoll_event *epev,
snd_ctl_t *ctl)
{
struct pollfd *pfds;
int count;
unsigned int pfd_count;
int i;
int err;
count = snd_ctl_poll_descriptors_count(ctl);
if (count < 0)
return count;
if (count == 0)
return -ENXIO;
pfd_count = count;
pfds = calloc(pfd_count, sizeof(*pfds));
if (!pfds)
return -ENOMEM;
count = snd_ctl_poll_descriptors(ctl, pfds, pfd_count);
if (count < 0) {
err = count;
goto end;
}
if (count != pfd_count) {
err = -EIO;
goto end;
}
for (i = 0; i < pfd_count; ++i) {
err = epoll_ctl(epfd, op, pfds[i].fd, epev);
if (err < 0)
break;
}
end:
free(pfds);
return err;
}
static int prepare_dispatcher(int epfd, snd_ctl_t **ctls, int ncards)
{
int i;
int err = 0;
for (;ncards > 0;) {
struct pollfd fds[ncards];
int i;
for (i = 0; i < ncards; i++)
snd_ctl_poll_descriptors(ctls[i], &fds[i], 1);
err = poll(fds, ncards, -1);
if (err <= 0) {
err = 0;
for (i = 0; i < ncards; ++i) {
snd_ctl_t *ctl = ctls[i];
struct epoll_event ev;
ev.events = EPOLLIN;
ev.data.ptr = (void *)ctl;
err = operate_dispatcher(epfd, EPOLL_CTL_ADD, &ev, ctl);
if (err < 0)
break;
}
for (i = 0; i < ncards; i++) {
unsigned short revents;
snd_ctl_poll_descriptors_revents(ctls[i], &fds[i], 1,
&revents);
if (revents & POLLIN)
print_event(show_cards ? i : -1, ctls[i]);
}
}
return err;
}
static int run_dispatcher(int epfd, unsigned int max_ev_count, int show_cards)
{
struct epoll_event *epev;
int err = 0;
epev = calloc(max_ev_count, sizeof(*epev));
if (!epev)
return -ENOMEM;
while (true) {
int count;
int i;
count = epoll_wait(epfd, epev, max_ev_count, 200);
if (count < 0) {
err = count;
break;
}
if (count == 0)
continue;
for (i = 0; i < count; ++i) {
struct epoll_event *ev = epev + i;
snd_ctl_t *handle = (snd_ctl_t *)ev->data.ptr;
if (ev->events & EPOLLIN)
print_event(show_cards ? i : -1, handle);
}
}
free(epev);
return err;
}
static void clear_dispatcher(int epfd, snd_ctl_t **ctls, int ncards)
{
int i;
for (i = 0; i < ncards; ++i) {
snd_ctl_t *ctl = ctls[i];
operate_dispatcher(epfd, EPOLL_CTL_DEL, NULL, ctl);
}
}
int monitor(const char *name)
{
snd_ctl_t *ctls[MAX_CARDS];
snd_ctl_t *ctls[MAX_CARDS] = {0};
int ncards = 0;
int show_cards;
int i, err = 0;
int epfd;
int i;
int err = 0;
epfd = epoll_create(1);
if (epfd < 0)
return -errno;
if (!name) {
struct snd_card_iterator iter;
@ -170,9 +253,18 @@ int monitor(const char *name)
show_cards = 0;
}
err = run_dispatcher(ctls, ncards, show_cards);
error:
for (i = 0; i < ncards; i++)
snd_ctl_close(ctls[i]);
err = prepare_dispatcher(epfd, ctls, ncards);
if (err >= 0)
err = run_dispatcher(epfd, ncards, show_cards);
clear_dispatcher(epfd, ctls, ncards);
error:
for (i = 0; i < ncards; i++) {
if (ctls[i])
snd_ctl_close(ctls[i]);
}
close(epfd);
return err;
}