From 02a74cc0b499f6a93c25ea8cd392af977298d60a Mon Sep 17 00:00:00 2001
From: spv <spv@spv.sh>
Date: Sun, 21 Sep 2025 00:59:56 -0400
Subject: use signal ipc instead of sleep loop

---
 src/common.h          |  1 +
 src/keypress_thread.c |  8 +++++++-
 src/light_thread.c    | 27 +++++++++++++++++++--------
 src/main.c            | 11 +++++++----
 4 files changed, 34 insertions(+), 13 deletions(-)

(limited to 'src')

diff --git a/src/common.h b/src/common.h
index 4c01c24..07cc4ae 100644
--- a/src/common.h
+++ b/src/common.h
@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdint.h>
+#include <signal.h>
 
 #include "consts.h"
 
diff --git a/src/keypress_thread.c b/src/keypress_thread.c
index 47fb1de..a174968 100644
--- a/src/keypress_thread.c
+++ b/src/keypress_thread.c
@@ -5,13 +5,19 @@
 
 #include "common.h"
 
+static pid_t light_pid;
+
 void on_press(void) {
 	gettimeofday(last_press, NULL);
 
+	kill(light_pid, SIGCONT);
+
 	// XXX signal light thread
 }
 
-int keypress_thread(void) {
+int keypress_thread(pid_t _light_pid) {
+	light_pid = _light_pid;
+
 	FILE* fp = fopen(KEYBOARD_FILE, "r");
 	fseek(fp, 0, SEEK_END);
 
diff --git a/src/light_thread.c b/src/light_thread.c
index 1d273a0..20b7bb9 100644
--- a/src/light_thread.c
+++ b/src/light_thread.c
@@ -2,14 +2,13 @@
 
 #include <stdio.h>
 
-#include <stdint.h>
-#include <sys/time.h>
-
 #include "common.h"
 #include "consts.h"
 #include "config.h"
 #include "backlight.h"
 
+static pid_t keypress_pid;
+
 uint64_t time_since_press(void) {
 	struct timeval now;
 
@@ -30,12 +29,24 @@ uint64_t time_since_press(void) {
 	return diff;
 }
 
-int light_thread(void) {
-	while (1) {
-		if (time_since_press() > BACKLIGHT_TIME) backlight_off();
-		else								     backlight_on();
+void handler(int _) {
+	if (time_since_press() > BACKLIGHT_TIME) {
+		backlight_off();
+	} else {
+		backlight_on();
 
-		usleep(THREAD_WAIT);
+		handler(_);
+	}
+}
+
+int light_thread(pid_t _keypress_pid) {
+	keypress_pid = _keypress_pid;
+
+	signal(SIGCONT, handler);
+
+	while (1) {
+		pause();
+//		usleep(THREAD_WAIT);
 	}
 
 	return 0;
diff --git a/src/main.c b/src/main.c
index 4c09563..5c57bbf 100644
--- a/src/main.c
+++ b/src/main.c
@@ -8,8 +8,8 @@
 #include "consts.h"
 #include "config.h"
 
-extern int light_thread(void);
-extern int keypress_thread(void);
+extern int light_thread(pid_t _keypress_pid);
+extern int keypress_thread(pid_t _light_pid);
 
 struct timeval* last_press;
 
@@ -33,6 +33,9 @@ int setup(void) {
 int main(int argc, const char* argv[]) {
 	setup();
 
-	if (fork() == 0) return light_thread();
-	else			 return keypress_thread();
+	pid_t keypress_pid = getpid();
+	pid_t pid = fork();
+
+	if (pid == 0) return light_thread(keypress_pid);
+	else		  return keypress_thread(/*light_*/pid);
 }
-- 
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