From fa3c17aa4a11829d543cb7c0eaa752b72fed2051 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sun, 16 Dec 2018 17:04:44 +0100
Subject: [PATCH] module/battery: use libudev to monitor for battery changes

This allows us to detect plug/unplug events immediately, instead of
having to wait for the next poll event.

Unfortunately, capacity changes do not appear to generate events :(
---
 CMakeLists.txt            |  4 ++++
 modules/battery/battery.c | 47 +++++++++++++++++++++++++++++++++------
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 11ea46e..48b7a48 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,7 @@ pkg_check_modules(CAIRO REQUIRED cairo cairo-xcb)        # Core
 pkg_check_modules(YAML REQUIRED yaml-0.1)                # Core (configuration)
 
 pkg_check_modules(JSON REQUIRED json-c)                  # Module/i3
+pkg_check_modules(UDEV REQUIRED libudev)                 # Module/battery
 
 add_executable(f00bar
   bar.c bar.h
@@ -47,6 +48,7 @@ target_compile_options(f00bar PRIVATE
   ${CAIRO_CFLAGS_OTHER}
   ${YAML_CFLAGS_OTHER}
   ${JSON_CFLAGS_OTHER}
+  ${UDEV_CFLAGS_OTHER}
   )
 
 target_include_directories(f00bar PRIVATE
@@ -54,6 +56,7 @@ target_include_directories(f00bar PRIVATE
   ${CAIRO_INCLUDE_DIRS}
   ${YAML_INCLUDE_DIRS}
   ${JSON_INCLUDE_DIRS}
+  ${UDEV_INCLUDE_DIRS}
   )
 
 target_link_libraries(f00bar
@@ -62,4 +65,5 @@ target_link_libraries(f00bar
   ${CAIRO_LIBRARIES}
   ${YAML_LIBRARIES}
   ${JSON_LIBRARIES}
+  ${UDEV_LIBRARIES}
   )
diff --git a/modules/battery/battery.c b/modules/battery/battery.c
index ad62164..f6b9675 100644
--- a/modules/battery/battery.c
+++ b/modules/battery/battery.c
@@ -11,6 +11,8 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 
+#include <libudev.h>
+
 #include "../../bar.h"
 
 enum state { STATE_FULL, STATE_CHARGING, STATE_DISCHARGING };
@@ -183,7 +185,41 @@ run(struct module_run_context *ctx)
     int power_fd = openat(base_dir_fd, "power_now", O_RDONLY);
     assert(power_fd != -1);
 
-    do {
+    struct udev *udev = udev_new();
+    assert(udev != NULL);
+
+    struct udev_monitor *mon = udev_monitor_new_from_netlink(udev, "udev");
+    assert(mon != NULL);
+
+    int r = udev_monitor_filter_add_match_subsystem_devtype(mon, "power_supply", NULL);
+    assert(r == 0);
+    r = udev_monitor_enable_receiving(mon);
+    assert(r == 0);
+
+    bool first = true;
+    while (true) {
+        if (!first) {
+            struct pollfd fds[] = {
+                {.fd = ctx->abort_fd, .events = POLLIN},
+                {.fd = udev_monitor_get_fd(mon), .events = POLLIN},
+            };
+            poll(fds, 2, m->poll_interval * 1000);
+
+            if (fds[0].revents & POLLIN)
+                break;
+
+            if (fds[1].revents & POLLIN) {
+                struct udev_device *dev = udev_monitor_receive_device(mon);
+                bool is_us = strcmp(udev_device_get_sysname(dev), m->battery) == 0;
+
+                udev_device_unref(dev);
+
+                if (!is_us)
+                    continue;
+            }
+        } else
+            first = false;
+
         const char *status = readline_from_fd(status_fd);
         if (strcmp(status, "Full") == 0)
             m->state = STATE_FULL;
@@ -207,13 +243,10 @@ run(struct module_run_context *ctx)
         //       m->capacity, m->energy, m->power);
 
         bar->refresh(bar);
+    }
 
-        struct pollfd fds[] = {{.fd = ctx->abort_fd, .events = POLLIN}};
-        poll(fds, 1, m->poll_interval * 1000);
-
-        if (fds[0].revents & POLLIN)
-            break;
-    } while (true);
+    udev_monitor_unref(mon);
+    udev_unref(udev);
 
     close(power_fd);
     close(energy_fd);