LED subsystem supports POLLPRI on "brightness_hw_changed" sysfs file
of LED class devices. This tool demonstrates how to use the feature.
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
---
tools/leds/Makefile | 4 +-
tools/leds/led_hw_brightness_mon.c | 84 ++++++++++++++++++++++++++++++++++++++
2 files changed, 86 insertions(+), 2 deletions(-)
create mode 100644 tools/leds/led_hw_brightness_mon.c
diff --git a/tools/leds/Makefile b/tools/leds/Makefile
index c03a79e..078b666 100644
--- a/tools/leds/Makefile
+++ b/tools/leds/Makefile
@@ -3,11 +3,11 @@
CC = $(CROSS_COMPILE)gcc
CFLAGS = -Wall -Wextra -g -I../../include/uapi
-all: uledmon
+all: uledmon led_hw_brightness_mon
%: %.c
$(CC) $(CFLAGS) -o $@ $^
clean:
- $(RM) uledmon
+ $(RM) uledmon led_hw_brightness_mon
.PHONY: all clean
diff --git a/tools/leds/led_hw_brightness_mon.c b/tools/leds/led_hw_brightness_mon.c
new file mode 100644
index 0000000..1a97064
--- /dev/null
+++ b/tools/leds/led_hw_brightness_mon.c
@@ -0,0 +1,84 @@
+/*
+ * led_hw_brightness_mon.c
+ *
+ * This program monitors LED brightness level changes having its origin
+ * in hardware/firmware, i.e. outside of kernel control.
+ * A timestamp and brightness value is printed each time the brightness changes.
+ *
+ * Usage: led_notify_mon <device-name>
+ *
+ * <device-name> is the name of the LED class device to be monitored. Pressing
+ * CTRL+C will exit.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <linux/uleds.h>
+
+int main(int argc, char const *argv[])
+{
+ int fd, ret;
+ char brightness_file_path[LED_MAX_NAME_SIZE + 11];
+ struct pollfd pollfd;
+ struct timespec ts;
+ char buf[11];
+
+ if (argc != 2) {
+ fprintf(stderr, "Requires <device-name> argument\n");
+ return 1;
+ }
+
+ snprintf(brightness_file_path, LED_MAX_NAME_SIZE,
+ "/sys/class/leds/%s/brightness_hw_changed", argv[1]);
+
+ fd = open(brightness_file_path, O_RDONLY);
+ if (fd == -1) {
+ printf("Failed to open %s file\n", brightness_file_path);
+ return 1;
+ }
+
+ /*
+ * read may fail if no hw brightness change has occurred so far,
+ * but it is required to avoid spurious poll notifications in
+ * the opposite case.
+ */
+ read(fd, buf, sizeof(buf));
+
+ pollfd.fd = fd;
+ pollfd.events = POLLPRI;
+
+ while (1) {
+ ret = poll(&pollfd, 1, -1);
+ if (ret == -1) {
+ printf("Failed to poll %s file (%d)\n",
+ brightness_file_path, ret);
+ ret = 1;
+ break;
+ }
+
+ clock_gettime(CLOCK_MONOTONIC, &ts);
+
+ ret = read(fd, buf, sizeof(buf));
+ if (ret < 0)
+ break;
+
+ ret = lseek(pollfd.fd, 0, SEEK_SET);
+ if (ret < 0) {
+ printf("lseek failed (%d)\n", ret);
+ break;
+ }
+
+ printf("[%ld.%09ld] %d\n", ts.tv_sec, ts.tv_nsec, atoi(buf));
+ }
+
+ close(fd);
+
+ return ret;
+}
--
2.1.4
