linux-kernel - Re: [PATCH/RFC v2] tools/leds: Add led_notify_mon program for monitoring brightness changes

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Date:   Wed, 9 Nov 2016 12:50:05 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        linux-leds@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC v2] tools/leds: Add led_notify_mon program for
 monitoring brightness changes

Hi,

On 08-11-16 12:36, Jacek Anaszewski wrote:
> LED subsystem supports POLLPRI on "brightness" sysfs file of LED
> class devices. This tool demonstrates how to use the feature.
>
> Signed-off-by: Jacek Anaszewski <j.anaszewski@...sung.com>
> Cc: Hans de Goede <hdegoede@...hat.com>

Thank you.

Patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans

> ---
> Changes since v1:
> - added lseek which fixes non-blocking poll() behaviour
>
>  tools/leds/Makefile         |  4 +--
>  tools/leds/led_notify_mon.c | 83 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 85 insertions(+), 2 deletions(-)
>  create mode 100644 tools/leds/led_notify_mon.c
>
> diff --git a/tools/leds/Makefile b/tools/leds/Makefile
> index c03a79e..0fa948a 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_notify_mon
>  %: %.c
>  	$(CC) $(CFLAGS) -o $@ $^
>
>  clean:
> -	$(RM) uledmon
> +	$(RM) uledmon led_notify_mon
>
>  .PHONY: all clean
> diff --git a/tools/leds/led_notify_mon.c b/tools/leds/led_notify_mon.c
> new file mode 100644
> index 0000000..8b6e6f9
> --- /dev/null
> +++ b/tools/leds/led_notify_mon.c
> @@ -0,0 +1,83 @@
> +/*
> + * led_notify_mon.c
> + *
> + * This program monitors LED brightness change notifications,
> + * either having its origin in the hardware or in the software.
> + * 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 <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[LEDS_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, LEDS_MAX_NAME_SIZE,
> +		 "/sys/class/leds/%s/brightness", argv[1]);
> +
> +	fd = open(brightness_file_path, O_RDONLY);
> +	if (fd == -1) {
> +		printf("Failed to open %s file\n", brightness_file_path);
> +		return 1;
> +	}
> +
> +	ret = read(fd, buf, sizeof(buf));
> +	if (ret < 0) {
> +		printf("Failed to read %s file\n", brightness_file_path);
> +		goto err_read;
> +	}
> +
> +	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));
> +	}
> +
> +err_read:
> +	close(fd);
> +
> +	return ret;
> +}
>