alight/alight.c at main · httpsworldview/alight · GitHub

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* SPDX-License-Identifier: GPL-3.0-or-later

#include <dirent.h>

#include <err.h>

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#ifndef SYSFS

#define SYSFS "/sys/class/backlight"

#endif

enum { NAME_LEN = 256, TYPE_LEN = 32, LINE_LEN = 64 };

struct light {

char name[NAME_LEN], type[TYPE_LEN];

long now, max;

};

static int fail(int error) {

errno = error ? error : EIO;

return -1;

}

static int usage(FILE *out, int code) {

fputs("usage: alight [-d DEVICE] [N|+N|-N]\n"

" alight -l\n"

" alight -h\n", out);

return code;

}

static long clamp(long value, long min, long max) {

return value < min ? min : value > max ? max : value;

}

static long percent(long raw, long max) {

return (long)((long double)clamp(raw, 0, max) * 100 / max + 0.5L);

}

static long raw_percent(long value, long max) {

return max / 100 * value + (max % 100 * value + 50) / 100;

}

static long target_raw(const struct light *light, long adjustment,

char operation) {

long max = light->max;

long now = clamp(light->now, 0, max);

long delta = raw_percent(adjustment < 0 ? -adjustment : adjustment, max);

if (operation != '+' && operation != '-')

return delta;

if (adjustment > 0)

return delta > max - now ? max : now + delta;

return delta > now ? 0 : now - delta;

}

static int valid_name(const char *name) {

return *name && strcmp(name, ".") && strcmp(name, "..") &&

strlen(name) < NAME_LEN && !strchr(name, '/');

}

static FILE *open_attr(const char *dev, const char *attr, const char *mode) {

char path[sizeof SYSFS + NAME_LEN + sizeof "/max_brightness"];

snprintf(path, sizeof path, "%s/%s/%s", SYSFS, dev, attr);

return fopen(path, mode);

}

static int close_as(FILE *file, int error) {

if (fclose(file) && !error)

error = errno ? errno : EIO;

return error ? fail(error) : 0;

}

static int read_attr(const char *dev, const char *attr, char *buf, int len) {

FILE *file = open_attr(dev, attr, "r");

char *newline;

int error = 0;

if (!file)

return -1;

errno = 0;

if (!fgets(buf, len, file))

error = ferror(file) ? (errno ? errno : EIO) : EINVAL;

else if ((newline = strchr(buf, '\n')))

*newline = 0;

else if (!feof(file))

error = ENAMETOOLONG;

return close_as(file, error);

}

static int parse_number(const char *text, long *value) {

char *end;

errno = 0;

if ((unsigned char)*text <= ' ')

return fail(EINVAL);

*value = strtol(text, &end, 10);

return errno || end == text || *end ? fail(errno ? errno : EINVAL) : 0;

}

static int read_number(const char *dev, const char *attr, long *value) {

char buf[LINE_LEN];

if (read_attr(dev, attr, buf, sizeof buf) || parse_number(buf, value))

return -1;

return *value < 0 ? fail(EINVAL) : 0;

}

static int write_brightness(const char *dev, long value) {

FILE *file = open_attr(dev, "brightness", "w");

int error = 0;

if (!file)

return -1;

errno = 0;

if (fprintf(file, "%ld\n", value) < 0)

error = errno ? errno : EIO;

return close_as(file, error);

}

static int type_rank(const char *type) {

return !strcmp(type, "firmware") ? 0 :

!strcmp(type, "platform") ? 1 : !strcmp(type, "raw") ? 2 : 3;

}

static int load_light(struct light *light, const char *name) {

if (!valid_name(name))

return fail(EINVAL);

strcpy(light->name, name);

if (read_number(name, "max_brightness", &light->max))

return -1;

if (light->max <= 0)

return fail(EINVAL);

if (read_number(name, "brightness", &light->now))

return -1;

if (read_attr(name, "type", light->type, sizeof light->type))

strcpy(light->type, "unknown");

return 0;

}

static int better_light(const struct light *a, const struct light *b) {

int a_rank = type_rank(a->type), b_rank = type_rank(b->type);

return a_rank < b_rank ||

(a_rank == b_rank && strcmp(a->name, b->name) < 0);

}

static void scan_lights(struct light *best) {

DIR *dir = opendir(SYSFS);

struct dirent *entry;

struct light light;

int found = 0;

if (!dir)

err(1, "%s", SYSFS);

for (errno = 0; (entry = readdir(dir)); errno = 0) {

if (load_light(&light, entry->d_name))

continue;

if (!best)

printf("%s\t%ld%%\t%ld/%ld\t%s\n", light.name,

percent(light.now, light.max), light.now, light.max,

light.type);

else if (!found || better_light(&light, best))

*best = light;

found = 1;

}

if (errno || closedir(dir))

err(1, "%s", SYSFS);

if (!found)

errx(1, "no backlight in %s", SYSFS);

}

int main(int argc, char **argv) {

struct light light;

long adjustment = 0;

const char *device = getenv("ALIGHT_DEVICE"), *value_arg = NULL;

int list = 0, device_arg = 0;

for (int i = 1; i < argc; i++) {

const char *arg = argv[i];

char option = *arg == '-' && arg[1] && !arg[2] ? arg[1] : 0;

if (option == 'h')

return usage(stdout, 0);

if (option == 'l')

list = 1;

else if (option == 'd') {

if (++i == argc)

return usage(stderr, 2);

device = argv[i];

device_arg = 1;

} else if (value_arg)

return usage(stderr, 2);

else

value_arg = arg;

}

if (list) {

if (value_arg || device_arg)

return usage(stderr, 2);

scan_lights(NULL);

return 0;

}

if (value_arg && parse_number(value_arg, &adjustment))

return usage(stderr, 2);

adjustment = clamp(adjustment, -100, 100);

if (!device_arg && (!device || !*device))

scan_lights(&light);

else if (load_light(&light, device))

err(1, "%s", device);

if (!value_arg)

printf("%ld\n", percent(light.now, light.max));

else if (write_brightness(

light.name, target_raw(&light, adjustment, *value_arg)))

err(1, "%s/brightness", light.name);

return 0;

}

alight/alight.c at main · httpsworldview/alight · GitHub

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