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/*
* brightness.c: set display brightness via DDC/CI - Linux only
*
* Copyright (c) 2015, Přemysl Janouch <p.janouch@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
// This makes openat() available even though I set _POSIX_C_SOURCE and
// _XOPEN_SOURCE to a version of POSIX older than 2008
#define _GNU_SOURCE
#include "config.h"
#undef PROGRAM_NAME
#define PROGRAM_NAME "brightness"
#include "liberty/liberty.c"
#include "ddc-ci.c"
#include <dirent.h>
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
xstrtol (const char *s, long *out)
{
char *end;
errno = 0;
*out = strtol (s, &end, 10);
return errno == 0 && !*end && end != s;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
set_brightness (int fd, long diff, struct error **e)
{
struct vcp_feature_readout readout = {};
if (!vcp_get_feature (fd, VCP_BRIGHTNESS, &readout, e))
return false;
int16_t req = (readout.cur * 100 + diff * readout.max + 50) / 100;
req = MIN (req, readout.max);
req = MAX (req, 0);
uint8_t set_req[] = { VCP_BRIGHTNESS, req >> 8, req };
if (!ddc_send (fd, DDC_SET_VCP_FEATURE, set_req, sizeof set_req, e))
return false;
wait_ms (50);
printf ("brightness set to %.2f%%\n", 100. * req / readout.max);
return true;
}
static void
i2c (long diff)
{
DIR *dev = opendir ("/dev");
if (!dev)
{
print_error ("cannot access %s: %s: %s",
"/dev", "opendir", strerror (errno));
return;
}
struct dirent *entry;
while ((entry = readdir (dev)))
{
if (strncmp (entry->d_name, "i2c-", 4))
continue;
printf ("Trying %s... ", entry->d_name);
int fd = openat (dirfd (dev), entry->d_name, O_RDONLY);
if (fd < 0)
{
print_error ("%s: %s", "openat", strerror (errno));
continue;
}
struct error *e = NULL;
if (!is_a_display (fd, &e)
|| !set_brightness (fd, diff, &e))
{
printf ("%s\n", e->message);
error_free (e);
}
close (fd);
}
closedir (dev);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static long
read_value (int dir, const char *filename, struct error **e)
{
int fd = openat (dir, filename, O_RDONLY);
if (fd < 0)
{
error_set (e, "%s: %s: %s", filename, "openat", strerror (errno));
return -1;
}
FILE *fp = fdopen (fd, "r");
if (!fp)
{
error_set (e, "%s: %s: %s", filename, "fdopen", strerror (errno));
close (fd);
return -1;
}
struct str s;
str_init (&s);
long value;
if (!read_line (fp, &s)
|| !xstrtol (s.str, &value))
{
value = -1;
error_set (e, "%s: %s", filename, "failed reading an integer value");
}
str_free (&s);
fclose (fp);
return value;
}
static bool
set_backlight (int dir, long diff, struct error **e)
{
long cur, max;
struct error *error = NULL;
if ((cur = read_value (dir, "brightness", &error), error)
|| (max = read_value (dir, "max_brightness", &error), error))
{
error_propagate (e, error);
return false;
}
if (cur < 0 || max < 0)
return error_set (e, "invalid range or current value");
long req = (cur * 100 + diff * max + 50) / 100;
if (req > max) req = max;
if (req < 0) req = 0;
int fd = openat (dir, "brightness", O_WRONLY);
if (fd < 0)
{
return error_set (e,
"%s: %s: %s", "brightness", "openat", strerror (errno));
}
struct str s;
str_init (&s);
str_append_printf (&s, "%ld", req);
bool result = write (fd, s.str, s.len) == (ssize_t) s.len;
str_free (&s);
if (!result)
error_set (e, "%s: %s: %s", "brightness", "write", strerror (errno));
close (fd);
printf ("brightness set to %.2f%%\n", 100. * req / max);
return result;
}
static void
backlight (long diff)
{
DIR *backlight = opendir ("/sys/class/backlight");
if (!backlight)
{
print_error ("cannot access %s: %s: %s",
"/sys/class/backlight", "opendir", strerror (errno));
return;
}
struct dirent *entry;
while ((entry = readdir (backlight)))
{
const char *device_name = entry->d_name;
if (device_name[0] == '.')
continue;
printf ("Trying %s... ", entry->d_name);
int dir = openat (dirfd (backlight), entry->d_name, O_RDONLY);
if (dir < 0)
{
print_error ("%s: %s", "openat", strerror (errno));
continue;
}
struct error *e = NULL;
if (!set_backlight (dir, diff, &e))
{
printf ("%s\n", e->message);
error_free (e);
}
close (dir);
}
closedir (backlight);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
int
main (int argc, char *argv[])
{
g_log_message_real = log_message_custom;
long diff = 0;
if (argc > 1 && !xstrtol (argv[1], &diff))
{
printf ("Usage: %s <percentage diff>\n", argv[0]);
exit (EXIT_FAILURE);
}
i2c (diff);
backlight (diff);
return 0;
}
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