desktop-tools/brightness.c

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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.
*
*/
// Sources: ddcciv1r1.pdf, i2c-dev.c in Linux, ddccontrol source code,
// http://www.boichat.ch/nicolas/ddcci/specs.html was also helpful
// 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
// Undo some dwm Makefile damage and import my everything-library
#include "config.h"
#undef PROGRAM_NAME
#define PROGRAM_NAME "brightness"
#include "liberty/liberty.c"
#include <sys/ioctl.h>
#include <dirent.h>
#include <linux/i2c-dev.h>
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#ifndef I2C_FUNC_I2C
// Fuck you, openSUSE, for fucking up the previous file, see e.g.
// https://github.com/solettaproject/soletta/commit/427f47f
#include <linux/i2c.h>
#endif
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
log_message_custom (void *user_data, const char *quote, const char *fmt,
va_list ap)
{
(void) user_data;
FILE *stream = stdout;
fprintf (stream, PROGRAM_NAME ": ");
fputs (quote, stream);
vfprintf (stream, fmt, ap);
fputs ("\n", stream);
}
static void
wait_ms (long ms)
{
struct timespec ts = { 0, ms * 1000 * 1000 };
nanosleep (&ts, NULL);
}
static bool
xstrtol (const char *s, long *out)
{
char *end;
errno = 0;
*out = strtol (s, &end, 10);
return errno == 0 && !*end && end != s;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#define DDC_LENGTH_XOR 0x80
enum
{
DDC_ADDRESS_HOST = 0x50, ///< Bus master's base address
DDC_ADDRESS_DISPLAY = 0x6E ///< The display's base address
};
enum { I2C_WRITE, I2C_READ };
enum
{
DDC_GET_VCP_FEATURE = 0x01, ///< Request info about a feature
DDC_GET_VCP_FEATURE_REPLY = 0x02, ///< Feature info response
DDC_SET_VCP_FEATURE = 0x03 ///< Set or activate a feature
};
enum
{
VCP_BRIGHTNESS = 0x10, ///< Standard VCP opcode for brightness
VCP_CONTRAST = 0x12 ///< Standard VCP opcode for contrast
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
check_edid (int fd, struct error **e)
{
uint8_t edid_req[] = { 0x00 };
uint8_t buf[8] = "";
struct i2c_msg bufs[] =
{
{ .addr = 0x50, .flags = 0,
.len = 1, .buf = edid_req },
{ .addr = 0x50, .flags = I2C_M_RD,
.len = sizeof buf, .buf = buf },
};
struct i2c_rdwr_ioctl_data data;
data.msgs = bufs;
data.nmsgs = 2;
if (ioctl (fd, I2C_RDWR, &data) < 0)
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return error_set (e, "%s: %s", "ioctl", strerror (errno));
if (memcmp ("\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00", buf, sizeof buf))
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return error_set (e, "invalid EDID");
return true;
}
static bool
is_a_display (int fd, struct error **e)
{
struct stat st;
if (fstat (fd, &st) < 0)
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return error_set (e, "%s: %s", "fstat", strerror (errno));
unsigned long funcs;
if (!(st.st_mode & S_IFCHR)
|| ioctl (fd, I2C_FUNCS, &funcs) < 0
|| !(funcs & I2C_FUNC_I2C))
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return error_set (e, "not an I2C device");
return check_edid (fd, e);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
ddc_send (int fd, unsigned command, void *args, size_t args_len,
struct error **e)
{
struct str buf;
str_init (&buf);
str_pack_u8 (&buf, DDC_ADDRESS_HOST | I2C_READ);
str_pack_u8 (&buf, DDC_LENGTH_XOR | (args_len + 1));
str_pack_u8 (&buf, command);
str_append_data (&buf, args, args_len);
unsigned xor = DDC_ADDRESS_DISPLAY;
for (size_t i = 0; i < buf.len; i++)
xor ^= buf.str[i];
str_pack_u8 (&buf, xor);
struct i2c_msg msg =
{
// The driver unshifts it back
.addr = DDC_ADDRESS_DISPLAY >> 1, .flags = 0,
.len = buf.len, .buf = (uint8_t *) buf.str,
};
struct i2c_rdwr_ioctl_data data;
data.msgs = &msg;
data.nmsgs = 1;
bool failed = ioctl (fd, I2C_RDWR, &data) < 0;
str_free (&buf);
if (failed)
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return error_set (e, "%s: %s", "ioctl", strerror (errno));
return true;
}
static bool
ddc_read (int fd, unsigned *command, void *out_buf, size_t *n_read,
struct error **e)
{
uint8_t buf[128] = "";
struct i2c_msg msg =
{
// The driver unshifts it back
.addr = DDC_ADDRESS_DISPLAY >> 1, .flags = I2C_M_RD,
.len = sizeof buf, .buf = buf,
};
struct i2c_rdwr_ioctl_data data;
data.msgs = &msg;
data.nmsgs = 1;
if (ioctl (fd, I2C_RDWR, &data) < 0)
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return error_set (e, "%s: %s", "ioctl", strerror (errno));
struct msg_unpacker unpacker;
msg_unpacker_init (&unpacker, buf, sizeof buf);
uint8_t sender, length, cmd;
(void) msg_unpacker_u8 (&unpacker, &sender);
(void) msg_unpacker_u8 (&unpacker, &length);
(void) msg_unpacker_u8 (&unpacker, &cmd);
if (sender != (DDC_ADDRESS_DISPLAY | I2C_WRITE) || !(length & 0x80))
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return error_set (e, "invalid response");
if (!(length ^= 0x80))
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return error_set (e, "NULL response");
// TODO: also check the checksum
*command = cmd;
memcpy (out_buf, unpacker.data + unpacker.offset, (*n_read = length - 1));
return true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
set_brightness (int fd, long diff, struct error **e)
{
uint8_t get_req[] = { VCP_BRIGHTNESS };
if (!ddc_send (fd, DDC_GET_VCP_FEATURE, get_req, sizeof get_req, e))
return false;
wait_ms (40);
unsigned command = 0;
uint8_t buf[128] = "";
size_t len = 0;
if (!ddc_read (fd, &command, buf, &len, e))
return false;
if (command != DDC_GET_VCP_FEATURE_REPLY || len != 7)
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return error_set (e, "invalid response");
struct msg_unpacker unpacker;
msg_unpacker_init (&unpacker, buf, len);
uint8_t result; msg_unpacker_u8 (&unpacker, &result);
uint8_t vcp_opcode; msg_unpacker_u8 (&unpacker, &vcp_opcode);
uint8_t type; msg_unpacker_u8 (&unpacker, &type);
int16_t max; msg_unpacker_i16 (&unpacker, &max);
int16_t cur; msg_unpacker_i16 (&unpacker, &cur);
if (result == 0x01)
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return error_set (e, "error reported by monitor");
if (result != 0x00
|| vcp_opcode != VCP_BRIGHTNESS)
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return error_set (e, "invalid response");
// These are unsigned but usually just one byte long
if (max < 0 || cur < 0)
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return error_set (e, "capability range overflow");
int16_t req = (cur * 100 + diff * max + 50) / 100;
if (req > max) req = max;
if (req < 0) 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 / 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)
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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)
{
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return error_set (e,
"%s: %s: %s", "brightness", "openat", strerror (errno));
}
struct str s;
str_init (&s);
str_append_printf (&s, "%ld", req);
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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;
}