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backlight: support to specify percentage of minimum brightness

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Closes #29328.
This commit is contained in:
Yu Watanabe 2023-10-04 21:46:26 +09:00
parent 4f4d7911cd
commit 09ff0aadf9
2 changed files with 32 additions and 17 deletions
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17
man/systemd-backlight@.service.xml
View file

@ -31,16 +31,13 @@
<refsect1>
<title>Description</title>
<para><filename>systemd-backlight@.service</filename> is a service
that restores the display backlight brightness at early boot and
saves it at shutdown. On disk, the backlight brightness is stored
in <filename>/var/lib/systemd/backlight/</filename>. During
loading, if the udev property <option>ID_BACKLIGHT_CLAMP</option> is
not set to false, the brightness is clamped to a value of at
least 1 or 5% of maximum brightness, whichever is greater. This
restriction will be removed when the kernel allows user space to
reliably set a brightness value which does not turn off the
display.</para>
<para><filename>systemd-backlight@.service</filename> is a service that restores the display backlight
brightness at early boot and saves it at shutdown. On disk, the backlight brightness is stored in
<filename>/var/lib/systemd/backlight/</filename>. During loading, if the udev property
<option>ID_BACKLIGHT_CLAMP</option> is not set to false, the brightness is clamped to a value of at least
1 or 5% of maximum brightness, whichever is greater. The percentage can be adjusted by specifying a
percentage (needs to be suffixed with <literal>%</literal>, e.g. <literal>30%</literal>) to the property
<option>ID_BACKLIGHT_CLAMP</option>.</para>
</refsect1>
<refsect1>

32
src/backlight/backlight.c
View file

@ -13,6 +13,7 @@
#include "main-func.h"
#include "mkdir.h"
#include "parse-util.h"
#include "percent-util.h"
#include "pretty-print.h"
#include "process-util.h"
#include "reboot-util.h"
@ -326,7 +327,13 @@ static int get_max_brightness(sd_device *device, unsigned *ret) {
return 0;
}
static int clamp_brightness(sd_device *device, bool saved, unsigned max_brightness, unsigned *brightness) {
static int clamp_brightness(
sd_device *device,
unsigned percent,
bool saved,
unsigned max_brightness,
unsigned *brightness) {
unsigned new_brightness, min_brightness;
const char *subsystem;
int r;
@ -344,7 +351,7 @@ static int clamp_brightness(sd_device *device, bool saved, unsigned max_brightne
return log_device_warning_errno(device, r, "Failed to get device subsystem: %m");
if (streq(subsystem, "backlight"))
min_brightness = MAX(1U, max_brightness/20);
min_brightness = MAX(1U, (unsigned) ((double) max_brightness * percent / 100));
else
min_brightness = 0;
@ -361,26 +368,36 @@ static int clamp_brightness(sd_device *device, bool saved, unsigned max_brightne
return 0;
}
static bool shall_clamp(sd_device *d) {
static bool shall_clamp(sd_device *d, unsigned *ret) {
const char *s;
int r;
assert(d);
assert(ret);
r = sd_device_get_property_value(d, "ID_BACKLIGHT_CLAMP", &s);
if (r < 0) {
if (r != -ENOENT)
log_device_debug_errno(d, r, "Failed to get ID_BACKLIGHT_CLAMP property, ignoring: %m");
*ret = 5; /* defaults to 5% */
return true;
}
r = parse_boolean(s);
if (r >= 0) {
*ret = r ? 5 : 0;
return r;
}
r = parse_percent(s);
if (r < 0) {
log_device_debug_errno(d, r, "Failed to parse ID_BACKLIGHT_CLAMP property, ignoring: %m");
*ret = 5;
return true;
}
return r;
*ret = r;
return true;
}
static int read_brightness(sd_device *device, unsigned max_brightness, unsigned *ret_brightness) {
@ -526,6 +543,7 @@ static int run(int argc, char *argv[]) {
if (streq(argv[1], "load")) {
_cleanup_free_ char *value = NULL;
unsigned percent;
bool clamp;
if (!shall_restore_state())
@ -534,7 +552,7 @@ static int run(int argc, char *argv[]) {
if (validate_device(device) == 0)
return 0;
clamp = shall_clamp(device);
clamp = shall_clamp(device, &percent);
r = read_one_line_file(saved, &value);
if (r < 0 && r != -ENOENT)
@ -548,7 +566,7 @@ static int run(int argc, char *argv[]) {
} else {
log_debug("Using saved brightness %u.", brightness);
if (clamp)
(void) clamp_brightness(device, true, max_brightness, &brightness);
(void) clamp_brightness(device, percent, /* saved = */ true, max_brightness, &brightness);
/* Do not fall back to read current brightness below. */
r = 1;
@ -564,7 +582,7 @@ static int run(int argc, char *argv[]) {
if (r < 0)
return log_device_error_errno(device, r, "Failed to read current brightness: %m");
(void) clamp_brightness(device, false, max_brightness, &brightness);
(void) clamp_brightness(device, percent, /* saved = */ false, max_brightness, &brightness);
}
r = sd_device_set_sysattr_valuef(device, "brightness", "%u", brightness);