backlight.c revision 934ae16baf543af03f3f521277d14524ca772d17
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "libudev.h"
#include "alloc-util.h"
#include "def.h"
#include "escape.h"
#include "fileio.h"
#include "mkdir.h"
#include "parse-util.h"
#include "proc-cmdline.h"
#include "string-util.h"
#include "udev-util.h"
#include "util.h"
static struct udev_device *find_pci_or_platform_parent(struct udev_device *device) {
struct udev_device *parent;
const char *subsystem, *sysname;
assert(device);
parent = udev_device_get_parent(device);
if (!parent)
return NULL;
subsystem = udev_device_get_subsystem(parent);
if (!subsystem)
return NULL;
sysname = udev_device_get_sysname(parent);
if (!sysname)
return NULL;
if (streq(subsystem, "drm")) {
const char *c;
c = startswith(sysname, "card");
if (!c)
return NULL;
c += strspn(c, DIGITS);
if (*c == '-') {
/* A connector DRM device, let's ignore all but LVDS and eDP! */
if (!startswith(c, "-LVDS-") &&
!startswith(c, "-Embedded DisplayPort-"))
return NULL;
}
} else if (streq(subsystem, "pci")) {
const char *value;
value = udev_device_get_sysattr_value(parent, "class");
if (value) {
unsigned long class = 0;
if (safe_atolu(value, &class) < 0) {
log_warning("Cannot parse PCI class %s of device %s:%s.",
value, subsystem, sysname);
return NULL;
}
/* Graphics card */
if (class == 0x30000)
return parent;
}
} else if (streq(subsystem, "platform"))
return parent;
return find_pci_or_platform_parent(parent);
}
static bool same_device(struct udev_device *a, struct udev_device *b) {
assert(a);
assert(b);
if (!streq_ptr(udev_device_get_subsystem(a), udev_device_get_subsystem(b)))
return false;
if (!streq_ptr(udev_device_get_sysname(a), udev_device_get_sysname(b)))
return false;
return true;
}
static bool validate_device(struct udev *udev, struct udev_device *device) {
_cleanup_udev_enumerate_unref_ struct udev_enumerate *enumerate = NULL;
struct udev_list_entry *item = NULL, *first = NULL;
struct udev_device *parent;
const char *v, *subsystem;
int r;
assert(udev);
assert(device);
/* Verify whether we should actually care for a specific
* backlight device. For backlight devices there might be
* multiple ways to access the same control: "firmware"
* (i.e. ACPI), "platform" (i.e. via the machine's EC) and
* "raw" (via the graphics card). In general we should prefer
* "firmware" (i.e. ACPI) or "platform" access over "raw"
* access, in order not to confuse the BIOS/EC, and
* compatibility with possible low-level hotkey handling of
* screen brightness. The kernel will already make sure to
* expose only one of "firmware" and "platform" for the same
* device to userspace. However, we still need to make sure
* that we use "raw" only if no "firmware" or "platform"
* device for the same device exists. */
subsystem = udev_device_get_subsystem(device);
if (!streq_ptr(subsystem, "backlight"))
return true;
v = udev_device_get_sysattr_value(device, "type");
if (!streq_ptr(v, "raw"))
return true;
parent = find_pci_or_platform_parent(device);
if (!parent)
return true;
subsystem = udev_device_get_subsystem(parent);
if (!subsystem)
return true;
enumerate = udev_enumerate_new(udev);
if (!enumerate)
return true;
r = udev_enumerate_add_match_subsystem(enumerate, "backlight");
if (r < 0)
return true;
r = udev_enumerate_scan_devices(enumerate);
if (r < 0)
return true;
first = udev_enumerate_get_list_entry(enumerate);
udev_list_entry_foreach(item, first) {
_cleanup_udev_device_unref_ struct udev_device *other;
struct udev_device *other_parent;
const char *other_subsystem;
other = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
if (!other)
return true;
if (same_device(device, other))
continue;
v = udev_device_get_sysattr_value(other, "type");
if (!streq_ptr(v, "platform") && !streq_ptr(v, "firmware"))
continue;
/* OK, so there's another backlight device, and it's a
* platform or firmware device, so, let's see if we
* can verify it belongs to the same device as
* ours. */
other_parent = find_pci_or_platform_parent(other);
if (!other_parent)
continue;
if (same_device(parent, other_parent)) {
/* Both have the same PCI parent, that means
* we are out. */
log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
udev_device_get_sysname(device),
udev_device_get_sysname(other));
return false;
}
other_subsystem = udev_device_get_subsystem(other_parent);
if (streq_ptr(other_subsystem, "platform") && streq_ptr(subsystem, "pci")) {
/* The other is connected to the platform bus
* and we are a PCI device, that also means we
* are out. */
log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
udev_device_get_sysname(device),
udev_device_get_sysname(other));
return false;
}
}
return true;
}
static unsigned get_max_brightness(struct udev_device *device) {
int r;
const char *max_brightness_str;
unsigned max_brightness;
max_brightness_str = udev_device_get_sysattr_value(device, "max_brightness");
if (!max_brightness_str) {
log_warning("Failed to read 'max_brightness' attribute.");
return 0;
}
r = safe_atou(max_brightness_str, &max_brightness);
if (r < 0) {
log_warning_errno(r, "Failed to parse 'max_brightness' \"%s\": %m", max_brightness_str);
return 0;
}
if (max_brightness <= 0) {
log_warning("Maximum brightness is 0, ignoring device.");
return 0;
}
return max_brightness;
}
/* Some systems turn the backlight all the way off at the lowest levels.
* clamp_brightness clamps the saved brightness to at least 1 or 5% of
* max_brightness in case of 'backlight' subsystem. This avoids preserving
* an unreadably dim screen, which would otherwise force the user to
* disable state restoration. */
static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
int r;
unsigned brightness, new_brightness, min_brightness;
const char *subsystem;
r = safe_atou(*value, &brightness);
if (r < 0) {
log_warning_errno(r, "Failed to parse brightness \"%s\": %m", *value);
return;
}
subsystem = udev_device_get_subsystem(device);
if (streq_ptr(subsystem, "backlight"))
min_brightness = MAX(1U, max_brightness/20);
else
min_brightness = 0;
new_brightness = CLAMP(brightness, min_brightness, max_brightness);
if (new_brightness != brightness) {
char *old_value = *value;
r = asprintf(value, "%u", new_brightness);
if (r < 0) {
log_oom();
return;
}
log_info("Saved brightness %s %s to %s.", old_value,
new_brightness > brightness ?
"too low; increasing" : "too high; decreasing",
*value);
free(old_value);
}
}
int main(int argc, char *argv[]) {
_cleanup_udev_unref_ struct udev *udev = NULL;
_cleanup_udev_device_unref_ struct udev_device *device = NULL;
_cleanup_free_ char *saved = NULL, *ss = NULL, *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
const char *sysname, *path_id;
unsigned max_brightness;
int r;
if (argc != 3) {
log_error("This program requires two arguments.");
return EXIT_FAILURE;
}
log_set_target(LOG_TARGET_AUTO);
log_parse_environment();
log_open();
umask(0022);
r = mkdir_p("/var/lib/systemd/backlight", 0755);
if (r < 0) {
log_error_errno(r, "Failed to create backlight directory /var/lib/systemd/backlight: %m");
return EXIT_FAILURE;
}
udev = udev_new();
if (!udev) {
log_oom();
return EXIT_FAILURE;
}
sysname = strchr(argv[2], ':');
if (!sysname) {
log_error("Requires a subsystem and sysname pair specifying a backlight device.");
return EXIT_FAILURE;
}
ss = strndup(argv[2], sysname - argv[2]);
if (!ss) {
log_oom();
return EXIT_FAILURE;
}
sysname++;
if (!streq(ss, "backlight") && !streq(ss, "leds")) {
log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
return EXIT_FAILURE;
}
errno = 0;
device = udev_device_new_from_subsystem_sysname(udev, ss, sysname);
if (!device) {
if (errno != 0)
log_error_errno(errno, "Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
else
log_oom();
return EXIT_FAILURE;
}
/* If max_brightness is 0, then there is no actual backlight
* device. This happens on desktops with Asus mainboards
* that load the eeepc-wmi module.
*/
max_brightness = get_max_brightness(device);
if (max_brightness == 0)
return EXIT_SUCCESS;
escaped_ss = cescape(ss);
if (!escaped_ss) {
log_oom();
return EXIT_FAILURE;
}
escaped_sysname = cescape(sysname);
if (!escaped_sysname) {
log_oom();
return EXIT_FAILURE;
}
path_id = udev_device_get_property_value(device, "ID_PATH");
if (path_id) {
escaped_path_id = cescape(path_id);
if (!escaped_path_id) {
log_oom();
return EXIT_FAILURE;
}
saved = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname, NULL);
} else
saved = strjoin("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname, NULL);
if (!saved) {
log_oom();
return EXIT_FAILURE;
}
/* If there are multiple conflicting backlight devices, then
* their probing at boot-time might happen in any order. This
* means the validity checking of the device then is not
* reliable, since it might not see other devices conflicting
* with a specific backlight. To deal with this, we will
* actively delete backlight state files at shutdown (where
* device probing should be complete), so that the validity
* check at boot time doesn't have to be reliable. */
if (streq(argv[1], "load")) {
_cleanup_free_ char *value = NULL;
const char *clamp;
if (shall_restore_state() == 0)
return EXIT_SUCCESS;
if (!validate_device(udev, device))
return EXIT_SUCCESS;
r = read_one_line_file(saved, &value);
if (r < 0) {
if (r == -ENOENT)
return EXIT_SUCCESS;
log_error_errno(r, "Failed to read %s: %m", saved);
return EXIT_FAILURE;
}
clamp = udev_device_get_property_value(device, "ID_BACKLIGHT_CLAMP");
if (!clamp || parse_boolean(clamp) != 0) /* default to clamping */
clamp_brightness(device, &value, max_brightness);
r = udev_device_set_sysattr_value(device, "brightness", value);
if (r < 0) {
log_error_errno(r, "Failed to write system 'brightness' attribute: %m");
return EXIT_FAILURE;
}
} else if (streq(argv[1], "save")) {
const char *value;
if (!validate_device(udev, device)) {
unlink(saved);
return EXIT_SUCCESS;
}
value = udev_device_get_sysattr_value(device, "brightness");
if (!value) {
log_error("Failed to read system 'brightness' attribute");
return EXIT_FAILURE;
}
r = write_string_file(saved, value, WRITE_STRING_FILE_CREATE);
if (r < 0) {
log_error_errno(r, "Failed to write %s: %m", saved);
return EXIT_FAILURE;
}
} else {
log_error("Unknown verb %s.", argv[1]);
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}