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systemd/src/backlight/backlight.c
Yu Watanabe 9990552f9a backlight: fix detection of multiple graphic cards 
Follow-up for e0504dd011.

Hopefully, devices in PCI subsystem have some properties, thus have
their udev database file. But, that may not be true. Here, we only read
sysattrs of enumerated devices, hence it is not necessary to check if
the device is initialized or not.
2024-04-04 21:29:57 +01:00

674 lines
24 KiB
C
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "sd-device.h"
#include "alloc-util.h"
#include "device-util.h"
#include "escape.h"
#include "fileio.h"
#include "main-func.h"
#include "parse-util.h"
#include "percent-util.h"
#include "pretty-print.h"
#include "process-util.h"
#include "reboot-util.h"
#include "string-util.h"
#include "strv.h"
#include "terminal-util.h"
#include "verbs.h"
#define PCI_CLASS_GRAPHICS_CARD 0x30000
static int help(void) {
_cleanup_free_ char *link = NULL;
int r;
r = terminal_urlify_man("systemd-backlight", "8", &link);
if (r < 0)
return log_oom();
printf("%s save [backlight|leds]:DEVICE\n"
"%s load [backlight|leds]:DEVICE\n"
"\n%sSave and restore backlight brightness at shutdown and boot.%s\n\n"
" save Save current brightness\n"
" load Set brightness to be the previously saved value\n"
"\nSee the %s for details.\n",
program_invocation_short_name,
program_invocation_short_name,
ansi_highlight(),
ansi_normal(),
link);
return 0;
}
static int has_multiple_graphics_cards(void) {
_cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
bool found = false;
int r;
r = sd_device_enumerator_new(&e);
if (r < 0)
return r;
r = sd_device_enumerator_allow_uninitialized(e);
if (r < 0)
return r;
r = sd_device_enumerator_add_match_subsystem(e, "pci", /* match = */ true);
if (r < 0)
return r;
/* class is an unsigned number, let's validate the value later. */
r = sd_device_enumerator_add_match_sysattr(e, "class", NULL, /* match = */ true);
if (r < 0)
return r;
FOREACH_DEVICE(e, dev) {
const char *s;
unsigned long c;
if (sd_device_get_sysattr_value(dev, "class", &s) < 0)
continue;
if (safe_atolu(s, &c) < 0)
continue;
if (c != PCI_CLASS_GRAPHICS_CARD)
continue;
if (found)
return true; /* This is the second device. */
found = true; /* Found the first device. */
}
return false;
}
static int find_pci_or_platform_parent(sd_device *device, sd_device **ret) {
sd_device *parent;
const char *s;
int r;
assert(device);
assert(ret);
r = sd_device_get_parent(device, &parent);
if (r < 0)
return r;
if (device_in_subsystem(parent, "drm")) {
r = sd_device_get_sysname(parent, &s);
if (r < 0)
return r;
s = startswith(s, "card");
if (!s)
return -ENODATA;
s += strspn(s, DIGITS);
if (*s == '-' && !STARTSWITH_SET(s, "-LVDS-", "-Embedded DisplayPort-", "-eDP-"))
/* A connector DRM device, let's ignore all but LVDS and eDP! */
return -EOPNOTSUPP;
} else if (device_in_subsystem(parent, "pci") &&
sd_device_get_sysattr_value(parent, "class", &s)) {
unsigned long class;
r = safe_atolu(s, &class);
if (r < 0)
return log_device_warning_errno(parent, r, "Cannot parse PCI class '%s': %m", s);
/* Graphics card */
if (class == PCI_CLASS_GRAPHICS_CARD) {
*ret = parent;
return 0;
}
} else if (device_in_subsystem(parent, "platform")) {
*ret = parent;
return 0;
}
return find_pci_or_platform_parent(parent, ret);
}
static int same_device(sd_device *a, sd_device *b) {
const char *a_val, *b_val;
int r;
assert(a);
assert(b);
r = sd_device_get_subsystem(a, &a_val);
if (r < 0)
return r;
r = sd_device_get_subsystem(b, &b_val);
if (r < 0)
return r;
if (!streq(a_val, b_val))
return false;
r = sd_device_get_sysname(a, &a_val);
if (r < 0)
return r;
r = sd_device_get_sysname(b, &b_val);
if (r < 0)
return r;
return streq(a_val, b_val);
}
static int validate_device(sd_device *device) {
_cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *enumerate = NULL;
const char *v, *sysname;
sd_device *parent;
int r;
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. */
r = sd_device_get_sysname(device, &sysname);
if (r < 0)
return log_device_debug_errno(device, r, "Failed to get sysname: %m");
if (!device_in_subsystem(device, "backlight"))
return true; /* We assume LED device is always valid. */
r = sd_device_get_sysattr_value(device, "type", &v);
if (r < 0)
return log_device_debug_errno(device, r, "Failed to read 'type' sysattr: %m");
if (!streq(v, "raw"))
return true;
r = find_pci_or_platform_parent(device, &parent);
if (r < 0)
return log_device_debug_errno(device, r, "Failed to find PCI or platform parent: %m");
if (DEBUG_LOGGING) {
const char *s = NULL, *subsystem = NULL;
(void) sd_device_get_syspath(parent, &s);
(void) sd_device_get_subsystem(parent, &subsystem);
log_device_debug(device, "Found %s parent device: %s", strna(subsystem), strna(s));
}
r = sd_device_enumerator_new(&enumerate);
if (r < 0)
return log_oom_debug();
r = sd_device_enumerator_allow_uninitialized(enumerate);
if (r < 0)
return log_debug_errno(r, "Failed to allow uninitialized devices: %m");
r = sd_device_enumerator_add_match_subsystem(enumerate, "backlight", /* match = */ true);
if (r < 0)
return log_debug_errno(r, "Failed to add subsystem match: %m");
r = sd_device_enumerator_add_nomatch_sysname(enumerate, sysname);
if (r < 0)
return log_debug_errno(r, "Failed to add sysname unmatch: %m");
r = sd_device_enumerator_add_match_sysattr(enumerate, "type", "platform", /* match = */ true);
if (r < 0)
return log_debug_errno(r, "Failed to add sysattr match: %m");
r = sd_device_enumerator_add_match_sysattr(enumerate, "type", "firmware", /* match = */ true);
if (r < 0)
return log_debug_errno(r, "Failed to add sysattr match: %m");
if (device_in_subsystem(parent, "pci")) {
r = has_multiple_graphics_cards();
if (r < 0)
return log_debug_errno(r, "Failed to check if the system has multiple graphics cards: %m");
if (r > 0) {
/* If the system has multiple graphics cards, then we cannot associate platform
* devices on non-PCI bus (especially WMI bus) with PCI devices. Let's ignore all
* backlight devices that do not have the same parent PCI device. */
log_debug("Found multiple graphics cards on PCI bus; "
"skipping deduplication of platform backlight devices not on PCI bus.");
r = sd_device_enumerator_add_match_parent(enumerate, parent);
if (r < 0)
return log_debug_errno(r, "Failed to add parent match: %m");
}
}
FOREACH_DEVICE(enumerate, other) {
sd_device *other_parent;
/* OK, so there's another backlight device, and it's a platform or firmware device.
* Let's see if we can verify it belongs to the same device as ours. */
r = find_pci_or_platform_parent(other, &other_parent);
if (r < 0) {
log_device_debug_errno(other, r, "Failed to get PCI or platform parent, ignoring: %m");
continue;
}
if (same_device(parent, other_parent) > 0) {
/* Both have the same PCI parent, that means we are out. */
if (DEBUG_LOGGING) {
const char *other_sysname = NULL, *other_type = NULL;
(void) sd_device_get_sysname(other, &other_sysname);
(void) sd_device_get_sysattr_value(other, "type", &other_type);
log_device_debug(device,
"Found another %s backlight device %s on the same PCI, skipping.",
strna(other_type), strna(other_sysname));
}
return false;
}
if (device_in_subsystem(other_parent, "platform") && device_in_subsystem(parent, "pci")) {
/* The other is connected to the platform bus and we are a PCI device, that also means we are out. */
if (DEBUG_LOGGING) {
const char *other_sysname = NULL, *other_type = NULL;
(void) sd_device_get_sysname(other, &other_sysname);
(void) sd_device_get_sysattr_value(other, "type", &other_type);
log_device_debug(device,
"Found another %s backlight device %s, which has higher precedence, skipping.",
strna(other_type), strna(other_sysname));
}
return false;
}
}
return true;
}
static int read_max_brightness(sd_device *device, unsigned *ret) {
unsigned max_brightness;
const char *s;
int r;
assert(device);
assert(ret);
r = sd_device_get_sysattr_value(device, "max_brightness", &s);
if (r < 0)
return log_device_warning_errno(device, r, "Failed to read 'max_brightness' attribute: %m");
r = safe_atou(s, &max_brightness);
if (r < 0)
return log_device_warning_errno(device, r, "Failed to parse 'max_brightness' \"%s\": %m", s);
/* 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. */
if (max_brightness == 0) {
log_device_warning(device, "Maximum brightness is 0, ignoring device.");
*ret = 0;
return 0;
}
log_device_debug(device, "Maximum brightness is %u", max_brightness);
*ret = max_brightness;
return 1; /* valid max brightness */
}
static int clamp_brightness(
sd_device *device,
unsigned percent,
bool saved,
unsigned max_brightness,
unsigned *brightness) {
unsigned new_brightness, min_brightness;
assert(device);
assert(brightness);
/* Some systems turn the backlight all the way off at the lowest levels. This 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. */
min_brightness = (unsigned) ((double) max_brightness * percent / 100);
if (device_in_subsystem(device, "backlight"))
min_brightness = MAX(1U, min_brightness);
new_brightness = CLAMP(*brightness, min_brightness, max_brightness);
if (new_brightness != *brightness)
log_device_info(device, "%s brightness %u is %s to %u.",
saved ? "Saved" : "Current",
*brightness,
new_brightness > *brightness ?
"too low; increasing" : "too high; decreasing",
new_brightness);
*brightness = new_brightness;
return 0;
}
static bool shall_clamp(sd_device *device, unsigned *ret) {
const char *property, *s;
unsigned default_percent;
int r;
assert(device);
assert(ret);
if (device_in_subsystem(device, "backlight")) {
property = "ID_BACKLIGHT_CLAMP";
default_percent = 5;
} else {
property = "ID_LEDS_CLAMP";
default_percent = 0;
}
r = sd_device_get_property_value(device, property, &s);
if (r < 0) {
if (r != -ENOENT)
log_device_debug_errno(device, r, "Failed to get %s property, ignoring: %m", property);
*ret = default_percent;
return default_percent > 0;
}
r = parse_boolean(s);
if (r >= 0) {
*ret = r ? 5 : 0;
return r;
}
r = parse_percent(s);
if (r < 0) {
log_device_debug_errno(device, r, "Failed to parse %s property, ignoring: %m", property);
*ret = default_percent;
return default_percent > 0;
}
*ret = r;
return true;
}
static int read_brightness(sd_device *device, unsigned max_brightness, unsigned *ret_brightness) {
const char *value;
unsigned brightness;
int r;
assert(device);
assert(ret_brightness);
if (device_in_subsystem(device, "backlight")) {
r = sd_device_get_sysattr_value(device, "actual_brightness", &value);
if (r == -ENOENT) {
log_device_debug_errno(device, r, "Failed to read 'actual_brightness' attribute, "
"fall back to use 'brightness' attribute: %m");
goto use_brightness;
}
if (r < 0)
return log_device_debug_errno(device, r, "Failed to read 'actual_brightness' attribute: %m");
r = safe_atou(value, &brightness);
if (r < 0) {
log_device_debug_errno(device, r, "Failed to parse 'actual_brightness' attribute, "
"fall back to use 'brightness' attribute: %s", value);
goto use_brightness;
}
if (brightness > max_brightness) {
log_device_debug(device, "actual_brightness=%u is larger than max_brightness=%u, "
"fall back to use 'brightness' attribute", brightness, max_brightness);
goto use_brightness;
}
log_device_debug(device, "Current actual_brightness is %u", brightness);
*ret_brightness = brightness;
return 0;
}
use_brightness:
r = sd_device_get_sysattr_value(device, "brightness", &value);
if (r < 0)
return log_device_debug_errno(device, r, "Failed to read 'brightness' attribute: %m");
r = safe_atou(value, &brightness);
if (r < 0)
return log_device_debug_errno(device, r, "Failed to parse 'brightness' attribute: %s", value);
if (brightness > max_brightness)
return log_device_debug_errno(device, SYNTHETIC_ERRNO(EINVAL),
"brightness=%u is larger than max_brightness=%u",
brightness, max_brightness);
log_device_debug(device, "Current brightness is %u", brightness);
*ret_brightness = brightness;
return 0;
}
static int build_save_file_path(sd_device *device, char **ret) {
_cleanup_free_ char *escaped_subsystem = NULL, *escaped_sysname = NULL, *path = NULL;
const char *s;
int r;
assert(device);
assert(ret);
r = sd_device_get_subsystem(device, &s);
if (r < 0)
return log_device_error_errno(device, r, "Failed to get subsystem: %m");
escaped_subsystem = cescape(s);
if (!escaped_subsystem)
return log_oom();
r = sd_device_get_sysname(device, &s);
if (r < 0)
return log_device_error_errno(device, r, "Failed to get sysname: %m");
escaped_sysname = cescape(s);
if (!escaped_sysname)
return log_oom();
if (sd_device_get_property_value(device, "ID_PATH", &s) >= 0) {
_cleanup_free_ char *escaped_path_id = cescape(s);
if (!escaped_path_id)
return log_oom();
path = strjoin("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_subsystem, ":", escaped_sysname);
} else
path = strjoin("/var/lib/systemd/backlight/", escaped_subsystem, ":", escaped_sysname);
if (!path)
return log_oom();
*ret = TAKE_PTR(path);
return 0;
}
static int read_saved_brightness(sd_device *device, unsigned *ret) {
_cleanup_free_ char *path = NULL, *value = NULL;
int r;
assert(device);
assert(ret);
r = build_save_file_path(device, &path);
if (r < 0)
return r;
r = read_one_line_file(path, &value);
if (r < 0) {
if (r != -ENOENT)
log_device_error_errno(device, r, "Failed to read %s: %m", path);
return r;
}
r = safe_atou(value, ret);
if (r < 0) {
log_device_warning_errno(device, r,
"Failed to parse saved brightness '%s', removing %s.",
value, path);
(void) unlink(path);
return r;
}
log_device_debug(device, "Using saved brightness %u.", *ret);
return 0;
}
static int device_new_from_arg(const char *s, sd_device **ret) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
_cleanup_free_ char *subsystem = NULL;
const char *sysname;
int r;
assert(s);
assert(ret);
sysname = strchr(s, ':');
if (!sysname)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Requires a subsystem and sysname pair specifying a backlight or LED device.");
subsystem = strndup(s, sysname - s);
if (!subsystem)
return log_oom();
sysname++;
if (!STR_IN_SET(subsystem, "backlight", "leds"))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Not a backlight or LED device: '%s:%s'",
subsystem, sysname);
r = sd_device_new_from_subsystem_sysname(&device, subsystem, sysname);
if (r == -ENODEV) {
/* Some drivers, e.g. for AMD GPU, removes acpi backlight device soon after it is added.
* See issue #21997. */
log_debug_errno(r, "Failed to get backlight or LED device '%s:%s', ignoring: %m", subsystem, sysname);
*ret = NULL;
return 0;
}
if (r < 0)
return log_error_errno(r, "Failed to get backlight or LED device '%s:%s': %m", subsystem, sysname);
*ret = TAKE_PTR(device);
return 1; /* Found. */
}
static int verb_load(int argc, char *argv[], void *userdata) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
unsigned max_brightness, brightness, percent;
bool clamp;
int r;
assert(argc == 2);
if (!shall_restore_state())
return 0;
r = device_new_from_arg(argv[1], &device);
if (r <= 0)
return r;
r = read_max_brightness(device, &max_brightness);
if (r <= 0)
return r;
/* Ignore any errors in validation, and use the device as is. */
if (validate_device(device) == 0)
return 0;
clamp = shall_clamp(device, &percent);
r = read_saved_brightness(device, &brightness);
if (r < 0) {
/* Fallback to clamping current brightness or exit early if clamping is not
* supported/enabled. */
if (!clamp)
return 0;
r = read_brightness(device, max_brightness, &brightness);
if (r < 0)
return log_device_error_errno(device, r, "Failed to read current brightness: %m");
(void) clamp_brightness(device, percent, /* saved = */ false, max_brightness, &brightness);
} else if (clamp)
(void) clamp_brightness(device, percent, /* saved = */ true, max_brightness, &brightness);
r = sd_device_set_sysattr_valuef(device, "brightness", "%u", brightness);
if (r < 0)
return log_device_error_errno(device, r, "Failed to write system 'brightness' attribute: %m");
return 0;
}
static int verb_save(int argc, char *argv[], void *userdata) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
_cleanup_free_ char *path = NULL;
unsigned max_brightness, brightness;
int r;
assert(argc == 2);
r = device_new_from_arg(argv[1], &device);
if (r <= 0)
return r;
r = read_max_brightness(device, &max_brightness);
if (r <= 0)
return r;
r = build_save_file_path(device, &path);
if (r < 0)
return r;
/* 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 (validate_device(device) == 0) {
(void) unlink(path);
return 0;
}
r = read_brightness(device, max_brightness, &brightness);
if (r < 0)
return log_device_error_errno(device, r, "Failed to read current brightness: %m");
r = write_string_filef(path, WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_MKDIR_0755, "%u", brightness);
if (r < 0)
return log_device_error_errno(device, r, "Failed to write %s: %m", path);
return 0;
}
static int run(int argc, char *argv[]) {
static const Verb verbs[] = {
{ "load", 2, 2, VERB_ONLINE_ONLY, verb_load },
{ "save", 2, 2, VERB_ONLINE_ONLY, verb_save },
{}
};
log_setup();
if (argv_looks_like_help(argc, argv))
return help();
umask(0022);
return dispatch_verb(argc, argv, verbs, NULL);
}
DEFINE_MAIN_FUNCTION(run);
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