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-rw-r--r--src/backlight/backlight.c612
-rw-r--r--src/backlight/meson.build9
2 files changed, 621 insertions, 0 deletions
diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
new file mode 100644
index 0000000..5ac9f90
--- /dev/null
+++ b/src/backlight/backlight.c
@@ -0,0 +1,612 @@
+/* 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 "mkdir.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"
+
+#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_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) {
+ const char *subsystem, *sysname, *value;
+ sd_device *parent;
+ int r;
+
+ assert(device);
+ assert(ret);
+
+ r = sd_device_get_parent(device, &parent);
+ if (r < 0)
+ return r;
+
+ r = sd_device_get_subsystem(parent, &subsystem);
+ if (r < 0)
+ return r;
+
+ r = sd_device_get_sysname(parent, &sysname);
+ if (r < 0)
+ return r;
+
+ if (streq(subsystem, "drm")) {
+ const char *c;
+
+ c = startswith(sysname, "card");
+ if (!c)
+ return -ENODATA;
+
+ c += strspn(c, DIGITS);
+ if (*c == '-' && !STARTSWITH_SET(c, "-LVDS-", "-Embedded DisplayPort-", "-eDP-"))
+ /* A connector DRM device, let's ignore all but LVDS and eDP! */
+ return -EOPNOTSUPP;
+
+ } else if (streq(subsystem, "pci") &&
+ sd_device_get_sysattr_value(parent, "class", &value) >= 0) {
+ unsigned long class;
+
+ r = safe_atolu(value, &class);
+ if (r < 0)
+ return log_warning_errno(r, "Cannot parse PCI class '%s' of device %s:%s: %m",
+ value, subsystem, sysname);
+
+ /* Graphics card */
+ if (class == PCI_CLASS_GRAPHICS_CARD) {
+ *ret = parent;
+ return 0;
+ }
+
+ } else if (streq(subsystem, "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, *subsystem;
+ 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");
+
+ r = sd_device_get_subsystem(device, &subsystem);
+ if (r < 0)
+ return log_device_debug_errno(device, r, "Failed to get subsystem: %m");
+ if (!streq(subsystem, "backlight"))
+ return true;
+
+ 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");
+
+ r = sd_device_get_subsystem(parent, &subsystem);
+ if (r < 0)
+ return log_device_debug_errno(parent, r, "Failed to get subsystem: %m");
+
+ if (DEBUG_LOGGING) {
+ const char *s = NULL;
+
+ (void) sd_device_get_syspath(parent, &s);
+ log_device_debug(device, "Found %s parent device: %s", 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 (streq(subsystem, "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 to associate platform backlight devices on non-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) {
+ const char *other_subsystem;
+ 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;
+ }
+
+ r = sd_device_get_subsystem(other_parent, &other_subsystem);
+ if (r < 0) {
+ log_device_debug_errno(other_parent, r, "Failed to get subsystem, ignoring: %m");
+ continue;
+ }
+
+ if (streq(other_subsystem, "platform") && streq(subsystem, "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 get_max_brightness(sd_device *device, unsigned *ret) {
+ 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, ret);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to parse 'max_brightness' \"%s\": %m", s);
+
+ return 0;
+}
+
+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;
+
+ 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. */
+
+ r = sd_device_get_subsystem(device, &subsystem);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to get device subsystem: %m");
+
+ if (streq(subsystem, "backlight"))
+ min_brightness = MAX(1U, (unsigned) ((double) max_brightness * percent / 100));
+ else
+ min_brightness = 0;
+
+ 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 *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;
+ }
+
+ *ret = r;
+ return true;
+}
+
+static int read_brightness(sd_device *device, unsigned max_brightness, unsigned *ret_brightness) {
+ const char *subsystem, *value;
+ unsigned brightness;
+ int r;
+
+ assert(device);
+ assert(ret_brightness);
+
+ r = sd_device_get_subsystem(device, &subsystem);
+ if (r < 0)
+ return log_device_debug_errno(device, r, "Failed to get subsystem: %m");
+
+ if (streq(subsystem, "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 run(int argc, char *argv[]) {
+ _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+ _cleanup_free_ char *escaped_ss = NULL, *escaped_sysname = NULL, *escaped_path_id = NULL;
+ const char *sysname, *path_id, *ss, *saved;
+ unsigned max_brightness, brightness;
+ int r;
+
+ log_setup();
+
+ if (argv_looks_like_help(argc, argv))
+ return help();
+
+ if (argc != 3)
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program requires two arguments.");
+
+ if (!STR_IN_SET(argv[1], "load", "save"))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unknown verb %s.", argv[1]);
+
+ umask(0022);
+
+ r = mkdir_p("/var/lib/systemd/backlight", 0755);
+ if (r < 0)
+ return log_error_errno(r, "Failed to create backlight directory /var/lib/systemd/backlight: %m");
+
+ sysname = strchr(argv[2], ':');
+ if (!sysname)
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Requires a subsystem and sysname pair specifying a backlight device.");
+
+ ss = strndupa_safe(argv[2], sysname - argv[2]);
+
+ sysname++;
+
+ if (!STR_IN_SET(ss, "backlight", "leds"))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Not a backlight or LED device: '%s:%s'", ss, sysname);
+
+ r = sd_device_new_from_subsystem_sysname(&device, ss, sysname);
+ if (r < 0) {
+ bool ignore = r == -ENODEV;
+
+ /* Some drivers, e.g. for AMD GPU, removes acpi backlight device soon after it is added.
+ * See issue #21997. */
+ log_full_errno(ignore ? LOG_DEBUG : LOG_ERR, r,
+ "Failed to get backlight or LED device '%s:%s'%s: %m",
+ ss, sysname, ignore ? ", ignoring" : "");
+ return ignore ? 0 : r;
+ }
+
+ /* 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 (get_max_brightness(device, &max_brightness) < 0)
+ return 0;
+
+ if (max_brightness == 0) {
+ log_device_warning(device, "Maximum brightness is 0, ignoring device.");
+ return 0;
+ }
+
+ log_device_debug(device, "Maximum brightness is %u", max_brightness);
+
+ escaped_ss = cescape(ss);
+ if (!escaped_ss)
+ return log_oom();
+
+ escaped_sysname = cescape(sysname);
+ if (!escaped_sysname)
+ return log_oom();
+
+ if (sd_device_get_property_value(device, "ID_PATH", &path_id) >= 0) {
+ escaped_path_id = cescape(path_id);
+ if (!escaped_path_id)
+ return log_oom();
+
+ saved = strjoina("/var/lib/systemd/backlight/", escaped_path_id, ":", escaped_ss, ":", escaped_sysname);
+ } else
+ saved = strjoina("/var/lib/systemd/backlight/", escaped_ss, ":", escaped_sysname);
+
+ /* 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;
+ unsigned percent;
+ bool clamp;
+
+ if (!shall_restore_state())
+ return 0;
+
+ if (validate_device(device) == 0)
+ return 0;
+
+ clamp = shall_clamp(device, &percent);
+
+ r = read_one_line_file(saved, &value);
+ if (r < 0 && r != -ENOENT)
+ return log_error_errno(r, "Failed to read %s: %m", saved);
+ if (r > 0) {
+ r = safe_atou(value, &brightness);
+ if (r < 0) {
+ log_warning_errno(r, "Failed to parse saved brightness '%s', removing %s.",
+ value, saved);
+ (void) unlink(saved);
+ } else {
+ log_debug("Using saved brightness %u.", brightness);
+ if (clamp)
+ (void) clamp_brightness(device, percent, /* saved = */ true, max_brightness, &brightness);
+
+ /* Do not fall back to read current brightness below. */
+ r = 1;
+ }
+ }
+ 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);
+ }
+
+ 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");
+
+ } else if (streq(argv[1], "save")) {
+ if (validate_device(device) == 0) {
+ (void) unlink(saved);
+ 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(saved, WRITE_STRING_FILE_CREATE, "%u", brightness);
+ if (r < 0)
+ return log_device_error_errno(device, r, "Failed to write %s: %m", saved);
+
+ } else
+ assert_not_reached();
+
+ return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);
diff --git a/src/backlight/meson.build b/src/backlight/meson.build
new file mode 100644
index 0000000..ed4c55e
--- /dev/null
+++ b/src/backlight/meson.build
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+executables += [
+ libexec_template + {
+ 'name' : 'systemd-backlight',
+ 'conditions' : ['ENABLE_BACKLIGHT'],
+ 'sources' : files('backlight.c'),
+ },
+]