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-rw-r--r--src/backlight/backlight.c431
1 files changed, 431 insertions, 0 deletions
diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
new file mode 100644
index 0000000..780ad56
--- /dev/null
+++ b/src/backlight/backlight.c
@@ -0,0 +1,431 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#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 "proc-cmdline.h"
+#include "string-util.h"
+#include "strv.h"
+#include "util.h"
+
+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 == '-') {
+ /* A connector DRM device, let's ignore all but LVDS and eDP! */
+ if (!STARTSWITH_SET(c, "-LVDS-", "-Embedded DisplayPort-"))
+ return -EOPNOTSUPP;
+ }
+
+ } else if (streq(subsystem, "pci") &&
+ sd_device_get_sysattr_value(parent, "class", &value) >= 0) {
+ unsigned long class = 0;
+
+ 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 == 0x30000) {
+ *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, *subsystem;
+ sd_device *parent, *other;
+ 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_subsystem(device, &subsystem);
+ if (r < 0)
+ return r;
+ if (!streq(subsystem, "backlight"))
+ return true;
+
+ r = sd_device_get_sysattr_value(device, "type", &v);
+ if (r < 0)
+ return r;
+ if (!streq(v, "raw"))
+ return true;
+
+ r = find_pci_or_platform_parent(device, &parent);
+ if (r < 0)
+ return r;
+
+ r = sd_device_get_subsystem(parent, &subsystem);
+ if (r < 0)
+ return r;
+
+ r = sd_device_enumerator_new(&enumerate);
+ if (r < 0)
+ return r;
+
+ r = sd_device_enumerator_allow_uninitialized(enumerate);
+ if (r < 0)
+ return r;
+
+ r = sd_device_enumerator_add_match_subsystem(enumerate, "backlight", true);
+ if (r < 0)
+ return r;
+
+ FOREACH_DEVICE(enumerate, other) {
+ const char *other_subsystem;
+ sd_device *other_parent;
+
+ if (same_device(device, other) > 0)
+ continue;
+
+ if (sd_device_get_sysattr_value(other, "type", &v) < 0 ||
+ !STR_IN_SET(v, "platform", "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. */
+ if (find_pci_or_platform_parent(other, &other_parent) < 0)
+ continue;
+
+ if (same_device(parent, other_parent)) {
+ const char *device_sysname = NULL, *other_sysname = NULL;
+
+ /* Both have the same PCI parent, that means we are out. */
+
+ (void) sd_device_get_sysname(device, &device_sysname);
+ (void) sd_device_get_sysname(other, &other_sysname);
+
+ log_debug("Skipping backlight device %s, since device %s is on same PCI device and takes precedence.",
+ device_sysname, other_sysname);
+ return false;
+ }
+
+ if (sd_device_get_subsystem(other_parent, &other_subsystem) < 0)
+ continue;
+
+ if (streq(other_subsystem, "platform") && streq(subsystem, "pci")) {
+ const char *device_sysname = NULL, *other_sysname = NULL;
+
+ /* The other is connected to the platform bus and we are a PCI device, that also means we are out. */
+
+ (void) sd_device_get_sysname(device, &device_sysname);
+ (void) sd_device_get_sysname(other, &other_sysname);
+
+ log_debug("Skipping backlight device %s, since device %s is a platform device and takes precedence.",
+ device_sysname, other_sysname);
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static int get_max_brightness(sd_device *device, unsigned *ret) {
+ const char *max_brightness_str;
+ unsigned max_brightness;
+ int r;
+
+ assert(device);
+ assert(ret);
+
+ r = sd_device_get_sysattr_value(device, "max_brightness", &max_brightness_str);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to read 'max_brightness' attribute: %m");
+
+ r = safe_atou(max_brightness_str, &max_brightness);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to parse 'max_brightness' \"%s\": %m", max_brightness_str);
+
+ if (max_brightness <= 0) {
+ log_device_warning(device, "Maximum brightness is 0, ignoring device.");
+ return -EINVAL;
+ }
+
+ *ret = max_brightness;
+ return 0;
+}
+
+/* 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 int clamp_brightness(sd_device *device, char **value, unsigned max_brightness) {
+ unsigned brightness, new_brightness, min_brightness;
+ const char *subsystem;
+ int r;
+
+ assert(value);
+ assert(*value);
+
+ r = safe_atou(*value, &brightness);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to parse brightness \"%s\": %m", *value);
+
+ 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, max_brightness/20);
+ else
+ min_brightness = 0;
+
+ new_brightness = CLAMP(brightness, min_brightness, max_brightness);
+ if (new_brightness != brightness) {
+ char *new_value;
+
+ r = asprintf(&new_value, "%u", new_brightness);
+ if (r < 0)
+ return log_oom();
+
+ log_device_info(device, "Saved brightness %s %s to %s.", *value,
+ new_brightness > brightness ?
+ "too low; increasing" : "too high; decreasing",
+ new_value);
+
+ free_and_replace(*value, new_value);
+ }
+
+ return 0;
+}
+
+static bool shall_clamp(sd_device *d) {
+ const char *s;
+ int r;
+
+ assert(d);
+
+ r = sd_device_get_property_value(d, "ID_BACKLIGHT_CLAMP", &s);
+ if (r < 0) {
+ log_device_debug_errno(d, r, "Failed to get ID_BACKLIGHT_CLAMP property, ignoring: %m");
+ return true;
+ }
+
+ r = parse_boolean(s);
+ if (r < 0) {
+ log_device_debug_errno(d, r, "Failed to parse ID_BACKLIGHT_CLAMP property, ignoring: %m");
+ return true;
+ }
+
+ return r;
+}
+
+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;
+ int r;
+
+ if (argc != 3) {
+ log_error("This program requires two arguments.");
+ return -EINVAL;
+ }
+
+ log_setup_service();
+
+ 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) {
+ log_error("Requires a subsystem and sysname pair specifying a backlight device.");
+ return -EINVAL;
+ }
+
+ ss = strndupa(argv[2], sysname - argv[2]);
+
+ sysname++;
+
+ if (!STR_IN_SET(ss, "backlight", "leds")) {
+ log_error("Not a backlight or LED device: '%s:%s'", ss, sysname);
+ return -EINVAL;
+ }
+
+ r = sd_device_new_from_subsystem_sysname(&device, ss, sysname);
+ if (r < 0)
+ return log_error_errno(r, "Failed to get backlight or LED device '%s:%s': %m", ss, sysname);
+
+ /* 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;
+
+ 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;
+ bool clamp;
+
+ if (shall_restore_state() == 0)
+ return 0;
+
+ if (validate_device(device) == 0)
+ return 0;
+
+ clamp = shall_clamp(device);
+
+ r = read_one_line_file(saved, &value);
+ if (r == -ENOENT) {
+ const char *curval;
+
+ /* Fallback to clamping current brightness or exit early if
+ * clamping is not supported/enabled. */
+ if (!clamp)
+ return 0;
+
+ r = sd_device_get_sysattr_value(device, "brightness", &curval);
+ if (r < 0)
+ return log_device_warning_errno(device, r, "Failed to read 'brightness' attribute: %m");
+
+ value = strdup(curval);
+ if (!value)
+ return log_oom();
+ } else if (r < 0)
+ return log_error_errno(r, "Failed to read %s: %m", saved);
+
+ if (clamp)
+ (void) clamp_brightness(device, &value, max_brightness);
+
+ r = sd_device_set_sysattr_value(device, "brightness", value);
+ if (r < 0)
+ return log_device_error_errno(device, r, "Failed to write system 'brightness' attribute: %m");
+
+ } else if (streq(argv[1], "save")) {
+ const char *value;
+
+ if (validate_device(device) == 0) {
+ unlink(saved);
+ return 0;
+ }
+
+ r = sd_device_get_sysattr_value(device, "brightness", &value);
+ if (r < 0)
+ return log_device_error_errno(device, r, "Failed to read system 'brightness' attribute: %m");
+
+ r = write_string_file(saved, value, WRITE_STRING_FILE_CREATE);
+ if (r < 0)
+ return log_device_error_errno(device, r, "Failed to write %s: %m", saved);
+
+ } else {
+ log_error("Unknown verb %s.", argv[1]);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);
generated by cgit v1.2.3 (git 2.39.1) at 2024-08-13 12:59:25 +0000