+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, "0123456789");
+ 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;
+
+ 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 backlight 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 backlight device %s is a platform device and takes precedence.", udev_device_get_sysname(device), udev_device_get_sysname(other));
+ return false;
+ }
+ }
+
+ return true;
+}
+
~ianmdlvl / elogind.git / commitdiff