platform/x86: think-lmi: Add pending_reboot support

The Think-lmi driver was missing pending_reboot support as it wasn't
available from the BIOS. Turns out this is really useful to have from
user space so implementing from a purely SW point of view.

Thanks to Mario Limonciello for guidance on how fwupd would use this.
Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mark Pearson <markpearson@lenovo.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210628222846.8830-1-markpearson@lenovo.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/think-lmi.c

@@ -571,6 +571,11 @@ static ssize_t current_value_store(struct kobject *kobj,
 	else
 		ret = tlmi_save_bios_settings("");
 
+	if (!ret && !tlmi_priv.pending_changes) {
+		tlmi_priv.pending_changes = true;
+		/* let userland know it may need to check reboot pending again */
+		kobject_uevent(&tlmi_priv.class_dev->kobj, KOBJ_CHANGE);
+	}
 out:
 	kfree(auth_str);
 	kfree(set_str);
@@ -647,6 +652,14 @@ static struct kobj_type tlmi_pwd_setting_ktype = {
 	.sysfs_ops	= &tlmi_kobj_sysfs_ops,
 };
 
+static ssize_t pending_reboot_show(struct kobject *kobj, struct kobj_attribute *attr,
+				   char *buf)
+{
+	return sprintf(buf, "%d\n", tlmi_priv.pending_changes);
+}
+
+static struct kobj_attribute pending_reboot = __ATTR_RO(pending_reboot);
+
 /* ---- Initialisation --------------------------------------------------------- */
 static void tlmi_release_attr(void)
 {
@@ -667,6 +680,7 @@ static void tlmi_release_attr(void)
 	sysfs_remove_group(&tlmi_priv.pwd_power->kobj, &auth_attr_group);
 	kobject_put(&tlmi_priv.pwd_power->kobj);
 	kset_unregister(tlmi_priv.authentication_kset);
+	sysfs_remove_file(&tlmi_priv.class_dev->kobj, &pending_reboot.attr);
 }
 
 static int tlmi_sysfs_init(void)
@@ -746,6 +760,11 @@ static int tlmi_sysfs_init(void)
 	if (ret)
 		goto fail_create_attr;
 
+	/* Create global sysfs files */
+	ret = sysfs_create_file(&tlmi_priv.class_dev->kobj, &pending_reboot.attr);
+	if (ret)
+		goto fail_create_attr;
+
 	return ret;
 
 fail_create_attr:

drivers/platform/x86/think-lmi.h

@@ -60,6 +60,7 @@ struct think_lmi {
 	bool can_get_bios_selections;
 	bool can_set_bios_password;
 	bool can_get_password_settings;
+	bool pending_changes;
 
 	struct tlmi_attr_setting *setting[TLMI_SETTINGS_COUNT];
 	struct device *class_dev;