Input: serio - add firmware_id sysfs attribute

serio devices exposed via platform firmware interfaces such as ACPI may
provide additional identifying information of use to userspace.

We don't associate the serio devices with the firmware device (we don't
set it as parent), so there's no way for userspace to make use of this
information.

We cannot change the parent for serio devices instantiated though a
firmware interface as that would break suspend / resume ordering.

Therefore this patch adds a new firmware_id sysfs attribute so that
userspace can get a string from there with any additional identifying
information the firmware interface may provide.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/serio/serio.c

@@ -451,6 +451,13 @@ static ssize_t serio_set_bind_mode(struct device *dev, struct device_attribute *
 	return retval;
 }
 
+static ssize_t firmware_id_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct serio *serio = to_serio_port(dev);
+
+	return sprintf(buf, "%s\n", serio->firmware_id);
+}
+
 static DEVICE_ATTR_RO(type);
 static DEVICE_ATTR_RO(proto);
 static DEVICE_ATTR_RO(id);
@@ -473,12 +480,14 @@ static DEVICE_ATTR_RO(modalias);
 static DEVICE_ATTR_WO(drvctl);
 static DEVICE_ATTR(description, S_IRUGO, serio_show_description, NULL);
 static DEVICE_ATTR(bind_mode, S_IWUSR | S_IRUGO, serio_show_bind_mode, serio_set_bind_mode);
+static DEVICE_ATTR_RO(firmware_id);
 
 static struct attribute *serio_device_attrs[] = {
 	&dev_attr_modalias.attr,
 	&dev_attr_description.attr,
 	&dev_attr_drvctl.attr,
 	&dev_attr_bind_mode.attr,
+	&dev_attr_firmware_id.attr,
 	NULL
 };
 
@@ -921,9 +930,14 @@ static int serio_uevent(struct device *dev, struct kobj_uevent_env *env)
 	SERIO_ADD_UEVENT_VAR("SERIO_PROTO=%02x", serio->id.proto);
 	SERIO_ADD_UEVENT_VAR("SERIO_ID=%02x", serio->id.id);
 	SERIO_ADD_UEVENT_VAR("SERIO_EXTRA=%02x", serio->id.extra);
+
 	SERIO_ADD_UEVENT_VAR("MODALIAS=serio:ty%02Xpr%02Xid%02Xex%02X",
 				serio->id.type, serio->id.proto, serio->id.id, serio->id.extra);
 
+	if (serio->firmware_id[0])
+		SERIO_ADD_UEVENT_VAR("SERIO_FIRMWARE_ID=%s",
+				     serio->firmware_id);
+
 	return 0;
 }
 #undef SERIO_ADD_UEVENT_VAR

include/linux/serio.h

@@ -23,6 +23,7 @@ struct serio {
 
 	char name[32];
 	char phys[32];
+	char firmware_id[128];
 
 	bool manual_bind;