thunderbolt: Add 'boot' attribute for devices

In various cases, Thunderbolt device can be connected by ICM on boot
without waiting for approval from user. Most cases are related to
OEM-specific BIOS configurations. This information is interesting for
user-space as if the device isn't in SW ACL, it may create a friction in
the user experience where the device is automatically authorized if it's
connected on boot but requires an explicit user action if connected
after OS is up. User-space can use this information to suggest adding
the device to SW ACL for auto-authorization on later connections.

Signed-off-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 4e2b209..e9e30aa 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -775,6 +775,15 @@ static ssize_t authorized_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(authorized);
 
+static ssize_t boot_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct tb_switch *sw = tb_to_switch(dev);
+
+	return sprintf(buf, "%u\n", sw->boot);
+}
+static DEVICE_ATTR_RO(boot);
+
 static ssize_t device_show(struct device *dev, struct device_attribute *attr,
 			   char *buf)
 {
@@ -951,6 +960,7 @@ static DEVICE_ATTR_RO(unique_id);
 
 static struct attribute *switch_attrs[] = {
 	&dev_attr_authorized.attr,
+	&dev_attr_boot.attr,
 	&dev_attr_device.attr,
 	&dev_attr_device_name.attr,
 	&dev_attr_key.attr,
@@ -979,6 +989,10 @@ static umode_t switch_attr_is_visible(struct kobject *kobj,
 		if (sw->dma_port)
 			return attr->mode;
 		return 0;
+	} else if (attr == &dev_attr_boot.attr) {
+		if (tb_route(sw))
+			return attr->mode;
+		return 0;
 	}
 
 	return sw->safe_mode ? 0 : attr->mode;