greybus: interface: add interface-type attribute

Add an interface-type string attribute that represents the detected
interface type as either "dummy", "unipro", "greybus", or "unknown".
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Sandeep Patil <sspatil@google.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/Documentation/sysfs-bus-greybus

@@ -82,6 +82,14 @@ Contact:	Greg Kroah-Hartman <greg@kroah.com>
 Description:
 		The ID of a Greybus interface.
 
+What:		/sys/bus/greybus/devices/N-M.I/interface_type
+Date:		June 2016
+KernelVersion:	4.XX
+Contact:	Greg Kroah-Hartman <greg@kroah.com>
+Description:
+		The type of a Greybus interface; "dummy", "unipro", "greybus",
+		or "unknown".
+
 What:		/sys/bus/greybus/devices/N-M.I/power_now
 Date:		March 2016
 KernelVersion:	4.XX

drivers/staging/greybus/interface.c

@@ -491,6 +491,27 @@ static ssize_t power_now_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(power_now);
 
+static const char *gb_interface_type_string(struct gb_interface *intf)
+{
+	static const char * const types[] = {
+		[GB_SVC_INTF_TYPE_UNKNOWN] = "unknown",
+		[GB_SVC_INTF_TYPE_DUMMY] = "dummy",
+		[GB_SVC_INTF_TYPE_UNIPRO] = "unipro",
+		[GB_SVC_INTF_TYPE_GREYBUS] = "greybus",
+	};
+
+	return types[intf->type];
+}
+
+static ssize_t interface_type_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct gb_interface *intf = to_gb_interface(dev);
+
+	return sprintf(buf, "%s\n", gb_interface_type_string(intf));
+}
+static DEVICE_ATTR_RO(interface_type);
+
 static struct attribute *interface_attrs[] = {
 	&dev_attr_ddbl1_manufacturer_id.attr,
 	&dev_attr_ddbl1_product_id.attr,
@@ -501,6 +522,7 @@ static struct attribute *interface_attrs[] = {
 	&dev_attr_voltage_now.attr,
 	&dev_attr_current_now.attr,
 	&dev_attr_power_now.attr,
+	&dev_attr_interface_type.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(interface);
@@ -721,6 +743,8 @@ static int gb_interface_activate_operation(struct gb_interface *intf)
 		return ret;
 	}
 
+	intf->type = type;
+
 	switch (type) {
 	case GB_SVC_INTF_TYPE_DUMMY:
 		dev_info(&intf->dev, "dummy interface detected\n");
@@ -734,6 +758,7 @@ static int gb_interface_activate_operation(struct gb_interface *intf)
 		break;
 	default:
 		dev_err(&intf->dev, "unknown interface type: %u\n", type);
+		intf->type = GB_SVC_INTF_TYPE_UNKNOWN;
 		return -ENODEV;
 	}
 

drivers/staging/greybus/interface.h

@@ -26,6 +26,7 @@ struct gb_interface {
 	u8 interface_id;	/* Physical location within the Endo */
 	u8 device_id;
 	u8 features;		/* Feature flags set in the manifest */
+	u8 type;
 
 	u32 ddbl1_manufacturer_id;
 	u32 ddbl1_product_id;