[PATCH v2] usb: typec: Add a sysfs node to manage port type

[Badhri Jagan Sridharan]

User space applications in some cases have the need to enforce a
specific port type(DFP/UFP/DRP). This change allows userspace to
attempt setting the desired port type. Low level drivers can
however reject the request if the specific port type is not supported.

Signed-off-by: Badhri Jagan Sridharan <Badhri@xxxxxxxxxx>
---
Changelog since v1:
- introduced a new variable port_type in struct typec_port to track
  the current port type instead of changing type member in
  typec_capability to address Heikki Krogerus comments.
- changed the output format and strings that would be displayed as
  suggested by Heikki Krogerus.

 Documentation/ABI/testing/sysfs-class-typec | 13 ++++++
 drivers/usb/typec/typec.c                   | 66 +++++++++++++++++++++++++++++
 include/linux/usb/typec.h                   |  4 ++
 3 files changed, 83 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
index d4a3d23eb09c..1f224c2e391f 100644
--- a/Documentation/ABI/testing/sysfs-class-typec
+++ b/Documentation/ABI/testing/sysfs-class-typec
@@ -73,6 +73,19 @@ Description:
 
 		Valid values: source, sink, none (to remove preference)
 
+What:           /sys/class/typec/<port>/port_type
+Date:           May 2017
+Description:
+		Indicates the type of the port. This attribute can be used for
+		requesting a change in the port type. Port type change is
+		supported as a synchronous operation, so write(2) to the
+		attribute will not return until the operation has finished.
+
+		Valid values:
+		- source
+		- sink
+		- dual
+
 What:		/sys/class/typec/<port>/supported_accessory_modes
 Date:		April 2017
 Contact:	Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
diff --git a/drivers/usb/typec/typec.c b/drivers/usb/typec/typec.c
index 89e540bb7ff3..5063d6e0f8c7 100644
--- a/drivers/usb/typec/typec.c
+++ b/drivers/usb/typec/typec.c
@@ -69,6 +69,7 @@ struct typec_port {
 	enum typec_role			pwr_role;
 	enum typec_role			vconn_role;
 	enum typec_pwr_opmode		pwr_opmode;
+	enum typec_port_type		port_type;
 
 	const struct typec_capability	*cap;
 };
@@ -789,6 +790,12 @@ static const char * const typec_data_roles[] = {
 	[TYPEC_HOST]	= "host",
 };
 
+static const char * const typec_port_types[] = {
+	[TYPEC_PORT_DFP] = "source",
+	[TYPEC_PORT_UFP] = "sink",
+	[TYPEC_PORT_DRP] = "dual",
+};
+
 static ssize_t
 preferred_role_store(struct device *dev, struct device_attribute *attr,
 		     const char *buf, size_t size)
@@ -856,6 +863,12 @@ static ssize_t data_role_store(struct device *dev,
 		return -EOPNOTSUPP;
 	}
 
+	if (port->port_type != TYPEC_PORT_DRP) {
+		dev_dbg(dev, "port type fixed at \"%s\"",
+			     typec_port_types[port->port_type]);
+		return -EIO;
+	}
+
 	ret = sysfs_match_string(typec_data_roles, buf);
 	if (ret < 0)
 		return ret;
@@ -897,6 +910,12 @@ static ssize_t power_role_store(struct device *dev,
 		return -EOPNOTSUPP;
 	}
 
+	if (port->port_type != TYPEC_PORT_DRP) {
+		dev_dbg(dev, "port type fixed at \"%s\"",
+			     typec_port_types[port->port_type]);
+		return -EIO;
+	}
+
 	if (port->pwr_opmode != TYPEC_PWR_MODE_PD) {
 		dev_dbg(dev, "partner unable to swap power role\n");
 		return -EIO;
@@ -926,6 +945,52 @@ static ssize_t power_role_show(struct device *dev,
 }
 static DEVICE_ATTR_RW(power_role);
 
+static ssize_t
+port_type_store(struct device *dev, struct device_attribute *attr,
+			const char *buf, size_t size)
+{
+	struct typec_port *port = to_typec_port(dev);
+	int ret, type;
+
+	if (!port->cap->port_type_set || port->cap->type != TYPEC_PORT_DRP) {
+		dev_dbg(dev, "changing port type not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	ret = sysfs_match_string(typec_port_types, buf);
+	if (ret < 0)
+		return ret;
+
+	type = ret;
+
+	ret = port->cap->port_type_set(port->cap, type);
+	if (ret)
+		return ret;
+
+	port->port_type = type;
+
+	return size;
+}
+
+static ssize_t
+port_type_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct typec_port *port = to_typec_port(dev);
+
+	if (port->cap->type == TYPEC_PORT_DRP) {
+		if (port->port_type == TYPEC_PORT_DRP)
+			return sprintf(buf, "%s\n", "[dual] source sink");
+		else if (port->port_type == TYPEC_PORT_DFP)
+			return sprintf(buf, "%s\n", "dual [source] sink");
+		else
+			return sprintf(buf, "%s\n", "dual source [sink]");
+	}
+
+	return sprintf(buf, "[%s]\n", typec_port_types[port->cap->type]);
+}
+static DEVICE_ATTR_RW(port_type);
+
 static const char * const typec_pwr_opmodes[] = {
 	[TYPEC_PWR_MODE_USB]	= "default",
 	[TYPEC_PWR_MODE_1_5A]	= "1.5A",
@@ -1035,6 +1100,7 @@ static struct attribute *typec_attrs[] = {
 	&dev_attr_usb_power_delivery_revision.attr,
 	&dev_attr_usb_typec_revision.attr,
 	&dev_attr_vconn_source.attr,
+	&dev_attr_port_type.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(typec);
diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
index ec78204964ab..5badf6f66479 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -190,6 +190,7 @@ struct typec_partner_desc {
  * @pr_set: Set Power Role
  * @vconn_set: Set VCONN Role
  * @activate_mode: Enter/exit given Alternate Mode
+ * @port_type_set: Set port type
  *
  * Static capabilities of a single USB Type-C port.
  */
@@ -214,6 +215,9 @@ struct typec_capability {
 
 	int		(*activate_mode)(const struct typec_capability *,
 					 int mode, int activate);
+
+	int		(*port_type_set)(const struct typec_capability *,
+					enum typec_port_type);
 };
 
 /* Specific to try_role(). Indicates the user want's to clear the preference. */
-- 
2.13.0.219.gdb65acc882-goog