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 <bad...@google.com>
---
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.kroge...@linux.intel.com>
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

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