Re: [PATCH v5] usb: typec: Add a sysfs node to manage port type

[Guenter Roeck]

On 05/27/2017 01:52 PM, Badhri Jagan Sridharan wrote:
> 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>

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

> ---
> 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.
>
> Changelog since v2:
> - introduced a new mutex lock to protect port_type for addressing
>    the race conditions identified by Geunter Roeck
> - added typec_port_types_drp for printing port_type when cap->type
>    is TYPE_PORT_DRP as suggested by Geunter Roeck
> - Power role swap and data role swaps would be rejected unless
>    port port_type == TYPE_PORT_DRP
> - port_type_store would return immediately if the current port_type
>    is same as the new port_type as suggested by Geunter Roeck
>
> Changelog since v3:
> - Moved as much as code outside port_type_lock as suggested by
>    Geunter Roeck
> - Removed Change-Id line from commit message identified by
>    Greg Kroah-Hartman
>
> Changelog since v4:
> - Corrected return value and moved moved one more line of code
>    outside log in the port_type_store function as suggested

not that it matters: s/log/lock/

>    by Geunter Roeck

and s/Geunter/Guenter/ ;-)

>   drivers/usb/typec/typec.c | 106 +++++++++++++++++++++++++++++++++++++++++-----
>   include/linux/usb/typec.h |   4 ++
>   2 files changed, 100 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/usb/typec/typec.c b/drivers/usb/typec/typec.c
> index 89e540bb7ff3..63644785ce31 100644
> --- a/drivers/usb/typec/typec.c
> +++ b/drivers/usb/typec/typec.c
> @@ -11,6 +11,7 @@
>   
>   #include <linux/device.h>
>   #include <linux/module.h>
> +#include <linux/mutex.h>
>   #include <linux/slab.h>
>   #include <linux/usb/typec.h>
>   
> @@ -69,6 +70,8 @@ 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;
> +	struct mutex			port_type_lock;
>   
>   	const struct typec_capability	*cap;
>   };
> @@ -789,6 +792,18 @@ 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 const char * const typec_port_types_drp[] = {
> +	[TYPEC_PORT_DFP] = "dual [source] sink",
> +	[TYPEC_PORT_UFP] = "dual source [sink]",
> +	[TYPEC_PORT_DRP] = "[dual] source sink",
> +};
> +
>   static ssize_t
>   preferred_role_store(struct device *dev, struct device_attribute *attr,
>   		     const char *buf, size_t size)
> @@ -846,11 +861,6 @@ static ssize_t data_role_store(struct device *dev,
>   	struct typec_port *port = to_typec_port(dev);
>   	int ret;
>   
> -	if (port->cap->type != TYPEC_PORT_DRP) {
> -		dev_dbg(dev, "data role swap only supported with DRP ports\n");
> -		return -EOPNOTSUPP;
> -	}
> -
>   	if (!port->cap->dr_set) {
>   		dev_dbg(dev, "data role swapping not supported\n");
>   		return -EOPNOTSUPP;
> @@ -860,11 +870,22 @@ static ssize_t data_role_store(struct device *dev,
>   	if (ret < 0)
>   		return ret;
>   
> +	mutex_lock(&port->port_type_lock);
> +	if (port->port_type != TYPEC_PORT_DRP) {
> +		dev_dbg(dev, "port type fixed at \"%s\"",
> +			     typec_port_types[port->port_type]);
> +		ret = -EOPNOTSUPP;
> +		goto unlock_and_ret;
> +	}
> +
>   	ret = port->cap->dr_set(port->cap, ret);
>   	if (ret)
> -		return ret;
> +		goto unlock_and_ret;
>   
> -	return size;
> +	ret = size;
> +unlock_and_ret:
> +	mutex_unlock(&port->port_type_lock);
> +	return ret;
>   }
>   
>   static ssize_t data_role_show(struct device *dev,
> @@ -885,7 +906,7 @@ static ssize_t power_role_store(struct device *dev,
>   				const char *buf, size_t size)
>   {
>   	struct typec_port *port = to_typec_port(dev);
> -	int ret = size;
> +	int ret;
>   
>   	if (!port->cap->pd_revision) {
>   		dev_dbg(dev, "USB Power Delivery not supported\n");
> @@ -906,11 +927,22 @@ static ssize_t power_role_store(struct device *dev,
>   	if (ret < 0)
>   		return ret;
>   
> +	mutex_lock(&port->port_type_lock);
> +	if (port->port_type != TYPEC_PORT_DRP) {
> +		dev_dbg(dev, "port type fixed at \"%s\"",
> +			     typec_port_types[port->port_type]);
> +		ret = -EOPNOTSUPP;
> +		goto unlock_and_ret;
> +	}
> +
>   	ret = port->cap->pr_set(port->cap, ret);
>   	if (ret)
> -		return ret;
> +		goto unlock_and_ret;
>   
> -	return size;
> +	ret = size;
> +unlock_and_ret:
> +	mutex_unlock(&port->port_type_lock);
> +	return ret;
>   }
>   
>   static ssize_t power_role_show(struct device *dev,
> @@ -926,6 +958,57 @@ 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;
> +	enum typec_port_type 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;
> +	mutex_lock(&port->port_type_lock);
> +
> +	if (port->port_type == type) {
> +		ret = size;
> +		goto unlock_and_ret;
> +	}
> +
> +	ret = port->cap->port_type_set(port->cap, type);
> +	if (ret)
> +		goto unlock_and_ret;
> +
> +	port->port_type = type;
> +	ret = size;
> +
> +unlock_and_ret:
> +	mutex_unlock(&port->port_type_lock);
> +	return ret;
> +}
> +
> +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)
> +		return sprintf(buf, "%s\n",
> +			       typec_port_types_drp[port->port_type]);
> +
> +	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 +1118,7 @@ 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);
> @@ -1211,6 +1295,8 @@ struct typec_port *typec_register_port(struct device *parent,
>   
>   	port->id = id;
>   	port->cap = cap;
> +	port->port_type = cap->type;
> +	mutex_init(&port->port_type_lock);
>   	port->prefer_role = cap->prefer_role;
>   
>   	port->dev.class = typec_class;
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index ec78204964ab..b174248af7c9 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. */