Re: [PATCHv3] usb: typec: Add a sysfs node to manage port type

[Badhri Jagan Sridharan]

On Fri, May 26, 2017 at 11:00 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> On Fri, May 26, 2017 at 10:45:59AM -0700, 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>
>> Change-Id: Ia76877558c47271a34d912a54eea3459655dda3c
>> ---
>> 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
>>
>>  drivers/usb/typec/typec.c | 127 ++++++++++++++++++++++++++++++++++++++++------
>>  include/linux/usb/typec.h |   4 ++
>>  2 files changed, 116 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/usb/typec/typec.c b/drivers/usb/typec/typec.c
>> index 89e540bb7ff3..a0d8887ad560 100644
>> --- a/drivers/usb/typec/typec.c
>> +++ b/drivers/usb/typec/typec.c
>> @@ -11,9 +11,11 @@
>>
>>  #include <linux/device.h>
>>  #include <linux/module.h>
>> +#include <linux/mutex.h>
>>  #include <linux/slab.h>
>>  #include <linux/usb/typec.h>
>>
>> +
>
> Single empty lines only, please.
>
>>  struct typec_mode {
>>       int                             index;
>>       u32                             vdo;
>> @@ -69,6 +71,8 @@ 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 +793,19 @@ 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",
>> +};
>> +
>> +
> Single empty line.
>
>>  static ssize_t
>>  preferred_role_store(struct device *dev, struct device_attribute *attr,
>>                    const char *buf, size_t size)
>> @@ -846,25 +863,34 @@ 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;
>> -     }
>> +     mutex_lock(&port->port_type_lock);
>>
>>       if (!port->cap->dr_set) {
>>               dev_dbg(dev, "data role swapping not supported\n");
>> -             return -EOPNOTSUPP;
>> +             ret = -EOPNOTSUPP;
>> +             goto unlock_and_ret;
>> +     }
>
> I think you can check this outside the lock; capabilities won't change.
>
>> +
>> +     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 = sysfs_match_string(typec_data_roles, buf);
>>       if (ret < 0)
>> -             return ret;
>> +             goto unlock_and_ret;
>
> Move outside the lock ?
>
>>
>>       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,
>> @@ -885,32 +911,47 @@ 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;
>>
>> +     mutex_lock(&port->port_type_lock);
>>       if (!port->cap->pd_revision) {
>>               dev_dbg(dev, "USB Power Delivery not supported\n");
>> -             return -EOPNOTSUPP;
>> +             ret = -EOPNOTSUPP;
>> +             goto unlock_and_ret;
>>       }
>>
>>       if (!port->cap->pr_set) {
>>               dev_dbg(dev, "power role swapping not supported\n");
>> -             return -EOPNOTSUPP;
>> +             ret = -EOPNOTSUPP;
>> +             goto unlock_and_ret;
>> +     }
>> +
> Capabilities can be checked outside the 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;
>>       }
>>
>>       if (port->pwr_opmode != TYPEC_PWR_MODE_PD) {
>>               dev_dbg(dev, "partner unable to swap power role\n");
>> -             return -EIO;
>> +             ret = -EIO;
>> +             goto unlock_and_ret;
>>       }
>>
>>       ret = sysfs_match_string(typec_roles, buf);
>>       if (ret < 0)
>> -             return ret;
>> +             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 +967,59 @@ 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;
>> +
>> +     mutex_lock(&port->port_type_lock);
>> +
>> +     if (!port->cap->port_type_set || port->cap->type != TYPEC_PORT_DRP) {
>> +             dev_dbg(dev, "changing port type not supported\n");
>> +             ret = -EOPNOTSUPP;
>> +             goto unlock_and_ret;
>> +     }
>> +
>> +     ret = sysfs_match_string(typec_port_types, buf);
>> +     if (ret < 0)
>> +             goto unlock_and_ret;
>> +
> I would suggest to check as much as possible outside the lock.

Moving as much as possible outside the lock as suggested.

>
>> +     type = ret;
>> +
>> +     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 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)
>> +             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 +1129,7 @@ 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 +1306,8 @@ 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. */
>> --
>> 2.13.0.219.gdb65acc882-goog
>>