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Subject: Re: [RFC PATCHv3] usb: USB Type-C Connector Class
From: Oliver Neukum <oneukum@suse.com>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        Greg KH <gregkh@linuxfoundation.org>, Pavel Machek <pavel@ucw.cz>,
        linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Date: Sat, 11 Jun 2016 09:05:46 +0200
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	 <1465569269-63856-1-git-send-email-heikki.krogerus@linux.intel.com>
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On Fri, 2016-06-10 at 17:34 +0300, Heikki Krogerus wrote:
> +static ssize_t
> +preferred_role_store(struct device *dev, struct device_attribute
> *attr,
> +                    const char *buf, size_t size)
> +{
> +       struct typec_port *port = to_typec_port(dev);
> +       enum typec_role role;
> +       int ret;
> +
> +       mutex_lock(&port->lock);
> +
> +       if (port->cap->type != TYPEC_PORT_DRP) {
> +               dev_dbg(dev, "Try.SRC/SNK only supported with DRP
> ports\n");
> +               ret = -EOPNOTSUPP;
> +               goto out;
> +       }

I think Try.SNK with an UFP should fail differently from
Try.SRC and vice versa.

And, even more importantly, this offeres no way to cancel
a preference.

	Regards
		Oliver