linux-kernel - Re: [PATCH v5 1/2] usb: USB Type-C connector class

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Date:	Thu, 18 Aug 2016 13:43:38 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Oliver Neukum <oneukum@...e.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v5 1/2] usb: USB Type-C connector class

On Wed, Aug 17, 2016 at 10:53:11AM -0700, Guenter Roeck wrote:
> On Wed, Aug 17, 2016 at 01:34:40PM +0300, Heikki Krogerus wrote:
> > The purpose of USB Type-C connector class is to provide
> > unified interface for the user space to get the status and
> > basic information about USB Type-C connectors on a system,
> > control over data role swapping, and when the port supports
> > USB Power Delivery, also control over power role swapping
> > and Alternate Modes.
> > 
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > ---
> [ ... ]
> > +
> > +static ssize_t
> > +current_data_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;
> > +
> > +	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;
> > +	}
> > +
> > +	if (!port->connected)
> > +		return size;
> 
> I don't think this check should be here. The connection status can change after
> the connection status was checked. We should leave it up to the driver to
> perform the necessary checks.
> 
> This also applies to the other role change store functions.

OK.

Thanks,

-- 
heikki