linux-kernel - Re: [RFC PATCHv2] usb: USB Type-C Connector Class

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Date:	Tue, 24 May 2016 12:28:26 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Oliver Neukum <oneukum@...e.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCHv2] usb: USB Type-C Connector Class

On Thu, May 19, 2016 at 03:44:54PM +0300, Heikki Krogerus wrote:
> The purpose of this class is to provide unified interface for user
> space to get the status and basic information about USB Type-C
> Connectors in the system, control data role swapping, and when USB PD
> is available, also power role swapping and Alternate Modes.
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

[ ... ]

> +
> +static void typec_remove_partner(struct typec_port *port)
> +{
> +	sysfs_remove_link(&port->dev.kobj, "partner");
> +	typec_unregister_altmodes(port->partner->alt_modes);

This only unregisters alternate modes registered through typec_add_partner(),
but not alternate modes registered separately. Or is the calling code expected
to set port->partner->alt_modes when calling typec_register_altmodes()
directly ?

[ ... ]

> +
> +void typec_unregister_altmodes(struct typec_altmode *alt_modes)
> +{
> +	struct typec_altmode *alt;
> +
This will crash if alt_modes is NULL, which will happen if 
partner->alt_modes is NULL at connection time. Semantically
this is different to typec_register_altmodes(), which does
have a NULL check.

Guenter