linux-kernel - Re: [PATCH 04/12] usb: common: Small class for USB role switches

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Date:   Sun, 25 Feb 2018 13:16:52 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 04/12] usb: common: Small class for USB role switches

Hi,

On 16-02-18 15:07, Andy Shevchenko wrote:
> On Fri, Feb 16, 2018 at 12:47 PM, Hans de Goede <hdegoede@...hat.com> wrote:
> 
>> USB role switch is a device that can be used to choose the
>> data role for USB connector. With dual-role capable USB
>> controllers, the controller itself will be the switch, but
>> on some platforms the USB host and device controllers are
>> separate IPs and there is a mux between them and the
>> connector. On those platforms the mux driver will need to
>> register the switch.
>>
>> With USB Type-C connectors, the host-to-device relationship
>> is negotiated over the Configuration Channel (CC). That
>> means the USB Type-C drivers need to be in control of the
>> role switch. The class provides a simple API for the USB
>> Type-C drivers for the control.
>>
>> For other types of USB connectors (mainly microAB) the class
>> provides user space control via sysfs attribute file that
>> can be used to request role swapping from the switch.
> 
>> +static int __switch_match(struct device *dev, const void *name)
> 
> bool?
> 
>> +{
>> +       return !strcmp((const char *)name, dev_name(dev));
>> +}
> 
> 
>> +static ssize_t role_store(struct device *dev, struct device_attribute *attr,
>> +                         const char *buf, size_t size)
>> +{
>> +       struct usb_role_switch *sw = to_role_switch(dev);
>> +       int ret;
>> +
>> +       ret = sysfs_match_string(usb_roles, buf);
>> +       if (ret < 0) {
>> +               bool res;
>> +
>> +               /* Extra check if the user wants to disable the switch */
>> +               ret = kstrtobool(buf, &res);
>> +               if (ret || res)
>> +                       return -EINVAL;
>> +       }
>> +
> 
>> +       ret = usb_role_switch_set_role(sw, ret);
>> +       if (!ret)
>> +               ret = size;
>> +
>> +       return ret;
> 
> Perhaps
> 
> ret = ...
> if (ret)
>   return ret;
> 
> return size;

Ack, that is better, fixed for v2.

Regards,

Hans


> 
>> +}
> 
>> +struct usb_role_switch *
>> +usb_role_switch_register(struct device *parent,
>> +                        const struct usb_role_switch_desc *desc)
>> +{
>> +       struct usb_role_switch *sw;
>> +       int ret;
>> +
>> +       if (!desc || !desc->set)
>> +               return ERR_PTR(-EINVAL);
>> +
>> +       sw = kzalloc(sizeof(*sw), GFP_KERNEL);
>> +       if (!sw)
>> +               return ERR_PTR(-ENOMEM);
> 
>> +       ret = device_register(&sw->dev);
>> +       if (ret) {
>> +               put_device(&sw->dev);
> 
> Memory leak?
> 
>> +               return ERR_PTR(ret);
>> +       }
>> +
>> +       /* TODO: Symlinks for the host port and the device controller. */
>> +
>> +       return sw;
>> +}
> 
>> +void usb_role_switch_unregister(struct usb_role_switch *sw)
>> +{
>> +       if (sw && !IS_ERR(sw))
> 
> !IS_ERR_OR_NULL() ?
> 
>> +               device_unregister(&sw->dev);
>> +}
>