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

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Message-ID: <553006b6-4884-17ca-96cd-7ef6d60a38bf@redhat.com>
Date:   Mon, 19 Feb 2018 10:32:15 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        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>,
        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 15:22, Heikki Krogerus wrote:
> On Fri, Feb 16, 2018 at 04:07:59PM +0200, 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?
> 
> No, this is callback for class_find_device(). It takes int so int it
> is.
> 
>>> +{
>>> +       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;
> 
> Sure. Hans, can you clean-up this as well?

Yes I can, not sure when exactly I will get around to this, but I will
try to get out a v2 addressing all comments made this week.

And thank you for your reviews.

Andy, thank you for all the reviews too.

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?
> 
> No. Check usb_role_switch_release().
> 
> 
> Thanks,
>