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

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Date:   Fri, 16 Feb 2018 16:07:59 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hans de Goede <hdegoede@...hat.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

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;

> +}

> +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);
> +}

-- 
With Best Regards,
Andy Shevchenko