On Fri, Feb 16, 2018 at 12:47 PM, Hans de Goede <hdegoede@xxxxxxxxxx> 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
