Re: Aspeed vhub configuration

[Felipe Balbi <balbi@kernel.org>]

Hi,

Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> On Tue, 2019-07-02 at 14:24 +0200, Greg KH wrote:
>> 
>> > That leaves me with two approaches, that aren't mutually exclusive, but
>> > I'd like to run them past the folks here before I start coding:
>> > 
>> >  - The defaults, currently hard coded, could be replaced with Kconfig
>> > options.
>> > 
>> >  - The device-tree node could contain optional override of those
>> > defaults, allowing a vendor to customize the hub for a given board.
>> > It's not per-se a HW description, but the device-tree is also fairly
>> > commonly used for HW configuration, even if some people disagree with
>> > me on that one (hint: they are wrong :-)
>> > 
>> >  - I could add sysfs properties underneath the vhub device instance to
>> > customize it. This would also allow userspace to control whether the
>> > hub is "connected" to the host or not, which could be useful, some
>> > systems don't want it to always be there. Today there's no choice.
>> > 
>> > Any other option ? If somebody says netlink I will scream :)
>> 
>> DT seems like the logical choice, I'll not object to that.
>
> DT for defaults sounds good yes. I'm still toying with also having
> sysfs properties. There have been people wanting to connect or
> disconnect the hub from the host programatically, a property in the
> device node would be best for that. Being able to override the serial
> number as well. The DT isn't a great place for that.

We already have an interface for disconnecting from the host
programatically by disconnecting data pullup.

static ssize_t soft_connect_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t n)
{
	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);

	if (!udc->driver) {
		dev_err(dev, "soft-connect without a gadget driver\n");
		return -EOPNOTSUPP;
	}

	if (sysfs_streq(buf, "connect")) {
		usb_gadget_udc_start(udc);
		usb_gadget_connect(udc->gadget);
	} else if (sysfs_streq(buf, "disconnect")) {
		usb_gadget_disconnect(udc->gadget);
		usb_gadget_udc_stop(udc);
	} else {
		dev_err(dev, "unsupported command '%s'\n", buf);
		return -EINVAL;
	}

	return n;
}
static DEVICE_ATTR_WO(soft_connect);

part of udc/core.c

-- 
balbi