greybus: svc: add intf_eject attribute

		defined by the Endo layout scheme, documented in

		the ARA Module Developer Kit.

What:		/sys/bus/greybus/device/N-svc/intf_eject

Date:		October 2015

KernelVersion:	4.XX

Contact:	Greg Kroah-Hartman <greg@kroah.com>

Description:

		Write the number of the interface that you wish to

		forcibly eject from the system.

What:		/sys/bus/greybus/device/N-svc/unique_id

Date:		October 2015

KernelVersion:	4.XX

}

static DEVICE_ATTR_RO(ap_intf_id);

// FIXME

// This is a hack, we need to do this "right" and clean the interface up

// properly, not just forcibly yank the thing out of the system and hope for the

// best.  But for now, people want their modules to come out without having to

// throw the thing to the ground or get out a screwdriver.

static ssize_t intf_eject_store(struct device *dev,

				struct device_attribute *attr, const char *buf,

				size_t len)

{

	struct gb_svc *svc = to_gb_svc(dev);

	unsigned short intf_id;

	int ret;

	ret = kstrtou16(buf, 10, &intf_id);

	if (ret < 0)

		return ret;

	dev_warn(dev, "Forcibly trying to eject interface %d\n", intf_id);

	ret = gb_svc_intf_eject(svc, intf_id);

	if (ret < 0)

		return ret;

	return len;

}

static DEVICE_ATTR_WO(intf_eject);

static struct attribute *svc_attrs[] = {

	&dev_attr_endo_id.attr,

	&dev_attr_ap_intf_id.attr,

	&dev_attr_intf_eject.attr,

	NULL,

};

ATTRIBUTE_GROUPS(svc);