From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH] HID: wacom: add USB_HID dependency
Date: Fri, 28 Jul 2017 16:18:19 +0200
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References: <20170728131826.180483-1-arnd@arndb.de> <6C9C978F-447D-42A5-9245-894577F2944D@gmail.com>
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To: Jason Gerecke <killertofu@gmail.com>
Cc: Jiri Kosina <jikos@kernel.org>, Jason Gerecke <jason.gerecke@wacom.com>, Benjamin Tissoires <benjamin.tissoires@redhat.com>, "open list:HID CORE LAYER" <linux-input@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Fri, Jul 28, 2017 at 4:07 PM, Jason Gerecke <killertofu@gmail.com> wrote:
> On July 28, 2017 6:18:00 AM PDT, Arnd Bergmann <arnd@arndb.de> wrote:
>>The driver has gained a compile-time dependency that we should
>>express in Kconfig to avoid this link error:
>>
>
> Would conditional compilation be an acceptable alternative to adding
> a dependency? The USB_HID code is only used to check if the driver
> is working with a USB device. With USB_HID disabled, there's no need
> for the check so there's no need for the dependency.

I think that should work, e.g. you could replace the hid_is_using_ll_driver
and 'extern' defintions with a helper per ll-driver like

#ifdef CONFIG_USB_HID
extern bool hid_is_using_usb_driver(struct hid_device *hdev)
#else
static inline bool hid_is_using_usb_driver(struct hid_device *hdev)
{
       return false;
}
#endif

but is it worth it to avoid the dependency?

       Arnd