linux-kernel - Re: [PATCH] usb: select NOP_USB_XCEIV by drivers that require it

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Date:	Fri, 27 May 2016 07:11:00 +0200
From:	Michal Suchanek <hramrach@...il.com>
To:	Peter Chen <hzpeterchen@...il.com>
Cc:	linux-sunxi <linux-sunxi@...glegroups.com>,
	Peter Chen <Peter.Chen@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bin Liu <b-liu@...com>, Felipe Balbi <balbi@...nel.org>,
	linux-usb <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: select NOP_USB_XCEIV by drivers that require it

On 27 May 2016 at 05:41, Peter Chen <hzpeterchen@...il.com> wrote:
> On Thu, May 26, 2016 at 07:25:23PM -0000, Michal Suchanek wrote:
>> Hello,
>>
>> I was updating my config by make oldconfig for a while and noticed that my USB
>> OTG controller is not working. Apparently it grew dependency on NOP_USB_XCEIV
>> over time.
>>
>> Looking through defconfigs some have it included and some which seem in need of
>> it don't.
>>
>> Since the dependency is not obvious I think it would be better to select it
>> where possible.
>
> From Documentation/kbuild/kconfig-language.txt
>         In general use select only for non-visible symbols
>         (no prompts anywhere) and for symbols with no dependencies.
>
> But NOP_USB_XCEIV is a visible symbol and can be chosen, besides,
> NOP_USB_XCEIV has already selected USB_PHY. Using select may cause
> dependency problem in future, so unless it is necessary, use it
> as least as possible.
>
> If you are using new code, and it adds new dependency code, it is
> reasonable you may need to update your defconfig.

If the driver gets split into multiple parts that need to be
configured separately that's reasonable.

If the newly required option is some obscure feature internal to the
Linux implementation like NOP_USB_XCEIV it's not reasonable in my
book.

Thanks

Michal