linux-kernel - Re: [PATCH v3 2/2] usb: dwc2: add 'mode' which based on Kconfig select or dts setting

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Date:	Wed, 6 Aug 2014 15:13:35 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Paul Zimmerman <Paul.Zimmerman@...opsys.com>
Cc:	Kever Yang <kever.yang@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Addy Ke <addy.ke@...k-chips.com>,
	Eddie Cai <cf@...k-chips.com>, Jianqun Xu <xjq@...k-chips.com>,
	Olof Johansson <olof@...om.net>,
	Sonny Rao <sonnyrao@...omium.org>, wulf <wulf@...k-chips.com>,
	lyz <lyz@...k-chips.com>, Jingoo Han <jg1.han@...sung.com>,
	han jiang <hj@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] usb: dwc2: add 'mode' which based on Kconfig
 select or dts setting

Paul,

On Tue, Aug 5, 2014 at 1:08 PM, Paul Zimmerman
<Paul.Zimmerman@...opsys.com> wrote:
>> Maybe dwc2 is refer to the Kconfig in dwc3 for there is a choice from
>> one of "Host only mode", "Gadget only mode" and "Dual Role mode",
>> which means the role is decided by the Kconfig.
>>
>> In my opinion, there maybe more than one controller in a Soc, and for
>> different
>> usage, the mode select should not be done in Kconfig, it's better to do that
>> in dts file.
>> I agree with you that the CONFIG_USB_DWC2_HOST should defined for host
>> functionality, not for role definition.
>>
>> Paul: what do you think?
>
> I'm confused about how your dual-role mode implementation is supposed
> to work. Right now, the host and peripheral modes are compiled as
> separate drivers, and there is no dual-role mode in the Kconfig. So I
> don't see how your code can work. Have you tested it?

Ah, interesting.  I just assumed that since you could compile both in
that dual mode was there, but I clearly was confused.

I don't think Kever had tested dual_role mode.


> Dinh Nguyen is working on a patch series to add dual-role support, I
> think you have seen that, right? That adds the Kconfig options for all
> three modes. Maybe you should build on top of that?

I hadn't personally seen it, but now I have!  I guess this is the
newest <https://www.mail-archive.com/linux-usb@vger.kernel.org/msg46103.html>.

I haven't done a thorough review, but I think Kever's patch v4
<https://patchwork.kernel.org/patch/4682711/> is still relevant since
I don't see anything parsing the dr_mode in Dinh's patches.

-Doug
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