linux-kernel - Re: [PATCH v7 0/4] usb/gadget: independent registration of gadgets and gadget drivers

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Message-id: <566A9956.7060001@samsung.com>
Date:	Fri, 11 Dec 2015 10:37:26 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Felipe Balbi <balbi@...com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Ruslan Bilovol <ruslan.bilovol@...il.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v7 0/4] usb/gadget: independent registration of gadgets and
 gadget drivers

Hello,

On 2015-12-10 18:13, Felipe Balbi wrote:
> Felipe Balbi <balbi@...com> writes:
>> Felipe Balbi <balbi@...com> writes:
>>> Marek Szyprowski <m.szyprowski@...sung.com> writes:
>>>> This is a resurrection of the patches initially submitted by Ruslan
>>>> Bilovol in the following thread: https://lkml.org/lkml/2015/6/22/554
>>>>
>>>> The changes since the original submission (v5) includes rebase onto
>>>> latest linux-next branch, simplification of the code requested by Alan
>>>> Stern and Felipe Balbi, removal of a patch, which deleted __init/__exit
>>>> attributes (this change has been already merged) and fixes of the
>>>> checkpatch issues.
>>>>
>>>> This feature is urgently needed, because it is not longer possible to
>>>> use workaround to avoid deferred probe in UDC drivers due to
>>>> not-yet-probed i2c regulator drivers (for more information see
>>>> https://lkml.org/lkml/2015/10/30/374 ).
>>>>
>>>> This patchset has been successfully tested on Odroid XU3 boards with
>>>> DWC3 UDC driver being deferred by missing regulator drivers.
>>> there is one problem with this patchset. If I try to statically link
>>> gadget drivers, only one can be chosen, even though I can enable both
>>> dwc3 and dummy_hcd just fine. And, actually, this brings another
>>> problem. How do we handle systems which have 2 USB peripheral
>>> controllers (say, 2 instances of dwc3) and choose which gadget driver
>>> will bind to which controller ?
>> We also seem to have issues with Kconfig. If I try to make gadget driver
>> built-in, when compiling I'll get asked again if I want gadget drivers
>> built-in.
>>
>> Another one: I just tried dummy_hcd built-in, g_zero built-in, dwc3 as a
>> module. I can never load anything to dwc3 ;-)
> In all fairness, none of these are regressions. Can we agree to look at
> these during v4.5-rc so maybe v4.6 has a final solution ?

IMHO solving all the above issues requires reviving one of the previously
abandoned gadget-bus patch series, i.e.
http://thread.gmane.org/gmane.linux.usb.general/109745

Is this an approach You are interested in?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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