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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc:     Felix Fietkau <nbd@nbd.name>, ath9k-devel@qca.qualcomm.com,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ath9k: turn on btcoex_enable as default
References: <20180208052801.15670-1-kai.heng.feng@canonical.com>
        <56d650e6-d26f-087c-4e86-2e5d4e859414@nbd.name>
        <A5972CE9-8325-404A-A63D-ED29E44FB67B@canonical.com>
        <87k1vmeip8.fsf@kamboji.qca.qualcomm.com>
        <E500FA42-23F1-433F-9BFB-78A2FD1946AF@canonical.com>
        <7170e2d5-a59d-8260-fa8e-f02f583b773f@nbd.name>
        <6A0F65EF-A7C4-469F-8FAF-CBE314676237@canonical.com>
        <9AF82E83-2EBE-4076-BAFA-EEA44B1DB423@canonical.com>
Date:   Thu, 23 Aug 2018 14:18:10 +0300
In-Reply-To: <9AF82E83-2EBE-4076-BAFA-EEA44B1DB423@canonical.com> (Kai-Heng
        Feng's message of "Thu, 23 Aug 2018 09:33:56 +0800")
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Kai-Heng Feng <kai.heng.feng@canonical.com> writes:

> at 12:15, Kai Heng Feng <kai.heng.feng@canonical.com> wrote:
>
>>
>>
>>> On 10 Feb 2018, at 10:05 PM, Felix Fietkau <nbd@nbd.name> wrote:
>>>
>>> On 2018-02-10 14:56, Kai Heng Feng wrote:
>>>>> On 9 Feb 2018, at 3:16 PM, Kalle Valo <kvalo@codeaurora.org> wrote:
>>>>> Sure, but we have to make sure that we don't create regressions on
>>>>> existing systems. For example, did you test this with any system which
>>>>> don't support btcoex? (just asking, haven't tested this myself)
>>>>
>>>> No not really, but I will definitely test it.
>>>> The only module I have that uses ath9k is Dell=E2=80=99s DW1707.
>>>> How do I check if it support btcoex or not?
>>> I just reviewed the code again, and I am sure that we cannot merge this
>>> patch. Enabling the btcoex parameter makes the driver enable a whole
>>> bunch of code starting timers, listening to some GPIOs, etc.
>>>
>>> On non-btcoex systems, some of those GPIOs might be floating or even
>>> connected to different things, which could cause a lot of undefined
>>> behavior.
>>>
>>> This is simply too big a risk, so there absolutely needs to be a
>>> whitelist for systems that need this, otherwise it has to remain
>>> disabled by default.
>>
>> So what information can we use to whitelist btcoex chips?
>> Can we get btcoex support status at ath9k probing?
>
> Sorry for bringing this up again.
>
> Is DMI based match an acceptable approach for ath9k?

I don't know what Felix thinkgs, but to me using DMI sounds like a good
idea to try, assuming the matches are unique enough and there's no risk
of enabling bt coex on wrong platforms. Should the PCI bus number etc
checked as well in case the user adds more ath9k devices to the
platform?

But of course I need to see the patch to comment more.

--=20
Kalle Valo