Subject: Re: [PATCH v2 0/1] rtl8xxxu (mac80211) driver for
 rtl8188[cr]u/rtl8192cu/rtl8723au
To: Kalle Valo <kvalo@codeaurora.org>
References: <1440968574-29490-1-git-send-email-Jes.Sorensen@redhat.com>
 <87y4gjfw10.fsf@kamboji.qca.qualcomm.com> <55EC71DB.7060007@lwfinger.net>
 <87d1xufvio.fsf@kamboji.qca.qualcomm.com>
Cc: Jes.Sorensen@redhat.com, linux-wireless@vger.kernel.org
From: Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <55EDAEC9.701@lwfinger.net> (sfid-20150907_173553_906977_4557AAF9)
Date: Mon, 7 Sep 2015 10:35:37 -0500
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Sender: linux-wireless-owner@vger.kernel.org

On 09/07/2015 04:06 AM, Kalle Valo wrote:
> Larry Finger <Larry.Finger@lwfinger.net> writes:
>
>> On 09/06/2015 09:43 AM, Kalle Valo wrote:
>>> Jes.Sorensen@redhat.com writes:
>>>
>>>> Per default only devices I have actually tested will be enabled. If
>>>> you are interested in trying it out with other 8188cu/8188ru/819[12]cu
>>>> dongles, you need to enable CONFIG_RTL8XXXU_UNTESTED. Please report
>>>> test results back to me.
>>>>
>>>> Note if you enable this driver, it may clash with CONFIG_RTL8192U,
>>>> CONFIG_R8723AU, and CONFIG_RTL8192CU (rtlwifi). Please pay attention
>>>> to which module you load and/or use modprobe blacklists.
>>>
>>> May clash? So how does this work in practise? Is the clash referring
>>> CONFIG_RTL8XXXU_UNTESTED enabled or disabled?
>>>
>>> I think we should only have one driver automatically supporting certain
>>> hardware, and not have a driver randomly chosen and forcing users to use
>>> a blacklist.
>>
>> I agree, in principle, but there will be difficulties in the
>> implementation, at least in the short term.
>>
>> At the moment, the only driver that has a conflict with rtl8xxxu is
>> rtl8192cu. Although rtl8xxxu is surprisingly more stable that
>> rtl8192cu, the latter has more features, which is may be the reason
>> for better stability. Driver rtl8xxxu does not handle any 40 MHz
>> channels, nor can it become an AP either with hostapd or with
>> NetworkManager. For those reasons, rtl819cu has to remain the standard
>> driver for RTL81{88,92}CU devices until rtl8xxxu is improved. Anyone
>> that wants to try the new driver will need to use blacklists.
>
> But how do we make sure that for normal users rtl8192cu is always loaded
> and not rtl8xxxu (until we decide to make the switch)? What I'm worried
> is that normal distro users would use rtl8xxxu before it's ready for
> their device.
>
>> We can make changes in the Kconfig help texts that clarify the
>> situation, but that will not help the user of kernels built by the
>> distros.
>
> Exactly. We should not create any regressions to existing setups,
> everything should work as they did before. Kconfig options or blacklist
> tweaking is not an acceptable way to handle that, it should be
> automatic.
>
>>> Also how do we make sure that distros don't enable
>>> CONFIG_RTL8XXXU_UNTESTED? They are notarious of enabling kconfig options
>>> without thinking.
>>
>> It will not necessarily depend on whether CONFIG_RTL8XXXU_UNTESTED is
>> enabled or not. Some of the affected devices are in the tested
>> category.
>
> Ok. Can't we start just rtl8xxxu having just devices NOT supported by
> rtlwifi drivers? All other devices would be under
> CONFIG_RTL8XXXU_UNTESTED until we think the support is ready and we can
> make the switch by moving from untested to tested category. And at the
> same time disable/remove those devices from rtlwifi.

Yes, that will work as long as we make CONFIG_RTL8XXXU_UNTESTED be EXPERIMENTAL 
to keep the distros from enabling it. In addition, a separate GitHub repo for 
rtl8xxxu should be made available with conditional code added to enable builds 
for kernels 3.10 or later. Then users that complain about some problem with 
rtl8192cu can be directed to that driver.

Larry