Message-ID: <5550AE7C.6050208@collabora.co.uk>
Date:	Mon, 11 May 2015 15:28:28 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Michal Suchanek <hramrach@...il.com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Lukasz Majewski <l.majewski@...sung.com>,
	Andreas Faerber <afaerber@...e.de>,
	Sachin Kamat <sachin.kamat@...sung.com>,
	Sjoerd Simons <sjoerd.simons@...labora.co.uk>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-samsung-soc@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: exynos_defconfig: add options to make wifi usable

On 05/11/2015 02:23 PM, Michal Suchanek wrote:
> On 11 May 2015 at 13:25, Javier Martinez Canillas
> <javier.martinez@...labora.co.uk> wrote:
>> Hello Michal,
>>
>> On 05/11/2015 12:22 PM, Michal Suchanek wrote:
>>> The Exynos defconfig includes mwifiex sdio support which is present on
>>> some of the Exynos boards.
>>>
>>> For the WiFi to be usable two extra options are needed. Usermode
>>
>> Your subject line and the commit message are somehow misleading since
>> these options are needed to make the WiFi usable with your current setup.
>>
>>> firmware helper to load out-of-kernel firmware and wireless extensions
>>
>> For example, this is only needed if the in-kernel fw loader is not
>> able to find the firmware but isn't needed if the fw is for example
>> in an initial ramdisk and the kernel is able to load it, built in the
>> kernel or if the mwifiex driver is built as a module.
> 
> I am not sure how is including the firmware in a ramdisk going to
> improve things over including it in my root filesystem. As far as I am
> aware it does not make any difference for the kernel.
> 

My understanding is that an initial ramdisk is mounted very early in the
kernel boot process so even a module-less initamfs that only contains a
set of firmwares is enough to make the request_firmware() of built in
drivers to succeed.

While having those in your root filesystem located in a storage media,
will make the request_firmware() to fail since the rootfs is mounted much
later after built in drivers' probe functions have already been executed.

But now you make me doubt if I'm wrong on my assumptions and I should
check if that's the case.

> The firmware is not included in the kernel tree nor configured as
> extra firmware option in the defconfig, either. Otherwise the firmware
> loader would supposedly find the firmware and we would not have this
> discussion.
> 
> The mwifiex driver is configured as built-in in the defconfig so what
> happens when the driver is built as a module is not relevant for this
> defconfig.
>

Yes, these two (fw built-in the kernel and driver as a module) were just
other examples of setups that don't require the fallback user-mode helper.

At least I would mention in the commit message that given the driver is
built-in, no fw is built-in the kernel couldn't be assumed that a initram
fs will be used, it is better to enable the user-space fw loading fallback.

>>
>>> so the interface can be configured with wireless-tools.
>>>
>>
>> And wireless extensions is deprecated AFAIK and is only needed for old
>> user-space since most tools should had been converted to use the netlink
>> based CONFIG_CFG80211 interface instead.
>>
>> I'm booting a debian jessie and have WiFi working without CFG80211_WEXT
>> for example.
> 
> I'm booting Debian Jessie as well and for me WiFi is not working
> without CFG80211_WEXT for another example.
> 
> So it might be that some tools have migrated to another interface but
> at first glance I have no idea what those tools might be in Debian so
> for me the WiFi is unusable without wireless extensions.
>

I'm using the iw package [0] which according to the package description:

"will become the canonical command line tool for wireless configuration
and iwconfig/wireless-tools will no longer be required"

So I guess iw uses the new netlink based interface while wireless-tools
is still using the old ioctl based API.

That's something that could also be mentioned in the commit message.

>>
>> That doesn't mean that I'm against your patch (I'm always happy to enable
>> more config options if that makes the defconfig more useful) but the commit
>> message should be accurate about why a change has to be done.
> 
> Do you have some specific suggestions about improvements to the commit message?
>

I already mentioned them above. My point is that the subject and commit message
said that WiFi is unusable without these options and that's not the case for all
the setups.

> Thanks
> 
> Michal
>

Best regards,
Javier

[0]: https://packages.debian.org/jessie/iw
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