linux-kernel - Re: [PATCH] ARM: exynos_defconfig: Enable WiFi-Ex as a module instead built-in

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Date:	Wed, 30 Sep 2015 16:37:41 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org
Cc:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Thierry Reding <treding@...dia.com>,
	Anand Moon <linux.amoon@...il.com>,
	Russell King <linux@....linux.org.uk>,
	linux-samsung-soc@...r.kernel.org,
	Andreas Faerber <afaerber@...e.de>,
	Lukasz Majewski <l.majewski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: exynos_defconfig: Enable WiFi-Ex as a module instead
 built-in

On 30.09.2015 16:22, Javier Martinez Canillas wrote:
> Hello Krzysztof,
> 
> On 09/30/2015 02:36 AM, Krzysztof Kozlowski wrote:
>> On 29.09.2015 21:42, Javier Martinez Canillas wrote:
>>> The Marvell WiFi-Ex driver tries to load a firmware on probe. So if the
>>> driver is built-in and probed before a firmware is available, this is
>>> not loaded and the chip does not work.
>>>
>>> This happens for example if an initramfs isn't used since the driver is
>>> probed before the root filesystem is mounted.
>>>
>>> Change the default config since the driver isn't needed for machines to
>>> boot and is more convenient to have it enabled as a module to avoid
>>> requiring an initramfs or to have the firmware built into the kernel.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
>>>
>>> ---
>>>
>>>  arch/arm/configs/exynos_defconfig | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> The user-space can always initiate re-probing of device - just re-bind
> 
> It is true that you can force a re-probing from user-space by doing:
> 
> $ echo "mmc2:0001:1" > /sys/bus/sdio/drivers/mwifiex_sdio/unbind
> $ echo "mmc2:0001:1" > /sys/bus/sdio/drivers/mwifiex_sdio/bind

I suppose the unbind won't be needed, because device aborted the
probe... so only one another bind.

> 
> but:
> 
> a) This is not obvious. In fact, I didn't think that possibility
> before you mentioned and I've been using Linux for many years :)

Eh, questionable. Obvious for me :)

> 
> b) This is not something that isn't done automatically by init systems.

Right.

> 
> So what users will see is that the driver was probed successfully but
> the firmware fails to load later (since the driver users the async
> request_firmware_nowait function to request the firmware).

Okay.

> 
>> it. However I assume that driver cannot work without firmware?
>>
> 
> Yes, it doesn't. I explained this in the commit message. Do you
> think it should be made more clear?

No, its OK, I agree.

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Best regards,
Krzysztof
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