linux-kernel - Re: [PATCH 2/6] wl1251: Use request_firmware_prefer

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Date:   Fri, 27 Jan 2017 11:05:32 +0100
From:   Arend Van Spriel <arend.vanspriel@...adcom.com>
To:     Pali Rohár <pali.rohar@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>
Cc:     Ming Lei <ming.lei@...onical.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Gnedt <david.gnedt@...izone.at>,
        Michal Kazior <michal.kazior@...to.com>,
        Daniel Wagner <wagi@...om.org>,
        Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sre@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Grazvydas Ignotas <notasas@...il.com>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/6] wl1251: Use request_firmware_prefer_user() for
 loading NVS calibration data

On 27-1-2017 10:43, Pali Rohár wrote:
> On Friday 27 January 2017 09:33:40 Kalle Valo wrote:
>> Pali Rohár <pali.rohar@...il.com> writes:
>>
>>> NVS calibration data for wl1251 are model specific. Every one device with
>>> wl1251 chip has different and calibrated in factory.
>>>
>>> Not all wl1251 chips have own EEPROM where are calibration data stored. And
>>> in that case there is no "standard" place. Every device has stored them on
>>> different place (some in rootfs file, some in dedicated nand partition,
>>> some in another proprietary structure).
>>>
>>> Kernel wl1251 driver cannot support every one different storage decided by
>>> device manufacture so it will use request_firmware_prefer_user() call for
>>> loading NVS calibration data and userspace helper will be responsible to
>>> prepare correct data.
>>>
>>> In case userspace helper fails request_firmware_prefer_user() still try to
>>> load data file directly from VFS as fallback mechanism.
>>>
>>> On Nokia N900 device which has wl1251 chip, NVS calibration data are stored
>>> in CAL nand partition. CAL is proprietary Nokia key/value format for nand
>>> devices.
>>>
>>> With this patch it is finally possible to load correct model specific NVS
>>> calibration data for Nokia N900.
>>>
>>> Signed-off-by: Pali Rohár <pali.rohar@...il.com>
>>> ---
>>>  drivers/net/wireless/ti/wl1251/Kconfig |    1 +
>>>  drivers/net/wireless/ti/wl1251/main.c  |    2 +-
>>>  2 files changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/wireless/ti/wl1251/Kconfig b/drivers/net/wireless/ti/wl1251/Kconfig
>>> index 7142ccf..affe154 100644
>>> --- a/drivers/net/wireless/ti/wl1251/Kconfig
>>> +++ b/drivers/net/wireless/ti/wl1251/Kconfig
>>> @@ -2,6 +2,7 @@ config WL1251
>>>  	tristate "TI wl1251 driver support"
>>>  	depends on MAC80211
>>>  	select FW_LOADER
>>> +	select FW_LOADER_USER_HELPER
>>>  	select CRC7
>>>  	---help---
>>>  	  This will enable TI wl1251 driver support. The drivers make
>>> diff --git a/drivers/net/wireless/ti/wl1251/main.c b/drivers/net/wireless/ti/wl1251/main.c
>>> index 208f062..24f8866 100644
>>> --- a/drivers/net/wireless/ti/wl1251/main.c
>>> +++ b/drivers/net/wireless/ti/wl1251/main.c
>>> @@ -110,7 +110,7 @@ static int wl1251_fetch_nvs(struct wl1251 *wl)
>>>  	struct device *dev = wiphy_dev(wl->hw->wiphy);
>>>  	int ret;
>>>  
>>> -	ret = request_firmware(&fw, WL1251_NVS_NAME, dev);
>>> +	ret = request_firmware_prefer_user(&fw, WL1251_NVS_NAME, dev);
>>
>> I don't see the need for this. Just remove the default nvs file from
>> filesystem and the fallback user helper will be always used, right?
> 
> It is part of linux-firmware repository. And already part of all
> previous versions of linux-firmware packages in lot of linux
> distributions. So removing it is not possible...

You are probably saying that on your platform you can not remove
anything from /lib/firmware, right? I don't see how you come from "it is
part of firmware package" to "removing is not possible". Trying to
understand this and it makes no sense.

>> Like we discussed earlier, the default nvs file should not be used by
>> normal users.
> 
> But already is and we need to deal with this fact.

Why? Are there other platforms that use the default nvs file and have a
working wifi. So your "removing is not possible" would be about
regression for those?

Regards,
Arend