linux-kernel - Re: wl1251 & mac address & calibration data

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Date:   Tue, 22 Nov 2016 16:22:57 +0100
From:   Michal Kazior <michal.kazior@...to.com>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>, Pavel Machek <pavel@....cz>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Tony Lindgren <tony@...mide.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: wl1251 & mac address & calibration data

On 21 November 2016 at 16:51, Pali Rohár <pali.rohar@...il.com> wrote:
> On Friday 11 November 2016 18:20:50 Pali Rohár wrote:
>> Hi! I will open discussion about mac address and calibration data for
>> wl1251 wireless chip again...
>>
>> Problem: Mac address & calibration data for wl1251 chip on Nokia N900
>> are stored on second nand partition (mtd1) in special proprietary format
>> which is used only for Nokia N900 (probably on N8x0 and N9 too).
>> Wireless driver wl1251.ko cannot work without mac address and
>> calibration data.

Same problem applies to some ath9k/ath10k supported routers. Some even
carry mac address as implicit offset from ethernet mac address. As far
as I understand OpenWRT cooks cal blobs on first boot prior to loading
modules.


>> Absence of mac address cause that driver generates random mac address at
>> every kernel boot which has couple of problems (unstable identifier of
>> wireless device due to udev permanent storage rules; unpredictable
>> behaviour for dhcp mac address assignment, mac address filtering, ...).
>>
>> Currently there is no way to set (permanent) mac address for network
>> interface from userspace. And it does not make sense to implement in
>> linux kernel large parser for proprietary format of second nand
>> partition where is mac address stored only for one device -- Nokia N900.
>>
>> Driver wl1251.ko loads calibration data via request_firmware() for file
>> wl1251-nvs.bin. There are some "example" calibration file in linux-
>> firmware repository, but it is not suitable for normal usage as real
>> calibration data are per-device specific.

You could hook up a script that cooks up the cal/mac file via
modprobe's install hook, no?


Michał