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

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Message-ID: <CA+BoTQkSOJ85PiT=pjmH234sviCj-LVWWM=64KbCe4AG9CMNUg@mail.gmail.com>
Date:   Tue, 22 Nov 2016 17:14:28 +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 22 November 2016 at 16:31, Pali Rohár <pali.rohar@...il.com> wrote:
> On Tuesday 22 November 2016 16:22:57 Michal Kazior wrote:
>> 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.
>
> So... wl1251 on Nokia N900 is not alone and this problem is there for
> more drivers and devices. Which means we should come up with some
> generic solution.

This isn't particularly a problem for ath9k/ath10k.

Let me give you more background on ath10k.

ath10k devices can come with caldata and macaddr stored in their
OTP/EEPROM. In that case a generic "template" board file is used.
Userspace doesn't need to do anything special.

Some vendors however decide to use flash partition to store caldata.
In that case ath10k expects userspace to prepare cal-$bus-$devname.bin
files, each for a different radio (you can have multiple radios on a
system).

Now translating this for wl1251 I would expect it should also use
something like wl1251-nvs-sdio-0x0001.bin for devices like N900 that
have caldata on flash partition (instead of the generic
wl1251-nvs.bin). I'm not sure if wl1251-nvs.bin is something
comparable to (the generic) board.bin ath10k has though. Maybe the
entire idea behind wl1251-nvs.bin is flawed as it's supposed to be
device specific and is oblivious to possibility of having multiple
wl1251 radios on one system (probably sane assumption from practical
standpoint but still).


>> >> 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?
>
> Via modprobe hook I can either pass custom module parameter or call any
> other system (shell) commands.
>
> As wl1251.ko does not accept mac_address as module parameter, such
> modprobe hook does not help -- as there is absolutely no way from
> userspace to set or change (permanent) mac address.

Quoting modprobe.d manual:

>       install modulename command...
>           This command instructs modprobe to run your
>           command instead of inserting the module in the
>           kernel as normal. The command can be any shell
>           command: this allows you to do any kind of
>           complex processing you might wish. [...]

You can hook up a script that cooks up wl1251-nvs.bin (caldata,
macaddr) and then insmod the actual wl1251.ko module. Or you can just
cook up the nvs on first device boot and store it in /lib/firmware
(possibly overwriting the "generic" wl1251 from linux-firmware).


Michal