netdev - Re: wl1251 & mac address & calibration data

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Message-ID: <20161122153141.GT13735@pali>
Date:   Tue, 22 Nov 2016 16:31:41 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Michal Kazior <michal.kazior@...to.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 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.

> >> 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.

-- 
Pali Rohár
pali.rohar@...il.com