netdev - Re: wl1251 & mac address & calibration data

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Message-ID: <20161121155153.GM13735@pali>
Date:   Mon, 21 Nov 2016 16:51:53 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     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>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: wl1251 & mac address & calibration data

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.
> 
> 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.
> 
> So questions are:
> 
> 1) How to set mac address from userspace for that wl1251 interface? In 
> userspace I can write parser for that proprietary format of nand 
> partition and extract mac address from it

Proposed solutions for 1)

* Introduce new IOCL for setting that permanent mac address from
  userspace. Currently we have IOCL for get request

* Use request_firmware() (with flag from 2)) to ask for mac address from
  userspace. This is already used by wl12xx driver (as mac address is
  part of calibration data firmware file)

* Allow to set mac address via sysfs file, e.g.
  /sys/class/ieee80211/phy0/macaddress

> 2) How to send calibration data to wl1251 driver? Those are again stored 
> in proprietary format and I can write userspace parser for it.

Proposed solution for 2)

Introduce new flag for request_firmware(), so it first try to use
userspace helper for loading firmware file with possibility to fallback
to direct VFS access.


So... what do you think about it?

-- 
Pali Rohár
pali.rohar@...il.com