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

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Message-ID: <8737fzrb36.fsf@kamboji.qca.qualcomm.com>
Date:   Tue, 31 Jan 2017 08:35:09 +0200
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Pavel Machek <pavel@....cz>,
        Pali Rohár <pali.rohar@...il.com>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        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>,
        Sebastian Reichel <sre@...nel.org>,
        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

Tony Lindgren <tony@...mide.com> writes:

> * Pavel Machek <pavel@....cz> [170127 11:41]:
>> On Fri 2017-01-27 17:23:07, Kalle Valo wrote:
>> > Pali Rohár <pali.rohar@...il.com> writes:
>> > 
>> > > On Friday 27 January 2017 14:26:22 Kalle Valo wrote:
>> > >> Pali Rohár <pali.rohar@...il.com> writes:
>> > >> 
>> > >> > 2) It was already tested that example NVS data can be used for N900 e.g.
>> > >> > for SSH connection. If real correct data are not available it is better
>> > >> > to use at least those example (and probably log warning message) so user
>> > >> > can connect via SSH and start investigating where is problem.
>> > >> 
>> > >> I disagree. Allowing default calibration data to be used can be
>> > >> unnoticed by user and left her wondering why wifi works so badly.
>> > >
>> > > So there are only two options:
>> > >
>> > > 1) Disallow it and so these users will have non-working wifi.
>> > >
>> > > 2) Allow those data to be used as fallback mechanism.
>> > >
>> > > And personally I'm against 1) because it will break wifi support for
>> > > *all* Nokia N900 devices right now.
>> > 
>> > All two of them? :)
>> 
>> Umm. You clearly want a flock of angry penguins at your doorsteps :-).
>
> Well this silly issue of symlinking and renaming nvs files in a standard
> Linux distro was also hitting me on various devices with wl12xx/wl18xx
> trying to use the same rootfs.
>
> Why don't we just set a custom compatible property for n900 that then
> picks up some other nvs file instead of the default?

Please don't. An ugly kernel workaround in kernel because of user space
problems is a bad idea. wl1251 should just ask for NVS file from user
space, it shouldn't care if it's a "default" file or something else.
That's a user space policy decision.

Why can't you do something like this:

* rename the NVS file linux-firmware to wl1251-nvs.bin.example

* before distro updates linux-firmware create yours own deb/rpm/whatever
  package "wl1251-firmware" which installs your flavor of nvs file (or
  the user fallback helper if more dynamic functionality is preferred)

-- 
Kalle Valo