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

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Message-ID: <20170517125335.GG10015@pali>
Date:   Wed, 17 May 2017 14:53:35 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Pavel Machek <pavel@....cz>, Daniel Wagner <wagi@...om.org>,
        Tom Gundersen <teg@...m.no>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        David Gnedt <david.gnedt@...izone.at>,
        Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sre@...nel.org>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Takashi Iwai <tiwai@...e.de>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Grazvydas Ignotas <notasas@...il.com>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org,
        Michał Kazior <kazikcz@...il.com>
Subject: Re: [PATCH 2/6] wl1251: Use request_firmware_prefer_user() for
 loading NVS calibration data

On Wednesday 17 May 2017 14:06:06 Johannes Berg wrote:
> On Tue, 2017-05-16 at 01:13 +0200, Luis R. Rodriguez wrote:
> > > > Now for N900 case there is a similar scenario
> > > > alhtough it has additional requirement to go to user-space due to
> > > > need to use a proprietary library to obtain the NVS calibration
> > > > data. My thought: Why should firmware_class care?
> > 
> > Agreed.
> 
> In fact, why should the *driver* care either? IOW - why should
> "request_firmware_prefer_user()" even exist?

There are default/example NVS data, which are stored in /lib/firmware
and installed by linux-firmware package. Those example calibration data
should not be used for real usage, but Pavel told us that on N900 they
are enough for working WIFI connection. They does not contain valid MAC
address, so kernel should generate some (random?).

So kernel driver should get NVS calibration data from userspace (which
know how where to get or how to prepare them) and in case userspace do
not have it, then we can try fallback to those example data (as people
reported us they can be useful instead of non-working WIFI).

And that fallback is working by direct firmware loading from kernel.

-- 
Pali Rohár
pali.rohar@...il.com