netdev - Re: wl1251: NVS firmware data

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Message-Id: <201411271622.58916@pali>
Date:	Thu, 27 Nov 2014 16:22:58 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc:	Ming Lei <ming.lei@...onical.com>,
	"John W. Linville" <linville@...driver.com>,
	Grazvydas Ignotas <notasas@...il.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Kalle Valo <kvalo@...rom.com>,
	Sebastian Reichel <sre@...g0.de>,
	David Gnedt <david.gnedt@...izone.at>
Subject: Re: wl1251: NVS firmware data

On Thursday 27 November 2014 16:16:55 Greg Kroah-Hartman wrote:
> On Thu, Nov 27, 2014 at 03:43:23PM +0100, Pali Rohár wrote:
> > On Thursday 27 November 2014 15:21:44 Ming Lei wrote:
> > > On Thu, Nov 27, 2014 at 10:06 PM, Pali Rohár
> > 
> > <pali.rohar@...il.com> wrote:
> > > > Hello,
> > > > 
> > > > wifi driver wl1251 needs NVS calibration data for
> > > > working. These data are loaded by driver via
> > > > request_firmware from userspace file:
> > > > ti-connectivity/wl1251-nvs.bin. In linux-fimrware git
> > > > tree there is generic wl1251-nvs.bin file which is used
> > > > by default.
> > > > 
> > > > Driver wl1251 is used on Nokia N900 cellphone for its
> > > > wifi chip. This cellphone has one special MTD partition
> > > > (called CAL) where are stored some configuration data
> > > > in special binary (key-value) format. And there is also
> > > > stored correct calibration data for specific device
> > > > (each device has different data). It is preferred to
> > > > use those data instead generic one (provided by
> > > > linux-firmware git tree).
> > > > 
> > > > Now my question is: How to correctly load calibration
> > > > data from special Nokia N900 CAL partition into wl1251
> > > > kernel driver?
> > > 
> > > It is better to let user space script handle the request.
> > 
> > Yes, this makes sense. Implementing CAL parser in kernel
> > wl1251 driver would be hard...
> > 
> > > > By default kernel reads ti-connectivity/wl1251-nvs.bin
> > > > file from VFS if exists without any userspace support.
> > > > If it fails then it fallback to loading via udev.
> > > 
> > > You can remove or rename this file so that loading from
> > > user space can be triggered.
> > 
> > It is no so easy... In case when CAL does not contains NVS
> > data then we want to use this generic NVS file. And telling
> > everybody to rename this is file is not good solution...
> 
> But that's up to your system configuration, not the kernel. 
> Make a userspace package for the firmware that creates it in
> the format you need it to be in, for the hardware you have,
> and then there would not be any need for a kernel change,
> right?
> 
> greg k-h

Not so simple as you think. Some parts of NVS data are configured 
based on location and cellular station. Data are not static.

-- 
Pali Rohár
pali.rohar@...il.com

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