netdev - Re: wl1251: NVS firmware data

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Message-ID: <20141206124954.GB17289@amd>
Date:	Sat, 6 Dec 2014 13:49:54 +0100
From:	Pavel Machek <pavel@....cz>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	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>,
	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 Thu 2014-11-27 07:58:40, Greg Kroah-Hartman wrote:
> On Thu, Nov 27, 2014 at 04:22:58PM +0100, Pali Rohár wrote:
> > 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.
> 
> Then you need a dynamic program that you control, in userspace, to dump
> the needed data into the kernel.  Don't try to do it with "static"
> firmware files.  Use the binary sysfs file interface for this if you
> want.

Actually, this seems to be similar situation to fpga programming.

There, it is static firmware for 90% users, but some special use cases
want it more dynamic.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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