linux-kernel - Re: wl1251 & mac address & calibration data

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Date:   Thu, 24 Nov 2016 17:08:30 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Pavel Machek <pavel@....cz>,
        Michal Kazior <michal.kazior@...to.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Tony Lindgren <tony@...mide.com>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: wl1251 & mac address & calibration data

Hi,

On Thu, Nov 24, 2016 at 04:20:45PM +0100, Pali Rohár wrote:
> On Thursday 24 November 2016 16:13:17 Sebastian Reichel wrote:
> > On Thu, Nov 24, 2016 at 09:33:29AM +0100, Pali Rohár wrote:
> > > On Thursday 24 November 2016 08:51:04 Pavel Machek wrote:
> > > > > > "ifconfig hw ether XX" normally sets the address. I guess that's
> > > > > > ioctl?
> > > > > 
> > > > > This sets temporary address and it is ioctl. IIRC same as what ethtool 
> > > > > uses. (ifconfig is already deprecated).
> > > > > 
> > > > > > And I guess we should use similar mechanism for permanent
> > > > > > address.
> > > > > 
> > > > > I'm not sure here... Above ioctl ↑↑↑ is for changing temporary mac 
> > > > > address. But here we do not want to change permanent mac address. We 
> > > > > want to tell kernel driver current permanent mac address which is
> > > > > stored
> > > > 
> > > > Well... I'd still use similar mechanism :-).
> > > 
> > > Thats problematic, because in time when wlan0 interface is registered
> > > into system and visible in ifconfig output it already needs to have
> > > permanent mac address assigned.
> > > 
> > > We should assign permanent mac address before wlan0 of wl1251 is
> > > registered into system.
> > 
> > You can just add the MAC address to the NVS data, which is also
> > required for the device initialization.
> 
> NVS data file has fixed size, there is IIRC no place for it.
> 
> But one of my suggestion was to use another request_firmware for MAC
> address. So this is similar to what you are proposing, as NVS data are
> loaded by request_firmware too...

Just append it to NVS data and modify the size check accordingly?

> > I wonder if those information could be put into DT. Iirc some
> > network devices get their MAC address from DT. Maybe we can add
> > all NVS info to DT? How much data is it?
> 
> Proprietary, signed and closed bootloader NOLO does not support DT. So
> for booting you need to append DTS file to kernel image.

Yeah, so NOLO without U-Boot will depend on userspace to fixup DT.

> U-Boot is optional and can be used as intermediate bootloader between
> NOLO and kernel. But still it has problems with reading from nand, so
> cannot read NVS data nor MAC address.

It may in the future?

> > Userspace application can add all those information to the DT
> > using a DT overlay. Also the u-boot could parse and add it at
> > some point in the future.
> 
> In case when wl1251 is statically linked into kernel image, it is loaded
> and initialized before even userspace applications starts.
>
> So no... adding NVS data or MAC address into DT or DT overlay is not a
> solution.

Actually with data loaded from DT you *can* load data quite early in
the boot process, while your suggestions always require userspace.
So you argument against yourself?

-- Sebastian

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