linux-kernel - Re: [PATCH v2 15/16] wl1251: Add sysfs file address for setting permanent mac address

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Date:	Wed, 11 Dec 2013 21:17:34 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Pali Rohár <pali.rohar@...il.com>
CC:	Dan Williams <dcbw@...hat.com>, Kalle Valo <kvalo@...rom.com>,
	"Luciano Coelho" <luca@...lho.fi>,
	"John W. Linville" <linville@...driver.com>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <freemangordon@....bg>,
	<aaro.koskinen@....fi>, <pavel@....cz>, <sre@...g0.de>,
	<joni.lapilainen@...il.com>,
	Johannes Berg <johannes@...solutions.net>,
	Felipe Contreras <felipe.contreras@...il.com>
Subject: Re: [PATCH v2 15/16] wl1251: Add sysfs file address for setting
 permanent mac address

On Tue, 2013-12-10 at 18:52 +0100, Pali Rohár wrote:
> On Tuesday 10 December 2013 18:49:22 Dan Williams wrote:
> > On Tue, 2013-12-10 at 18:14 +0100, Pali Rohár wrote:
> > > On Tuesday 10 December 2013 17:10:50 Pali Rohár wrote:
> > > > On Tuesday 10 December 2013 16:49:23 Kalle Valo wrote:
> > > > > Pali Rohár <pali.rohar@...il.com> writes:
> > > > > > Driver wl1251 generating mac address randomly at
> > > > > > startup and there is no way to set permanent mac
> > > > > > address via SET_IEEE80211_PERM_ADDR. This patch
> > > > > > export sysfs file which can set permanent mac address
> > > > > > by userspace helper program. Patch is needed for
> > > > > > devices which do not store mac address in internal
> > > > > > wl1251 eeprom.
> > > > > > 
> > > > > > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> > > > > 
> > > > > We have ioctl() command for setting the mac address.
> > > > 
> > > > Really? Is there ioctl for setting permanent mac address?
> > > > Can you show me it?
> > > 
> > > Now I looked at it again and I did not found any ioctl for
> > > it. There is only ioctl cmd for getting address, not
> > > setting it.
> > > 
> > > #define SIOCETHTOOL 0x8946
> > > 
> > > /* Get permanent hardware address */
> > > #define ETHTOOL_GPERMADDR 0x00000020
> > 
> > Yeah, because it's supposed to be permanent and unchanging. 
> > Which means if there was an ioctl for it, that would be
> > contrary to the purpose of a permanent MAC address.
> > 
> > I realize the N900 stores the WiFi MAC address completely
> > differently than many other systems, and that's why this
> > sysfs file was created.  I don't really have a great
> > converged solution for that, other than what you've currently
> > got, or perhaps adding SPERMADDR to ethtool.  One thing I
> > *would* like though, is a restriction on the sysfs file such
> > that if the permanent MAC is already set, it cannot be set
> > again.  Otherwise the permanent MAC address isn't permanent
> > at all.

I'm really uncomfortable with the idea of involving userland in
establishing the 'permanent' MAC address.  (And from what I gather, the
Nokia software never did that but only used SIOCSIFHWADDR.)  It ought to
be set before the interface is ever registered.

> > Dan
> 
> Maybe another way could be to use request_firmware to load address 
> from userspace... Or what do you think?

I think that's an even worse idea.  This is not firmware and it already
exists in separate storage.

I think that rx51_init_wl1251() in
arch/arm/mach-omap2/board-rx51-peripherals.c should either copy the MAC
address out of NVRAM, or if it's too early to do that, then schedule a
function to run later and only then set up wl1251 platform data.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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