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

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Message-ID: <1386703339.30202.19.camel@dcbw.foobar.com>
Date:	Tue, 10 Dec 2013 13:22:19 -0600
From:	Dan Williams <dcbw@...hat.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	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.
> > 
> > Dan
> 
> Maybe another way could be to use request_firmware to load address 
> from userspace... Or what do you think?

That sounds like a great idea to try.  A number of devices either need
stub firmware to read the MAC from EEPROM, or do use request_firmware()
to load firmware before they read the MAC.  You may have to use
request_firmware() synchronously though to ensure that the MAC is read
before registering with mac80211.

Dan


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