linux-kernel - Re: [cfg80211 / iwlwifi] setting wireless regulatory domain doesn't work.

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Date:	Wed, 18 Dec 2013 11:48:45 +0100
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Johannes Berg <johannes@...solutions.net>
CC:	Arend van Spriel <arend@...adcom.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ben Hutchings <ben@...adent.org.uk>,
	Julian Calaby <julian.calaby@...il.com>,
	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ilw@...ux.intel.com" <ilw@...ux.intel.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"John W. Linville" <linville@...driver.com>,
	Avinash Patil <avinashapatil@...il.com>
Subject: Re: [cfg80211 / iwlwifi] setting wireless regulatory domain doesn't work.


Wednesday, December 18, 2013, 10:26:25 AM, you wrote:

> Hi all,

> We really should be asking Luis to look at this who hasn't yet chimed
> in, presumably because he's between jobs (and travelling IIRC)

> On Wed, 2013-12-18 at 10:16 +0100, Arend van Spriel wrote:
>> On 12/17/2013 11:06 PM, Linus Torvalds wrote:
>> > We have literally had this *exact* same issue with firmware loading.
>> > Network drivers shouldn't try to load firmware at module load time.
>> > Same deal.
>> 
>> It is kind of a chicken and egg problem for (wireless) networking
>> drivers. To get IFF_UP from the network layer you have to register a
>> netdevice. For wireless drivers this means you have to register a wiphy
>> device with cfg80211 which flags capabilities and optionally are custom
>> regulatory domain. That information depends on the device and firmware
>> used. And there we have a full circle.

> This is all really beside the point.

> For this CRDA information, the kernel never actually *waits* for it, so
> in the case that there's no reply, it uses the built-in world domain. So
> it's not like request_firmware(), which will block boot forever, but
> it's also not like request_firmware_nowait() which will eventually time
> out and come back with an error if userspace isn't handling it (though
> now that firmware loading is built in ...)

> The issue is that it uses the built-in data *forever*, and what Sander
> said was "or it will block forever" but just meant that it never was
> able to do any further updates.

> It *doesn't* actually block the boot process or such. Everything Linus
> said is true but seems to have been written in understanding "blocks" as
> "blocking the boot process", rather than "blocking further updates".

> Regardless of this, even blocking further updates is a really bad idea.
> There are a few ways to handle this, but I'll let Luis poke at that.

Your description is correct, sorry if I was not clear.

--
Sander

> johannes



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