linux-kernel - Re: will these methods work with firmware loading?

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Date:	Mon, 20 Feb 2012 10:46:07 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	driverdevel <devel@...verdev.osuosl.org>,
	wireless <linux-wireless@...r.kernel.org>,
	linux-hotplug@...r.kernel.org
Subject: Re: will these methods work with firmware loading?

Hi Larry,

> I know that changing the request_firmware() call to request_firmware_nowait() 
> solves the problem; however, that gives some trouble for driver b43legacy as it 
> loads 3 or 4 firmware files depending on the hardware version. When I launch the 
> 3 or 4 nowait requests, I get an error because the system is trying to start 
> several tasks with the same name.
> 
> Would it be OK to load the first file with the nowait version, and issue a 
> request_firmware() for the others from the callback routine? I think that would 
> not cause any problems, but I would like to get confirmation from an expert.

That should work -- I just looked at the firmware code and it spawns a
new thread for every "nowait" request (and it calls the callback in that
thread's context), so it won't block against itself.

> Similarly, if I were to create a work queue, init and schedule it from 
> module_init(), and then use synchronous loads to get the firmware from the work 
> queue callback, would that get around the boot problem? I know it works as I 
> have trial patches; however, my version of udev is not one affected. This method 
> is very easy to implement, but again I would like confirmation from an expert.

We discussed that before, and technically it should work, I'm just a bit
worried about udev treating asynchronous and synchronous requests
differently and that causing issues, but somebody who knows udev better
will have to comment on that.

johannes

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