linux-kernel - Re: bluetooth related firmware loader spew on resume.

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Date:	Wed, 26 Nov 2014 11:43:36 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Marcel Holtmann <marcel@...tmann.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	pgynther@...gle.com, linux-bluetooth@...r.kernel.org
Subject: Re: bluetooth related firmware loader spew on resume.

On Wed, 2014-11-26 at 11:31 +0100, Takashi Iwai wrote:
> At Wed, 26 Nov 2014 11:10:23 +0100,
> Oliver Neukum wrote:
> > 
> > On Wed, 2014-11-26 at 09:52 +0100, Takashi Iwai wrote:
> > > At Wed, 26 Nov 2014 14:15:27 +0900,
> > 
> > > In order to paper over this, we may also remember the failing firmware
> > > and avoid loading it.  This might be an easer way than the endless
> > > fight against UMH race...
> > 
> > Hi,
> > 
> > the full fix would be to implement reset_resume() for btusb.
> > It seems to me that setup() should be split in two methods,
> > one to request the firmware from user space and the second
> > to transfer it to the device. reset_resume() would just need
> > to repeat the second operation.
> 
> I'm not against it, but one slight drawback is that you'll have to
> remember the firmware content to transfer by the driver itself in this
> scenario.   In the firmware loader framework, the content is re-read
> at resume so that the largish content isn't kept unnecessarily during
> the whole operation. 

That isn't a drawback but an advantage. Firmware for devices that
do power management needs to be in RAM. The right time to free it
is in disconnect(). But why does that mean that the driver has to
manage the firmware? Can't the firmware layer do it?

You just cannot keep a device operational seamlessly if you request
firmware on resume. We could in theory use a notification queue
running while user space is operational if you really want to save
a little RAM.

	Regards
		Oliver


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