linux-kernel - Re: [PATCH 2/2] ALSA: hda - Deferred probing with request_firmware

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Date:	Thu, 09 Aug 2012 15:32:20 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	David Henningsson <david.henningsson@...onical.com>
Cc:	Thierry Reding <thierry.reding@...onic-design.de>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ALSA: hda - Deferred probing with request_firmware_nowait()

At Thu, 09 Aug 2012 15:26:56 +0200,
David Henningsson wrote:
> 
> On 08/09/2012 03:11 PM, Takashi Iwai wrote:
> 
> > @@ -3187,13 +3217,16 @@ static int __devinit azx_probe(struct pci_dev *pci,
> >   	if (patch[dev] && *patch[dev]) {
> >   		snd_printk(KERN_ERR SFX "Applying patch firmware '%s'\n",
> >   			   patch[dev]);
> > -		err = request_firmware(&chip->fw, patch[dev], &pci->dev);
> > +		err = request_firmware_nowait(THIS_MODULE, true, patch[dev],
> > +					      &pci->dev, GFP_KERNEL, card,
> > +					      azx_firmware_cb);
> >   		if (err < 0)
> >   			goto out_free;
> > +		chip->probe_deferred = 1;
> 
> I might be out on deep water here, but isn't this racy? Or is 
> azx_firmware_cb somehow guaranteed not to execute before this function 
> has exited?

chip->probe_deferred is used only at the line below.
So basically it's not necessarily to be recorded in chip, but could be
a local bool variable in azx_probe().  It remains in chip just because
of my older patch had it.

> 
> >   	}
> >   #endif /* CONFIG_SND_HDA_PATCH_LOADER */
> >
> > -	if (!chip->disabled) {
> > +	if (!chip->disabled && !chip->probe_deferred) {

Here it's checked.


Takashi

> >   		err = azx_probe_continue(chip);
> >   		if (err < 0)
> >   			goto out_free;
> >
> 
> 
> 
> -- 
> David Henningsson, Canonical Ltd.
> https://launchpad.net/~diwic
> 
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