linux-kernel - RE: [PATCH] ASoC: Augment existing card DAPM routes in snd_soc_of_parse_audio

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Message-ID: <c837f8c59be24429aeed270636aac570@EMAIL.axentia.se>
Date:	Fri, 28 Nov 2014 16:11:13 +0000
From:	Peter Rosin <peda@...ntia.se>
To:	Mark Brown <broonie@...nel.org>, Peter Rosin <peda@...ator.liu.se>
CC:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ASoC: Augment existing card DAPM routes in
 snd_soc_of_parse_audio_routing

Mark Brown wrote:
> On Thu, Nov 27, 2014 at 10:02:42PM +0100, Peter Rosin wrote:
> 
> > -	routes = devm_kzalloc(card->dev, num_routes * sizeof(*routes),
> > +	old_routes = card->num_dapm_routes;
> > +	routes = devm_kzalloc(card->dev,
> > +			      (old_routes + num_routes) * sizeof(*routes),
> >  			      GFP_KERNEL);
> >  	if (!routes) {
> >  		dev_err(card->dev,
> > @@ -4611,9 +4613,11 @@ int snd_soc_of_parse_audio_routing(struct
> snd_soc_card *card,
> >  		return -EINVAL;
> >  	}
> >
> > +	memcpy(routes, card->dapm_routes, old_routes * sizeof(*routes));
> > +
> 
> Aren't we open coding krealloc() here?

I don't think krealloc() is appropriate since we don't know where the memory
comes from. The typical use I see is that the card struct is initialized as:

static const struct snd_soc_dapm_route foo_intercon[] = {
	{ "MUX1", "Loop", "IN1" },
	{ "MUX1", "Mixer", "MIX1" },

	{ "MIX1", NULL, "DAC" },
	{ "MIX1", "IN1 Switch", "IN1" },

	{ "Line Out Jack", NULL, "MUX1" },
};

static struct snd_soc_card foo_card = {
	.name = "foo",
	.owner = THIS_MODULE,
	.dapm_routes = foo_intercon,
	.num_dapm_routes = ARRAY_SIZE(foo_intercon),
	/* etc */
};

If that's the case, krealloc() seems dead wrong. On the other hand, if
snd_soc_of_parse_audio_routing() were to be called many times, a lot
of devm_kzalloc()ed memory would be kept dangling. I don't expect a card
to call snd_soc_of_parse_audio_routing() more than once though...

Cheers,
Peter

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