linux-kernel - RE: [PATCH v2] ASoC: SGTL5000: Fix kernel failed while trying to get optional VDDD supply.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1DD289F6464F0949A2FCA5AA6DC23F828E3D21@039-SN2MPN1-011.039d.mgd.msft.net>
Date:	Tue, 3 Dec 2013 09:49:47 +0000
From:	Li Xiubo <Li.Xiubo@...escale.com>
To:	Mark Brown <broonie@...nel.org>
CC:	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"perex@...ex.cz" <perex@...ex.cz>, "tiwai@...e.de" <tiwai@...e.de>,
	Fabio Estevam <Fabio.Estevam@...escale.com>,
	"LW@...O-electronics.de" <LW@...O-electronics.de>,
	"oskar@...ra.com" <oskar@...ra.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] ASoC: SGTL5000: Fix kernel failed while trying to
 get optional VDDD supply.

> > +static int sgtl5000_external_vddd_used(struct snd_soc_codec *codec) {
> > +	struct regulator *consumer;
> > +	struct sgtl5000_priv *sgtl5000 = snd_soc_codec_get_drvdata(codec);
> > +
> > +	consumer = regulator_get_optional(codec->dev,
> > +			sgtl5000->supplies[VDDD].supply);
> > +	if (IS_ERR(consumer))
> > +		return 0;
> > +
> > +	regulator_put(consumer);
> > +
> > +	return 1;
> > +}
> 
> This is broken with respect to deferred probe, deferred probe returns an
> error when an external regulator is in use but not yet registered.
> The driver needs to at least handle -EPROBE_DEFER specially here.
> 

Well, as we can see that:
1, If the dev has no regulator dt node, a -ENODEV error will be returned. 
2, If the regulator dt node is exist but the optional VDDD is absent (i.e.
The external VDDD is not used), a -EPROBE_DEFER will be returned, if just
return the -EPROBE_DEFER to the probe(and then the probe deferral
mechanism will do the probe again later, is that right ?), and then the
regulator_get_optional() will be called later again, and the -EPROBE_DEFER
will be returned again too, and now how should I handle -EPROBE_DEFER error
twice ? Or should there be a counter about this ? That to say when the
-EPROBE_DEFER error is the second time returned from regulator_get_optional()
can we ensure that the optional VDDD is really not in use.

That's also to say, the regulator_get_optional() must be called twice then
could we know whether the optional external VDDD is really in use or not by
using one counter here.

Or maybe adding a counter in regulator_get_optional() is better.

And do you have any other suggestions to deal with this ?




> It's also not nice to get the regulator, release it and get it again which
> you end up needing to do because...
> 

I have also considered about this. Because if the regulator_bulk_get()
has failed to get the other supplies, the optional one should be released too.
And it can be more easy to deal with.

Yes, this is not very nice and I will revise this.


> > -	ret = regulator_bulk_get(codec->dev, ARRAY_SIZE(sgtl5000->supplies),
> > +	if (sgtl5000_external_vddd_used(codec)) {
> > +		ret = regulator_bulk_get(codec->dev,
> > +				ARRAY_SIZE(sgtl5000->supplies),
> >  				sgtl5000->supplies);
> 
> ...I think my previous comments about this code being poorly structured in
> the existing driver stand.  The bulk get should be used for the supplies
> that are always needed and a separate optional get should be used for this
> one.

Yes, it's.

--
Best Regards,

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/