linux-kernel - Re: [PATCH] sound: hdmi: avoid dereferencing uninitialized 'jack' pointer

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Date:	Tue, 16 Feb 2016 17:09:43 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Takashi Iwai <tiwai@...e.de>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org, Jaroslav Kysela <perex@...ex.cz>,
	Mark Brown <broonie@...nel.org>, Han Lu <han.lu@...el.com>,
	Libin Yang <libin.yang@...ux.intel.com>,
	Thierry Reding <treding@...dia.com>,
	David Henningsson <david.henningsson@...onical.com>
Subject: Re: [PATCH] sound: hdmi: avoid dereferencing uninitialized 'jack' pointer

On Tuesday 16 February 2016 16:49:42 Takashi Iwai wrote:
> 
> Thanks for the patch.  But I think it's cleaner to fix Kconfig.
> 
> Thinking more of it, maybe splitting jack stuff as a separate module
> and does reverse-select to CONFIG_INPUT would be better.  Then its
> users can select simply SND_JACK, and everything would fit.
> 
> 

Adding 'select INPUT' is rather nasty, I think that can lead to circular
dependencies, and would likely upset users of small embedded systems
that want to use audio but don't want to use input.

Generally speaking, I would recommend never using 'select' on a user
visible Kconfig symbol.

Another option might would be to change snd_jack_new() to return
an error if that SND_JACK is disabled, and then require all users
to handle the error gracefully, i.e. not fail the probe() function
but just not use the jack.

	Arnd