linux-kernel - Re: [PATCH] ASoC: codecs: use SNDRV_PCM_FMTBIT

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Date:	Tue, 26 May 2015 16:03:17 +0200
From:	"Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:	Takashi Iwai <tiwai@...e.de>
CC:	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	patches@...nsource.wolfsonmicro.com,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Daniel Mack <daniel@...que.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
	Matt Reimer <mreimer@...systems.com>
Subject: Re: [PATCH] ASoC: codecs: use SNDRV_PCM_FMTBIT_* for format bitmask

Hello Takashi,

W dniu 26.05.2015 07:29, Takashi Iwai pisze:
> At Sat, 23 May 2015 18:32:29 +0200,
> Maciej S. Szmigiero wrote:
>>
>> snd_soc_pcm_stream.formats is a bitmask of SNDRV_PCM_FMTBIT_*,
>> not of SNDRV_PCM_FORMAT_* (which are sequential integers),
>> however some of ASoC CODEC drivers use these values instead.
>>
>> Found out by sparse on 0-day kernel tester.
>>
>> Signed-off-by: Maciej Szmigiero <mail@...iej.szmigiero.name>
> 
> Wow, that made me wonder how these drivers could actually work.

Maybe, by coincidence, the wrong defines contained enough bits
set to actually select some common, working format with their
controllers?

> BTW, how did you detect it?  Any static analyzer like sparse or
> smatch?  sparse didn't detect it at the last time I tried, IIRC...

I've received an e-mail from "kbuild test robot" at
"0-DAY kernel test infrastructure" that automated testing there
using sparse found this issue on wm9713 and stac9766 CODECs.

The exact warning was:
>> sound/soc/codecs/stac9766.c:324:28: sparse: incorrect type in initializer (different base types)
   sound/soc/codecs/stac9766.c:324:28:    expected unsigned long long [unsigned] [usertype] formats
   sound/soc/codecs/stac9766.c:324:28:    got restricted snd_pcm_format_t [usertype] <noident>

What is important the warning doesn't show unless a check build
is made with CF=-D__CHECK_ENDIAN__ .

Upon checking I've found the same issue also in two other CODECs,
which aren't normally being built on x86_64 (target architecture
for above automated build) even when SND_SOC_ALL_CODECS is selected.

> thanks,
> 
> Takashi

Best regards,
Maciej Szmigiero

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