linux-kernel - Re: [PATCH] ASoC: adau1373: adau1373_hw

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Message-ID: <513DFA55.2050104@canonical.com>
Date:	Mon, 11 Mar 2013 09:37:57 -0600
From:	Tim Gardner <tim.gardner@...onical.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
CC:	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	device-drivers-devel@...ckfin.uclinux.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH] ASoC: adau1373: adau1373_hw_params: Silence overflow
 warning

On 03/11/2013 04:01 AM, Lars-Peter Clausen wrote:
> On 03/10/2013 06:34 PM, Tim Gardner wrote:
>> ADAU1373_BCLKDIV_SOURCE is defined as BIT(5) which uses UL constants. On
>> amd64 the result of the ones complement operator is then truncated to
>> unsigned int according to the prototype of snd_soc_update_bits(). I think
>> gcc is correctly warning that the upper 32 bits are lost.
>>
>> sound/soc/codecs/adau1373.c: In function 'adau1373_hw_params':
>> sound/soc/codecs/adau1373.c:940:3: warning: large integer implicitly truncated to unsigned type [-Woverflow]
>>
>> gcc version 4.6.3
>>
>> Cc: Lars-Peter Clausen <lars@...afoo.de>
>> Cc: Liam Girdwood <lgirdwood@...il.com>
>> Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
>> Cc: Jaroslav Kysela <perex@...ex.cz>
>> Cc: Takashi Iwai <tiwai@...e.de>
>> Cc: device-drivers-devel@...ckfin.uclinux.org
>> Cc: alsa-devel@...a-project.org
>> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
>> ---
>>  sound/soc/codecs/adau1373.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/sound/soc/codecs/adau1373.c b/sound/soc/codecs/adau1373.c
>> index 068b3ae..56ed788 100644
>> --- a/sound/soc/codecs/adau1373.c
>> +++ b/sound/soc/codecs/adau1373.c
>> @@ -132,7 +132,7 @@ struct adau1373 {
>>  #define ADAU1373_DAI_FORMAT_I2S		0x2
>>  #define ADAU1373_DAI_FORMAT_DSP		0x3
>>  
>> -#define ADAU1373_BCLKDIV_SOURCE		BIT(5)
>> +#define ADAU1373_BCLKDIV_SOURCE		(unsigned int)BIT(5)
> 
> Hm, that's a bit ugly. How about the following instead:
> 
> diff --git a/sound/soc/codecs/adau1373.c b/sound/soc/codecs/adau1373.c
> index 068b3ae..1aa10dd 100644
> --- a/sound/soc/codecs/adau1373.c
> +++ b/sound/soc/codecs/adau1373.c
> @@ -133,6 +133,8 @@ struct adau1373 {
>  #define ADAU1373_DAI_FORMAT_DSP		0x3
> 
>  #define ADAU1373_BCLKDIV_SOURCE		BIT(5)
> +#define ADAU1373_BCLKDIV_SR_MASK	(0x07 << 2)
> +#define ADAU1373_BCLKDIV_BCLK_MASK	0x03
>  #define ADAU1373_BCLKDIV_32		0x03
>  #define ADAU1373_BCLKDIV_64		0x02
>  #define ADAU1373_BCLKDIV_128		0x01
> @@ -937,7 +939,8 @@ static int adau1373_hw_params(struct snd_pcm_substream
> *substream,
>  	adau1373_dai->enable_src = (div != 0);
> 
>  	snd_soc_update_bits(codec, ADAU1373_BCLKDIV(dai->id),
> -		~ADAU1373_BCLKDIV_SOURCE, (div << 2) | ADAU1373_BCLKDIV_64);
> +		ADAU1373_BCLKDIV_SR_MASK | ADAU1373_BCLKDIV_BCLK_MASK,
> +		(div << 2) | ADAU1373_BCLKDIV_64);
> 
>  	switch (params_format(params)) {
>  	case SNDRV_PCM_FORMAT_S16_LE:
> 
> 

That seems way more complicated then need be. It also uses 2 bits in the
mask whereas the original code only used 1, e.g., bit 5. Is that correct ?

How about just open coding the macro thusly:

#define ADAU1373_BCLKDIV_SOURCE (1<<5) /*BIT(5)*/

rtg
-- 
Tim Gardner tim.gardner@...onical.com
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