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SubjectRe: [PATCH] ASoC: adau1373: adau1373_hw_params: Silence overflow warning
On 03/11/2013 04:37 PM, Tim Gardner wrote:
> 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@metafoo.de>
>>> Cc: Liam Girdwood <lgirdwood@gmail.com>
>>> Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
>>> Cc: Jaroslav Kysela <perex@perex.cz>
>>> Cc: Takashi Iwai <tiwai@suse.de>
>>> Cc: device-drivers-devel@blackfin.uclinux.org
>>> Cc: alsa-devel@alsa-project.org
>>> Signed-off-by: Tim Gardner <tim.gardner@canonical.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 ?

The BCLKDIV has three fields. The bitclock divider (bit 0-1), the samplerate
(bit 2-4) and the source select (bit 5). Here we want to update the bitclock
divider field and the samplerate field. When I wrote the code I was lazy and
used ~ADAU1373_BCLKDIV_SOURCE as the mask, which for this register is
functional equivalent to ADAU1373_BCLKDIV_SR_MASK | ADAU1373_BCLKDIV_BCLK_MASK.

>
> How about just open coding the macro thusly:
>
> #define ADAU1373_BCLKDIV_SOURCE (1<<5) /*BIT(5)*/

But now there is a inconsistency where we sometimes use (1<<x) and sometimes
BIT(x). I prefer my solution.

- Lars


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