Re: snd_pcm_hw_params_get_period_size() returning 0

[Carlos Munoz <carlos@kenati.com>]

Takashi Iwai wrote:

>At Fri, 31 Mar 2006 18:20:42 -0800,
>Carlos Munoz wrote:
>  
>
>>Lee Revell wrote:
>>
>>    
>>
>>>On Fri, 2006-03-31 at 17:00 -0800, Carlos Munoz wrote:
>>> 
>>>
>>>      
>>>
>>>>Does 
>>>>any one know why
>>>>snd_pcm_hw_params_get_period_size() would be returning 0 ? Is it 
>>>>something the driver did/didn't do ?
>>>>
>>>>   
>>>>
>>>>        
>>>>
>>>Argh, please disregard last message, that's not how the hw_params
>>>callback works :-(
>>>
>>>Lee
>>>
>>> 
>>>
>>>      
>>>
>>Hi Lee,
>>
>>I digged further and this is what I found.
>>
>>snd_pcm_hw_params_get_period_size(...., int *val) does retrieve the 
>>correct period size and updates val with it. However, val does not match 
>>the address passed to it. I mean the caller of 
>>snd_pcm_hw_params_get_period_size(.... 0x41becc) passes the address of 
>>where the period size is to be stored as 0x41becc but 
>>snd_pcm_hw_params_get_period_size() gets 0x7b83c0d8 and that's where it 
>>puts the period size.
>>
>>This is on the Renesas SH7343 processor. alsa-lib is a dynamic library. 
>>Should I expect the variable address be the same ?
>>    
>>
>
>No.  They must be different.  The value is stored to the original
>address only when no error returns.  Unless that, a temporary variable
>is used.  That's why you see two distinct addresses.
>
>
>Takashi
>
>
>  
>
Hi Takashi,

I understand what you are saying. However, this is not the case here. 
The original address is wrong. I print the value of val (not _val) 
passed to snd_pcm_hw_params_get_period_size() and it is wrong. See the code:

#ifndef DOXYGEN
int INTERNAL(snd_pcm_hw_params_get_period_size)(const 
snd_pcm_hw_params_t *params, snd_pcm_uframes_t *val, int *dir)
#else
int snd_pcm_hw_params_get_period_size(const snd_pcm_hw_params_t *params, 
snd_pcm_uframes_t *val, int *dir)
#endif
{
    unsigned int _val;
    printf("alsa-lib:snd_pcm_hw_params_get_period_size() - params=%p 
val=%p dir=%p\n",
           params, val, dir);
    int err = snd_pcm_hw_param_get(params, SND_PCM_HW_PARAM_PERIOD_SIZE, 
&_val, dir);
    if (err >= 0)
        *val = _val;

    return err;
}


This printf shows val has an incorrect value (dir is also incorrect). I 
don't think it's related to the alsa-lib but maybe a problem with our 
build tool chain.

Thanks,


Carlos Munoz


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