[alsa-devel] [PATCH] [RFC 8/13] Intel SST sound card driver

[Harsha, Priya]

>-----Original Message-----
>From: Takashi Iwai [mailto:tiwai at suse.de]
>Sent: Tuesday, July 07, 2009 12:56 PM
>To: Harsha, Priya
>Cc: Koul, Vinod; alsa-devel at alsa-project.org
>Subject: Re: [alsa-devel] [PATCH] [RFC 8/13] Intel SST sound card driver
>
>At Tue, 7 Jul 2009 12:46:38 +0530,
>Harsha, Priya wrote:
>>
>> >> >> >
>> >> >> >> +	.access 	=	SNDRV_CTL_ELEM_ACCESS_READWRITE,
>> >> >> >> +	.info 		=	snd_intelmad_line_volume_info,
>> >> >> >> +	.get 		=	snd_intelmad_volume_get,
>> >> >> >> +	.put		=	snd_intelmad_volume_set,
>> >> >> >
>> >> >> >Can it have the dB information via TLV?
>> >> >> No. It actually differs across the 3 sound cards supported and it's
>> >> >> not a direct TLV that can be used.
>> >> >
>> >> >Then you'd set a static TLV entry after creating the ctl element
>> >> >instance, or return a TLV entry dynamically via the tlv callback.
>> >> Sorry I misunderstood. The value that is passed in min and max is in
>> >> dB.
>> >> For min and max values, it's a static dB value that I return. But
>> >> when the volume adjustments need to be done, based on the value
>> >> given by ALSA, I set the sound card registers to reflect that dB
>> >> value.
>> >
>> >The value to be set is always raw.  That is, alsa-lib computes the
>> >raw value from the given dB value based on the TLV information (dB
>> >min/max), supposing the volume scale is logarithmic.
>> >
>> >Isn't it the case for you?
>> Yes. I set the raw min and max values in db. And alsa-lib computes
>> the volume value to be set (which is in between the min and max) and
>> provides the same to the driver. The driver sets the corresponding
>> sound card registers to reflect the same. In our case, the scale is
>> not logarithmic in couple of sound cards and the vendor abstraction
>> file would need to take care of the same to set the registers
>> correctly.
>
>Then it can't be exported as the existing TLV.  The currently defined
>TLV types are logarithmic, linear, and combinations.
>I think it's better to fix the driver side to be logarithmic.
Ok. I will work on it.

Thanks,
Harsha