Re: Use less number of BDs in i810

[Takashi Iwai <tiwai@suse.de>]

At Wed, 07 Aug 2002 12:54:23 +0530,
Shaju Abraham wrote:
> 
> Hi all,
>          I suppose that present implementation of i810 driver uses
> 32 BDs.

no, it's maximal 32 BDs.
and, in the current code, a period (as the alsa's terminology)
corresponds to a BD, i.e. maximal 32 periods.

> Can u pls direct me how to reduce this number to say only 16 or 8 BDs.
> 
> Also, now if the number of frags I am getting is 8, size of each frag I am
> getting is 4456 bytes.  I have two questions regarding this.
> 
> 1.         How can I force the fragment size to be  abt 1k or 2k bytes?

via alsa-lib API.  set the period size (or period time) explicitly.

> 2.         Is it strange that this number is not a multiple of 512 bytes?  ( I
> am getting physize of 35648 bytes.  not 32K ? )

in the current code it's ok.  the size of each BD is arbitrary.

but if we use discontinuous kernel pages via scatter-gather mechanism,
the period size must be aligned to the power of two.  this is not
implemented on intel8x0 driver yet, but once if it's there, the size 
will be restricted.


Takashi


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