[alsa-devel] safe support for rewind in ALSA

[Kai Vehmanen]

Hi,

On Thu, 11 Feb 2010, Jaroslav Kysela wrote:

>> However, PA ignores the sound card's interrupts and is woken up by its
>> own timer.
>
> PA can drive the wake-ups using avail_min sw parameter. If this value is
> high enough, no userspace wake up is called, only interrupt is processed
> and internal ring buffer pointers in the driver are updated.

but that's unfortunately not enough. AFAIK glitch-free aims, among other 
things, to minimize power usage for battery powered devices, and to do 
that, you need to minimize hardware interrupts [1]. And for that, 
avail_min won't help.

[1] this is exactly the same thing that is driving Linux tickless
     development:
     http://www.lesswatts.org/projects/tickless/

PS I do agree that avail_min is a very useful, and often overlooked
    feature, of ALSA. But in this specific case it won't help...