[alsa-devel] Miscellaneous ioplug questions

[Takashi Iwai]

On Thu, 09 Aug 2018 20:45:51 +0200,
Rob Duncan wrote:
> 
> I have some questions about some ioplug implementation details:
> 
> - Is the value returned from the pointer callback supposed to be a
>   monotonically increasing value, or should it wrap at the buffer size?
>   The documentation says "get the current DMA position" which isn't
>   clear to me.
> 
> - Must the pointer callback return values that are an integral multiple
>   of the period size, or can it report partial periods?

The ioplug basically emulates the hardware driver behavior, and
basically the pointer callback may return any position.
Hence the answers to the questions above are: yes, it may wrap buffer
size and yes, it may report partial periods.

> - Should the poll FD be made writeable as soon as data is available, or
>   only when at least avail_min is available?

The latter.  Again, ioplug emulates the hardware driver, so the poll
should behave same as the hardware driver does.
(Though, admittedly, not all plugin implementations follow this
strictly....)


Takashi