[alsa-devel] 'BATCH flag for USB' and 'ALSA Core Challenges'

[Takashi Sakamoto]

Hi,

(If I were in ±0200、I would have joined in the meeting...)

There're some interesting issues in the minutes. Would I request someone
more explaination about it?

> BATCH flag for USB: Arun.
> =========================
>  - Flag does not respond to reality, lets deprecate it. no users.
>  - Dylan: need to know transfer size for CRAS (uses extra samples for
> buffering). 
>  - BATCH flag means period size transfers, applications that use new
> granularity API can ignore batch flag. Pierre: to implement.

The first item said 'BATCH flag should be deprecated', while
BLOCK_TRANSFER flag is not mentioned. Are there some discussions about
the differences between these two flags?

I think the APIs suppose that the number of PCM frames in one
transferring is the same as the number of PCM frames in one period of
buffer. PCM device driver developers must always satisfy this principle?
Or the APIs allow them to implement such differences and present proper
value to userspace?

> ALSA Core Challenges:
> ======================
> - ALSA Core locking is complicated. Core code is quite difficult to
> understand.
> - PCM linking makes things complex
> - Add documentation for locks. 
>  - Controls can be hidden in UI tools through iface_cards.
>  - DPCM hidden PCMs should not be shown in usermode, hide them from
> Usermode

The third item mentions about 'iface_cards', while there'no such
structure in kernel/userspace.
What's it and what is the 'UI tools'? Does it means to produce some GUI
widget?

Sorry just to take my questions but I'm not a participant of the meeting...


Regards

Takashi Sakamoto