[pulseaudio-discuss] [PATCH v8] pipe-source: implement autosuspend option

[Georg Chini]

On 21.02.2018 21:02, Georg Chini wrote:
> On 21.02.2018 20:15, Raman Shishniou wrote:
>> On 02/21/2018 09:41 PM, Raman Shuishniou wrote:
>>> 21.02.2018 20:07, Georg Chini пишет:
>>>> Maybe you misunderstood me. What I mean, is that the pipe can be
>>>> opened for writing as long as we are suspended. So it open when
>>>> we see that the source is suspended or when we auto suspend. Close
>>>> it as soon as the source gets unsuspended. This will avoid POLLHUP
>>>> during suspend completely. While auto suspended, we additionally have
>>>> to listen for POLLIN.
>>>> This way we can only get POLLHUP (or POLLIN with no data) when the
>>>> source is running.
>>>>
>>> I think I understand. We need to keep our writer opened while 
>>> transition
>>> from autosuspended to opened state and just set events = 0.
>
> Exactly. I was also thinking about how to decide if data can be discarded
> or needs to be posted. On resume, the SET_STATE handler could set a
> just_unsuspended flag and when we know auto suspend is the only
> suspend cause, we can additionally set a resume_from_auto_suspend
> flag when we send the unsuspend message. In the thread function we
> could then check if
>
> just_unsuspended && resume_from_autosuspend -> post pending data, 
> reset flags
> just_unsuspended && !resume_from_auto_suspend -> discard data, reset 
> flags
> !just_unsuspended -> post data
>
> But that's only an idea.
It's even simpler, because the old and new suspend cause are available 
in the
SET_STATE handler (or in the set_state_in_io_thread() callback). So 
there we can
do:
if (old_cause == AUTO_SUSPEND && new_cause == 0) -> 
resume_from_auto_suspend = true
else if (old_caue != 0 && new_cause == 0) -> resume_from_user_suspend = true

BTW, maybe we should have a new suspend cause for that. Currently,
the best suspend cause we could use is PA_SUSPEND_UNAVAILABLE.
In the future however, it is planned, that streams get rescued when
the suspend cause is PA_SUSPEND_UNAVAILABLE and I guess that is
not what you want in your case.