[pulseaudio-discuss] system-wide daemon

Colin Guthrie gmane at colin.guthr.ie
Tue Feb 9 11:31:54 PST 2010

'Twas brillig, and Markus Rechberger at 09/02/10 19:07 did gyre and gimble:
>>> How about a FM USB Transceiver which uses UAC (USB Audio Class)
>>> Why the heck should only the person sitting infront of it be allowed to use it
>>> The person sitting infront of it could listen to audio while another
>>> one could transmit audio (I do have such an engineering sample here).
>> So you transmit something in the clear and you are suprised that someone
>> "hijacks" your data? Again the relevance to this discussion is lost on
>> me I'm afraid.
> the user sitting infront of it could listen to FM radio, while another
> one is using the FM Transmit (line-out)
> unit.
> In your scenario such devices do not exist and are prohibited.

If this is how the device is designed to be used, then it should present
itself as two separate devices to the kernel and appropriate ACLs could
be placed on each to allow different users to access it simultaneously.

>>> I see your 'designed' way just as a valid usecase as my one (which
>>> basically was requested multiple times by multiple
>>> people already).
>> Personally I don't. The active user has control of the sound hardware.
>> If the machine is "inactive" then a pseudo session can be registered
>> (i.e. in the case of gdm login). If the active user (be it a real user
>> or "gdm") decides he wants the audio from the lower level system then
>> they should configure their system to recieve the audio via some kind of
>> controlled IPC mechinism and play it back accordingly.
>> Bypassing this layer and accessing things directly is not IMO a good
>> design. Everything is possible with the appropriate mechanisms in place
>> and no functionality is sacrificed, but you have to be prepared to
>> accept that old approaches will not last forever nor survive the tests
>> of time.
> your scenario is definitely over engineered for many people out there.

I wouldn't call this overdesign. Quite the opposite. Yes to get this
rather bizarre scenario working it would be complex, but to make it work
out of the box in this way in PA itself is far from simple. I've already
listed the 5 relevant points that would need addressing for this to work
and there are significant design hurdles to overcome there. That is what
I would consider overdesign - doing something very complex to support a
pretty niche use case.



Colin Guthrie

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