On 2018-07-29 18:52:36 (-0400), bill-auger wrote: > can you explain why a new group was needed? why remove functionality > from the audio group - that is the commonly expected purpose of the > audio group on every distro i have used that caters to A/V use-cases - > conversely, what purpose would the audio group now serve? The audio group is installed via syusers.d with the systemd package (defined in /usr/lib/sysusers.d/basic.conf). It's one of the system's default groups, which grants access to /dev/audio and /dev/snd/* [1] (/dev/rtc0, mentioned last, got dropped in by jack/jack2 a few years back). The accompanying udev rule can be found in /usr/lib/udev/rules.d/50-udev-default.rules (also part of the systemd package). Traditionally, other software installing own rules, relies on this group and its settings (e.g. libffado, as found in /usr/lib/udev/rules.d/60-ffado.rules). The compromise introduced a long time ago for the jack and jack2 packages (as described upstream on the realtime topic [2]) also relies on the audio group. However, acquiring realtime privileges and accessing audio hardware are two separate things. Note, that while acquiring realtime privileges can be benificial for pro-audio applications, it is not the only use-case! To make things more clear: audio - access specific audio hardware realtime - acquire realtime privileges (which you can use for pro-audio) > most such distros (including the arch derivative i use) also have a > package which is usually named similarly to 'proaudio-settings', that > depends on JACK and the kernel-rt and provides optimizations for > real-time audio use - but the JACK package should not require the > kernel-rt nor any privileges or optimizations; simply because JACK > itself does not require those and is intended to be fully usable > without them That's exactly why the realtime group will exist and realtime-privileges will become an optional dependency for jack and jack2. It doesn't make any sense to have realtime-privileges depend on linux-rt and or jack/jack2, as realtime-privileges is meant to extend the capabilities of what a certain user group is allowed to achieve with the system (and the system's hardware) and therefore is an extension of what said group can achieve with linux-rt and/or jack/jack2. > i proposed before the idea of maintaining a consistent > 'proaudio-settings' optimizations package in the arch upstream - does > this 'realtime-privilege' package do nothing more than create > 'realtime' group, with no other optimizations? - if it also has other > general optimizations for real-time audio, then i suggest it be > renamed to a commonly recognizable name like: 'proaudio-settings' - if > not, then i still propose such a 'proaudio-settings' optimization > package - such a package would necessarily depend on JACK and the > 'realtime-privilege' package - but that would make it clear that it is > the optimization package that provides realtime privileges and not the > JACK package The "optimizations" (which are more capabilities given to the realtime group) are now all in the realtime-privileges package, instead of redundantly packaged in jack/jack2 and being bound to the audio group (which is there for accessing audio hardware, not for acquiring realtime privileges). Again: Acquiring realtime is not a pro-audio only thing. jack/jack2 can work without acquiring realtime (mind [2]). However, one can extend reliability of some software by acquiring realtime privileges. Therefore it makes no sense to have separate settings for pro-audio, as realtime-privileges is a more general approach to whatever one wants to achieve with that. In other words: You wouldn't want to have to install jack/jack2 just to acquire realtime privileges for another piece of software, that is non pro-audio related, but you can now optionally extend jack/jack2's capabilities by using realtime-privileges (with a more clear distinction as to what the groups you're in actually stand for). I hope this answers your questions. Best, David [1] https://wiki.archlinux.org/index.php/Users_and_groups#Pre-systemd_groups [2] http://jackaudio.github.io/faq/linux_rt_config.html -- https://sleepmap.de
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