Re: [LAU] RTC/HPET timer permissions

On 11/26/2012 03:03 PM, Clemens Ladisch wrote:
> Jeremy Jongepier wrote:
>> On 11/25/2012 01:23 PM, Clemens Ladisch wrote:
>>> Using the RTC or HPET devices directly is necessary only if
>>> the kernel does not use them for timers. Nowadays, kernels do, and
>>> applications use the proper timer APIs.
>>
>> What are those timer API's?
>
> POSIX timers, interval timers, nanosleep(), usleep(), poll() timeout.
>

Thanks. Having played around with cyclictest I have a slight notion of
what this all means ;)

>>> You'd need this only if you're using some audio application that hasn't
>>> been updated for many years.
>>
>> So this section has become deprecated?
>> http://wiki.linuxmusicians.com/doku.php?id=system_configuration#hardware_timers
>
> Only if all applications actually have been updated.
> Wasn't there some sequencer (Rosegarden? Muse?) that still uses RTC?
>

No idea. But I think I'm going to modify that section anyway because
apparently setting permissions on /dev/rtc and/or /dev/hpet is not
necessary anymore (in general).

>> And how does the snd-hrtimer module relate to this matter?
>
> It's for some timers used internally by ALSA, and loaded automatically.
>

In what kind of situations would it load automatically? Because it never
does on my machines, I have to either load it myself or add it to
/etc/modules
Software like Qtractor can use it too when the module is loaded. Is this
recommended? Does it improve MIDI timing for instance? How does it
compare to the default timer setting?

Regards,

Jeremy

>
> Regards,
> Clemens
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Received on Tue Nov 27 16:15:01 2012