> On 2 Oct 2024, at 23:53, Christos Margiolis <[email protected]> wrote:
>
> Alban Hertroys wrote:
>> Meanwhile, several people here suggested that devd is the way to go
>> about this. I had actually looked into that a bit, but that seemed to
>> require a related device node in /dev, and there’s neither one for pcm
>> nor for uaudio, so I discarded that as not being a viable option.
>> Perhaps too soon.
>
> Audio device nodes are /dev/dspX, where X is the unit number, which has
> a 1-1 relation with the pcmX unit number, so pcm2's device node is
> /dev/dsp2.
Doh! I knew that, just didn’t realise it while writing that devd config.
I got it working now. Here’s what I came up with:
> cat /usr/local/etc/devd/uaudio.conf
notify 100 {
match "system" "USB";
match "subsystem" "DEVICE";
match "type" "ATTACH";
match "vendor" "0x152a";
match "product" "0x8750";
action "/usr/bin/touch /var/run/usb.0x152a.0x8750";
};
notify 100 {
match "system" "USB";
match "subsystem" "DEVICE";
match "type" "DETACH";
match "vendor" "0x152a";
match "product" "0x8750";
action "/bin/rm -f /var/run/usb.0x152a.0x8750";
};
notify 100 {
match "system" "DEVFS";
match "subsystem" "CDEV";
match "type" "CREATE";
match "cdev" "dsp[0-9]";
action "test -f /var/run/usb.0x152a.0x8750 && \
PCM=`echo $cdev | sed 's@^dsp@@'` && \
sysctl hw.snd.default_unit=${PCM} \
dev.pcm.${PCM}.play.vchans=0 \
dev.pcm.${PCM}.bitperfect=1";
};
As you can see, I build in a check that it’s the correct device before starting
to set sysctl’s, by checking against a file created in /var/run. I’m not too
enthusiastic about that solution… Better suggestions are welcome.
It would be nice if I could set a variable in the USB ATTACH and ‘match’ that
in the CDEV CREATE step to filter the rule, or something like that.
Originally I tried checking for the device using:
test "`sysctl -n dev.pcm.${PCM}.%desc`" = 'Topping D90SE’
, but that statement seems to require the double-quotes for test to accept it,
which conflict with the double-quotes of the action string. I couldn’t find a
way to escape those inner quotes. So that’s another issue I ran into, although
approaches to use the USB attach event for matching the dsp device to the usb
device are clearly superior to reading out a sysctl that’s an effect of it.
Additionally, I noticed that other people also use sed or similar to cut the
device number off the cdev variable in their devd configs. That would have been
a convenient variable to have available by default, I think.
I mean, obviously it’s cool that we can show off how good we are at looking up
sed expressions on Google, but as a data engineer I can’t help but feel that
the data that we need for these configs could be easier to get at.
All in all, I got it working, thanks to the help here.
Regards,
Alban Hertroys
--
There is always an exception to always.
