| 19 Oct 2025 |
 dramforever | it seems that udev 258 no longer gives permissions on /dev/snd/timer unless snd-timer is loaded | 19:03:43 |
| dramforever | * it seems that udev in systemd 258 no longer gives permissions on /dev/snd/timer unless snd-timer is loaded | 19:03:53 |
 ElvishJerricco | wut... | 19:08:41 |
| dramforever | which would be a regression in systemd but i'm not sure if i'm playing with it wrong | 19:09:10 |
| ElvishJerricco | yea, this is really weird. udev doesn't seem to consider it to be a device until snd_timer is loaded | 19:10:16 |
| dramforever | wait that could be it, right? if uaccess is only giving it permissions if it's successfully detecting it as a real device | 19:10:57 |
| ElvishJerricco | well, note this weird udev rule https://github.com/systemd/systemd/blob/781d9d0789379d1ea1f2ecefb804d41e9c8b6c38/rules.d/70-uaccess.rules.in#L29-L31 | 19:11:51 |
| dramforever | it's been here forever | 19:12:13 |
| ElvishJerricco | which basically says "if any sound subsystem device shows up, then add uaccess to snd/timer and snd/seq" | 19:12:17 |
| dramforever | and on 257 this wasn't a problem | 19:12:39 |
| ElvishJerricco | right I'm not saying the rule is the problem | 19:12:47 |
| ElvishJerricco | I'm saying I don't understand what has changed here | 19:13:01 |
| dramforever | right but point is it's probably something about the uaccess redesign right | 19:13:08 |
| ElvishJerricco | because even if /dev/snd/timer isn't tracked by udev, it should (I think?) still have that rule apply to it when any other sound device appears | 19:13:30 |
| ElvishJerricco | anyway the fix for the test is probably just to check a different device, since something funky is going on with this one specifically | 19:16:35 |
| ElvishJerricco | but I'm still concerned with what's going on with this device specifically | 19:16:45 |
| dramforever | the device itself is normal, this is a fake "static node" device | 19:18:19 |
| dramforever | when you access it the kernel loads the corresponding kernel module | 19:18:46 |
| dramforever | the not normal part is udev not applying the permission to this placeholder device | 19:19:03 |
| dramforever | * the device itself is normal, this is a fake, really placeholder "static node" device | 19:19:10 |
| dramforever | but if that's the case this is a regression in sd 258, this means users can't trigger the module load anymore | 19:21:54 |
| ElvishJerricco | dramforever: I think I'm going to learn something today :P I have never been clear on what "static device nodes" actually are. | 19:24:03 |
| dramforever | so | 19:24:32 |
| dramforever | you notice how you have /dev/snd/timer but lsmod has no snd-timer, right? | 19:24:45 |
| dramforever | go head -c 0 /dev/snd/timer which opens the device, and closes | 19:24:59 |
| dramforever | * go head -c 0 /dev/snd/timer which opens the device, and closes it | 19:25:01 |
| dramforever | now you magically do have snd-timer loaded | 19:25:10 |
| ElvishJerricco | ok | 19:25:50 |
| ElvishJerricco | so, what, userspace creates fake device nodes, and the major/minor thing tells the kernel what it's supposed to be, and the kernel knows to load the corresponding module when it's accessed? | 19:26:26 |
| dramforever | exactly | 19:26:55 |
