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raspberrypi / utils

A collection of scripts and simple applications
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RaspberryPi 4 - ArchlinuxARM: Can't open device file: /dev/vcio #52

Closed danieletorelli closed 8 months ago

danieletorelli commented 8 months ago

Hello, I'm experiencing this issue on my RaspberryPi 4 since Archlinux ARM started using those binaries some day ago as /dev/vcio doesn't seem to be created anymore.

Kernel:

Linux alarm 6.2.10-1-aarch64-ARCH #1 SMP PREEMPT_DYNAMIC Fri Apr  7 10:32:52 MDT 2023 aarch64 GNU/Linux

Steps to reproduce:

~ # vcgencmd 
Can't open device file: /dev/vcio
Try creating a device file with: sudo mknod /dev/vcio c 100 0

Maybe someone here can help me to figure this out. Thank you!

cc: @graysky2

graysky2 commented 8 months ago

I suspect your issue is that you're running the vanilla linux kernel (linux-aarch64) and not the RPi Foundation based kernel (linux-rpi).

danieletorelli commented 8 months ago

Your suspect is right.

Before it was all working well with the vanilla kernel thanks probably to raspberrypi-firmware package, that has been deprecated 3 days ago in favor of raspberrypi-utils from this repo.

Switching for linux-rpi kernel fixed this issue.

graysky2 commented 8 months ago

Honestly don't know about vanilla kernel. If you want cool stuff on the RPi platform like hw decoding, use linux-rpi.

pathcheatsheet commented 8 months ago

Hello,

Looks like I am having a very similar issue. I am trying to get a set of python scripts (pipresents) running on a RPi 4B. I do not know Python but the code seems to execute vcgencmd and throws an error. When I run vcgencmd as non-root, it throws OP's error. (Tried this on Arch ARM aarch64 as well as armv7h; both running linux-rpi; however it does work on RPi OS but I don't want to use a Debian-based system.) It looks like there is a permission problem as it does what it has to as root:

[szg@alarm ~]$ uname -a
Linux alarm 6.1.61-2-rpi-ARCH #1 SMP PREEMPT Mon Nov  6 08:36:16 MST 2023 aarch64 GNU/Linux
[szg@alarm ~]$ vcgencmd get_mem gpu
Can't open device file: /dev/vcio
Try creating a device file with: sudo mknod /dev/vcio c 100 0
[szg@alarm ~]$ sudo vcgencmd get_mem gpu
gpu=76M

Exactly the same on armv7h. Not sure whether this is expected behaviour since vcgencmd does work under normal user on RPi OS Bullseye:

szg@raspberrypi:~ $ uname -a
Linux raspberrypi 6.1.21-v8+ #1642 SMP PREEMPT Mon Apr  3 17:24:16 BST 2023 aarch64 GNU/Linux
szg@raspberrypi:~ $ vcgencmd get_mem gpu
gpu=76M
pathcheatsheet commented 8 months ago

A quick update: booted back into Arch armv7 and added the szg user to the video group there. This does not help, even though permissions for /dev/vcio are identical in both OSes:

crw-rw---- 1 root video 10, 125 Nov  6 18:27 /dev/vcio
danieletorelli commented 8 months ago

@pathcheatsheet In my case it was enough to add my user to the video group, disconnect and reconnect from ssh. I was able to run this after reconnecting:

alarm ~ $ vcgencmd get_mem gpu
gpu=256M

loki ~ $ id
uid=1000(alarm) gid=984(users) groups=984(users),985(video),998(wheel)