Kernel 4.4.31-bone-rt-r14 sgx-startup.sh - not setting permissions

[Moscowbob]

I have just built fresh kernel, dtb, u-boot and sgx as per RCN eewiki and I have also built Qt 5.6.2.

Everything is working correctly except for one problem which I do not understand and hope somebody could explain.

After installing sgx drivers and a reboot I have everything as per instructions:

lsmod | grep omaplfb

omaplfb                12356  0 

tilcdc                 26717  1 omaplfb

pvrsrvkm              157212  1 omaplfb

but my Qt Quick programs only work when run as root (sudo).

Looking at the sgx-startup script, /dev/pvrsvrkm should be set with 666 permissions, but after startup this is what I get:

ls -al /dev/pvrsrvkm 

crw------- 1 root root 247, 0 Nov 27 20:54 /dev/pvrsrvkm

When I run:

sudo /etc/init.d/sgx-startup.sh stop

sudo /etc/init.d/sgx-startup.sh start

I get:

sgx: Starting PVR

/usr/local/bin/pvrsrvctl: SrvInit failed (already initialized?) (err=129)

 

ls -al /dev/pvrsrvkm 

crw-rw-rw- 1 root root 247, 0 Nov 27 21:48 /dev/pvrsrvkm

Permissions are now correct for running program as normal user.

my programs run correctly with platform eglfs - which is what I want.

My questions:

1. Why does sgx-startup.sh not set the permissions correctly on boot and is there a way to solve this?

Thanks in advance

Rob

[Robert Nelson]

Oh let's patch that in the sgx-startup.sh script.. Probably after the
modprobe/pvrsrvct start..

Send me a patch and i'll push it out...

Regards,

--
Robert Nelson
https://rcn-ee.com/

[Moscowbob]

Thank you Robert but I am  not sure what you mean, would you kindly clarify.

As far as I understand the script, you are setting the permissions to 666 and you also start the service.

What I do not understand is how and why the permissions are not set when the script runs in the first place.

Rob

[Moscowbob]

This is confusing me even more now - I added a "stat" on /dev/pvrsrvkm in the sgx-startup.sh, at the end before the "start" finishes and the permissions areset correctly -

debian@arm:~$ systemctl status sgx-startup

● sgx-startup.service - LSB: Start daemon at boot time

   Loaded: loaded (/etc/init.d/sgx-startup.sh; generated; vendor preset: enabled

   Active: active (exited) since Mon 2016-11-28 07:37:30 UTC; 1min 59s ago

     Docs: man:systemd-sysv-generator(8)

   CGroup: /system.slice/sgx-startup.service

Nov 28 07:37:27 arm systemd[1]: Starting LSB: Start daemon at boot time...

Nov 28 07:37:27 arm sgx-startup.sh[363]: sgx: Starting PVR

Nov 28 07:37:30 arm systemd[1]: Started LSB: Start daemon at boot time.

Nov 28 07:37:30 arm sgx-startup.sh[363]: 666  <<<<< just before the script completes

debian@arm:~$ ls -al /dev/pvrsrvkm 

crw------- 1 root root 247, 0 Nov 28 07:37 /dev/pvrsrvkm

but still the permissions are 600 as can be seen above.

Any advice will be greatly appreciated.

Thanks

Rob

[Moscowbob]

After hours of reading all sorts and my brain blowing up, I think I might have found the reason for the problem. However, as a Linux noob, I am now stuck and hope one of our gurus will shed light on this.

This is where I am now:

1. Copied the "start" section of sgx-startup.sh to a new file and started fiddling.

2. Found that there appears to be some delay between modprobe pvrsrvkm , deleting the /dev/pvrsrvkm file and what I assume is the kernel module setting permissions on the file.

3. When I moved the delete and mknod to after the /usr/local/bin/pvrsrvctl --start --no-module and added a sleep 1, the file permissions were set correctly.

Unfortunately this only work when I run the script manually, it doe not work with reboot (maybe sleep cannot be used)

So, I am still trying to find a solution, but I am running out of things to try 

Thanks

Rob

[Moscowbob]

After spending some time with systemd and udec documentation and playing with udevadm I managed to find a solution.

No need to modify the sgx-startup.sh script, I just added a permission a sgx-permissions.rule to /etc/udev/rules.d with the folowing line - SUBSYSTEM=="pvr", GROUP="video", MODE="0660".

I am not sure, maybe somebody can clarify - I think the chmod 666 /dev/pvrsrvkm has no effect since when modprobe is called, kernel and udev events will trigger and the default permissions for udev on devices is 600.

Regards

Rob