modeset(0): drmSetMaster failed: Permission denied

[YuGiOhJCJ Mailing-List]

Hello,

I have built xorg-server, xauth, and xinit with their dependencies.
When I do startx I get "xf86OpenConsole: Cannot open virtual console 7 (Permission denied)".
So, I change the permissions on /dev/tty7 to 660.
Now, when I do startx I get "modeset(0): drmSetMaster failed: Permission denied".

I read in the web that some people use SUID on /usr/bin/Xorg to solve this problem but I am not sure if it is safe to do that and maybe there is a better way.
Same thing for my permissions on /dev/tty7, I would prefer to not change permissions if possible.
With the Xorg provided by my distro, there is no SUID on /usr/bin/Xorg and only 0620 on /dev/tty7 which is better, and it works fine.
So, I am wondering why it does not work with my own Xorg.

Any idea please?

Thank you.
Best regards.

---

Distro: Slackware64 14.2
Kernel: Linux 4.9.24
Built and installed packages:
-bigreqsproto-1.1.2
-compositeproto-0.4.2
-damageproto-1.2.1
-dri2proto-2.8
-dri3proto-1.0
-fixesproto-5.0
-fontsproto-2.1.3
-glproto-1.4.17
-inputproto-2.3.2
-kbproto-1.0.7
-libdrm-2.4.80
-libepoxy-1.4.1
-libfontenc-1.1.3
-libICE-1.0.9
-libpciaccess-0.13.5
-libpthread-stubs-0.1
-libSM-1.2.2
-libvdpau-1.1.1
-libX11-1.6.5
-libXau-1.0.8
-libxcb-1.12
-libXdamage-1.1.4
-libXext-1.3.3
-libXfixes-5.0.3
-libXfont2-2.0.1
-libxkbfile-1.0.9
-libXmu-1.1.2
-libxshmfence-1.2
-libXt-1.1.5
-mesa-17.0.4
-mesa-demos-8.3.0
-pixman-0.34.0
-presentproto-1.1
-randrproto-1.5.0
-recordproto-1.14.2
-renderproto-0.11.1
-resourceproto-1.2.0
-scrnsaverproto-1.2.2
-videoproto-2.3.3
-xauth-1.0.10
-xcb-proto-1.12
-xcmiscproto-1.2.2
-xextproto-7.3.0
-xf86driproto-2.1.1
-xineramaproto-1.2.1
-xinit-1.3.4
-xorg-server-1.19.3
-xproto-7.0.31
-xtrans-1.3.5