RPi4 dual screen with touchscreen

[DarkPaladin]

Pi Model: 4B 8GB
Power Supply: Canakit
RetroPie Version: 4.7.1 (Buster)
USB Devices connected: Waveshare 7" touchscreen, Xinmo Arcade controller, Dell KB
Controller used:. Xinmo 2-Player Arcade
Error messages received: SDL / EGL load failure
HDMI0: Waveshare 7" touchscreen
HDMI1: Dell 1905FP

I have looked through here and Google and could not find a matching issue.

I am installing the hardware in a full size cabinet that I've gutted. I am trying to make it so that I can play on the 1905 screen, while leaving the touchscreen on the ES menu to scroll through the library (Dell monitor will be in cabinet, rotated 90 degrees; touchscreen will be mounted externally and player accessible). Based on everything I'm reading this feature does not exist yet.

The immediate issue I have is with the FKMS driver. The Waveshare touchscreen requires me to disable the FKMS driver and use its own configuration, especially since I want to rotate 90 degrees. But if I disable the FKMS driver, RetroPie runs into the SDL/EGL error and will not load the GUI.

Waveshare config (per manufacturer):
max_usb_current=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0
hdmi_force_hotplug=1
hdmi_drive=1
display_rotate=1

Is there a different driver I should try loading, or do I need to submit a feature request and wait?

[mitu]

@darkpaladin said in RPi4 dual screen with touchscreen:

The immediate issue I have is with the FKMS driver. The Waveshare touchscreen requires me to disable the FKMS driver and use its own configuration, especially since I want to rotate 90 degrees. But if I disable the FKMS driver, RetroPie runs into the SDL/EGL error and will not load the GUI.

On the PI4, disabling the (f)kms overlay/driver will result in an unsupported configuration, with any GPU drivers disabled. You won't be able to use RetroPie with it.

Is there a different driver I should try loading, or do I need to submit a feature request and wait?

No, there isn't. Not sure why the Waveshare screen needs the standard Pi4 GPU drivers disabled - maybe because of rotation support ? In any case, using both screens will require X11/X.org running, at which point you may be able to rotate the display/screens using xrandr/arandr. It's not a supported configuration for RetroPie, but it may help you using both screens at the same tie.