[H700] Fix screen rotation and enable independent HDMI/internal settings

[fedekrum]

Summary

Enable independent display rotation for HDMI and internal outputs on Allwinner H700 devices (RG40XX-H, RG35XX-H/Plus, etc.), controllable directly from the EmulationStation System Settings menu without editing config files.

Use case: A user wants their HDMI output rotated 90° for a vertical arcade monitor, while keeping the internal screen at 0° (landscape).

Problem

The EmulationStation UI only writes to the global display.rotate key in knulli.conf. However, the emulationstation-standalone launcher already supports per-output rotation keys (display.rotate.hdmi, display.rotate.internal) — it checks display.rotate.{output} first, then falls back to display.rotate.

The issue is that these per-output keys are never populated because:

1. The ES UI only writes display.rotate (global)
2. currentOutput was empty, so the launcher could never determine the active output

Solution

Bridge the gap at the shell level with a sync_rotation_per_output() function that transparently manages per-output rotation values:

• On output change (HDMI plugged/unplugged): restores display.rotate from the saved value for the newly active output
• On same output (user changed rotation in UI): persists the current display.rotate value to the active output key (display.rotate.hdmi or display.rotate.internal)

This approach requires zero changes to EmulationStation — all logic is contained in the H700 knulli-resolution script.

Changes (minimal, surgical edits)

Change	Type	Original code modified?
LAST_STATE_FILE variable	1 line added	No
sync_rotation_per_output() function	New block inserted	No (between existing functions)
setOutput: call sync function	1 line added	No
currentOutput: return hdmi or internal	Fill empty case	No (was empty)
supportSystemRotation: return exit 1	1 line in empty case	No (was empty)
currentResolution: swap WxH for portrait	Modified 2 lines	Yes — fbset output captured in variable

Only 2 original lines are modified. Everything else is new code or fills previously empty case blocks.

Configuration

Per-output rotation is managed automatically. Users simply change "SCREEN ROTATION" in ES System Settings as usual. The sync function handles the rest:

# These keys are managed automatically — users do NOT need to edit them
display.rotate=1            # Global (what ES UI reads/writes)
display.rotate.hdmi=1       # Saved HDMI rotation
display.rotate.internal=0   # Saved internal rotation

Technical Details

• supportSystemRotation returns exit 1 to force software rotation via --screenrotate. Hardware rotation on the H700 (via fb0/rotate) causes image artifacts on HDMI.
• currentResolution swaps width/height when rotation is 90° or 270° so ES themes render with correct aspect ratio in portrait mode.
• HDMI state tracking uses /var/run/last_hdmi_state (volatile, cleared on reboot).

Testing

Tested on RG40XX-H running Knulli alpha 20260209:

• ✅ HDMI output rotated 90° for vertical arcade setup
• ✅ Internal display unrotated when HDMI disconnected
• ✅ Rotation values persist independently per output
• ✅ HDMI hot-plug switching works correctly
• ✅ Rapid HDMI connect/disconnect does not cause hangs
• ✅ No regression on standard (non-rotated) usage
• ✅ Zero impact on devices without HDMI (sync is a no-op)

[fedekrum]

🛠️ Manual installation (no compilation needed)

For anyone who wants to test this before it gets merged. Tested on RG40XX-H with Knulli alpha 20260209.

# 1. SSH into the device (default password: linux)
ssh root@<DEVICE_IP>

# 2. Remount filesystem as read-write
mount -o remount,rw /

# 3. Back up the original script
cp /usr/bin/knulli-resolution /usr/bin/knulli-resolution.bak

# 4. Download the patched script directly from this PR
curl -sL https://raw.githubusercontent.com/fedekrum/knulli-linux/h700-rotation-support/board/allwinner/h700/fsoverlay/usr/bin/knulli-resolution \
  -o /usr/bin/knulli-resolution

# 5. Ensure it is executable
chmod 755 /usr/bin/knulli-resolution

# 6. Save overlay so the change persists across reboots
knulli-save-overlay

# 7. Reboot
reboot

How to use

Change SCREEN ROTATION in ES System Settings as usual. The sync function handles per-output values automatically:

• While on HDMI → rotation saved to display.rotate.hdmi
• While on internal → rotation saved to display.rotate.internal
• Plug/unplug HDMI → correct rotation restored automatically