Hey for testing purposes I try to recreate/reverse engineer the way the bcmd is dealing with the GPIOs, etc to power up/down nodes and to put them into MSD mode. If bmcd is stoppped and I do on a TP2.5 board:

gpioset -c 2 node$NODE-rpiboot=1 & BG_PIDS="$BG_PIDS $!"
# TP2.5
# NODE1_OUTPUT_SWITCH_V2_5 = c0.192
# NODE1_SOURCE_SWITCH_V2_5 = c0.193
# USB_SWITCH_V2_5 = c0.194
gpioset -c 0 192=0 193=0 194=1 & BG_PIDS="$BG_PIDS $!"
sleep 1
echo enabled > /sys/bus/platform/devices/node$NODE-power/state

I see some secs later the MaskRom device popping up allowing me to use

rkdeveloptool db $RK3588_SPL_LOADER

and I get the RK1 devices into MSD mode. If I do this with a CM4 I expect Vendor 0x0a5c Product 0x2711) to pop up as usb device. So I can use rpiboot. But unfortunatly the USB device for the CM4 MSD is not appearing, so I can't use rpiboot. Does some one have ideas, what I am missing? (The idea is to experiment with storage mode gadged on CM4/CM5s.)