Never judge a boot by the screen

scope: generic · severity: law · confidence: proven · subsystem: boot

Mainline does not light the panel until display bring-up lands, which is typically late. Until then a fully booted device and a hung one look identical: dark, or holding whatever frame the bootloader last painted — a vendor logo, a charging icon.

Judge a boot by a channel that exists before the display does:

ip addr                 # did the USB gadget come up on the host?
fastboot devices        # a line here means the bootloader, not your kernel
cat /proc/version       # which build actually answered

Set PORTHOLE_PANEL_STAYS_DARK=1 in the profile while this is true, so tools and future readers know the screen carries no information.

The inverse trap is worse: a device that does paint something can be showing you the bootloader’s last frame from a kernel that panicked seconds ago.