hdmi-boot-delay

#!/usr/bin/env python3

import os, sys, re, time, signal, subprocess as sp


tvs = '/opt/vc/bin/tvservice'


def get_hdmi_res():
	# state 0x120006 [DVI DMT (82) RGB full 16:9], 1920x1080 @ 60.00Hz, progressive
	# state 0x40001 [NTSC 4:3], 720x480 @ 60.00Hz, interlaced
	proc = sp.run([tvs, '-s'], check=True, stdout=sp.PIPE)
	mode = proc.stdout.decode().strip()
	print(f'Display mode: {mode}')
	m = re.search(
		r'^state (?P0x[\da-fA-F]+) \[(?P[^\]]+)\].*?'
		r'\s+(?P\d+)x(?P\d+)\s+@\s+(?P[\d.]+)Hz\b', mode )
	if not m: return
	if 'NTSC' in m.group('m'): return
	return int(m.group('w')), int(m.group('h'))


def main():
	import argparse
	parser = argparse.ArgumentParser(
	description='Script to wait until HDMI display is plugged-in and configured.')
	opts = parser.parse_args(sys.argv[1:])

	signal.signal(signal.SIGINT, lambda *s: sys.exit())
	try:
		ev, mon = None, sp.Popen( [tvs, '-M'],
			stdout=sp.PIPE, stderr=sp.STDOUT )
		while True:
			res = get_hdmi_res()
			if res:
				if ev is None: return # everything already setup
				break
			ev = mon.stdout.readline().decode().strip()
			print(f'Display event: {ev}')
			time.sleep(0.5) # trivial debounce
			if 'HDMI is attached' in ev:
				sp.run([tvs, '--preferred'])
				time.sleep(0.5) # to let display catch-up, if necessary
			# elif 'HDMI cable is unplugged' in ev: sp.run([tvs, '--off'])
	finally:
		mon.terminate()
		try: mon.wait(2)
		except sp.TimeoutExpired: mon.kill()

	w, h = res
	time.sleep(1) # just in case
	print(f'Resizing framebuffer to {w}x{h}')
	sp.run(f'fbset -xres {w} -yres {h}'.split(), check=True)
	mode = sp.run(['fbset'], stdout=sp.PIPE, check=True)
	print(mode.stdout.decode().strip())


if __name__ == '__main__': sys.exit(main())

hdmi-boot-delay.service

[Unit]
DefaultDependencies=no
Requires=local-fs.target
After=local-fs.target

[Service]
Type=oneshot
ExecStart=hdmi-boot-delay