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Is hdmi_force_hotplug the same as manually turning on HDMI via tvservice?

Posted: Tue Apr 17, 2018 2:12 pm
by paulslocum
Does hdmi_force_hotplug=1 do anything unique, or is it the effectively same as automatically turning on an HDMI mode using tvservice in rc.local?

Re: Is hdmi_force_hotplug the same as manually turning on HDMI via tvservice?

Posted: Tue Apr 17, 2018 2:27 pm
by DougieLawson
hdmi_force_hotplug forces the GPU to enable the HDMI settings even when there's no HDMI device connected. You'll usually need to include hdmi_group=n & hdmi_mode=nn with some override settings for your HDMI device.

Re: Is hdmi_force_hotplug the same as manually turning on HDMI via tvservice?

Posted: Wed Apr 18, 2018 2:59 pm
by paulslocum
Best I can tell, tvservice does the same thing. What I'm wondering is if there's any difference between the two technically, like does hdmi_force_hotplug set some bits on the HDMI port to improve compatibility, or is it only forcing the HDMI on (the same as turning on an explicit HDMI mode with tvservice)

Re: Is hdmi_force_hotplug the same as manually turning on HDMI via tvservice?

Posted: Wed Apr 18, 2018 3:35 pm
by DougieLawson
The config.txt option is automatic at boot time. Most folks won't ever need it, 99.99% of HDMI display devices "just work" with a Raspberry with nothing special needed in /boot/config.txt or with the tvservice command.

Re: Is hdmi_force_hotplug the same as manually turning on HDMI via tvservice?

Posted: Wed Apr 18, 2018 9:00 pm
by paulslocum
I hope so, but I find quite a few reports of the issue on the forums, and I didn't have to test many devices to find one that didn't work, so I think the issue may be more a bit more prevalent than that.