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by fellerts 1019 days ago
I was expecting a tale of how the author managed to overwrite whatever part of the monitor's firmware was responsible for spitting out the EDID. While interesting, the title is a bit misleading: it's an ugly but effective hack to inject a custom EDID.
3 comments
Arnavion 1019 days ago
I wouldn't really call it "an ugly hack" since the kernel has had this procedure (to load EDID overrides from /lib/firmware) since forever. Introduced in 2012 by https://github.com/torvalds/linux/commit/da0df92b57311aa1b26... , current doc is in https://github.com/torvalds/linux/blob/872459663c52f5e8a28c0...
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kj800x 1018 days ago
Haha, I'm happy to agree to disagree here. In my book doing hex editing on a binary file and overriding what my system thinks the monitor is reporting to ultimately solve the problem feels enough like a hack (http://catb.org/jargon/html/meaning-of-hack.html).

As someone else noted, I'm considering overwriting the EEPROM in the monitor but I'd like to be 100% certain that's correct before I try it (one of the reasons I posted to HN was to see if folks thought I was going down the wrong path). I'm actually going to try a completely new cable first in case it's a bandwidth issue.

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drivers99 1019 days ago
In the last paragraph: "One last thing I might consider doing at some point would be to try to overwrite the EDID on the monitor itself."
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jauntywundrkind 1019 days ago
And the author downloaded the monitor's edid & bitwrenched it around to make their hack.

I definitely had the same expectation, & was most way through reading, expecting my expectation wasnt going to be mentioned, but I was far from upset. I was quite happy to hear there's kernel workarounds for exactly this kind of thing.

The main shortcoming I feel right now is that this only works if you only have one specific monitor you want to hack, or you are ok rebooting. If the kernel had some way to dynamically override the edid that would be excellent. Maybe a eBPF filter?

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ansible 1019 days ago
On some monitors (more typically the older ones), the EDID is just stored in an I2C EEPROM. So it may be possible to just re-program it. I don't know what they do on newer monitors, it could just be something listening to the I2C in the HDMI connector and pretending to be an EEPROM.
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