(it might not be clear but that thread started when i plugged an apple thunderbolt 3 to thunderbolt 2 adapter into an usb c port on my xps13 laptop and expected it to work. i ended up cutting the adapter open, desoldering the controller, figuring out what industry standard chip…
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Apple remarked with their own p/n, reverse-engineering the adapter and its test points, dumping and reverse-engineering the adapter firmware, obtaining vendor tools for USB C controllers that are for some reason export-controlled and you can't just download them or the docs,
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reflashing the controller, reading the entire USB PD spec, making an USB PD protocol sniffer, dumping the firmware in my laptop, enabling undocumented Intel-only features in vendor tools, figuring out internal Intel politics, and finally pestering at least two Dell people…
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including one that is responsible for the USB PD firmware in my specific laptop... ... and I still don't know why the fuck doesn't the goddamn thing just work.)
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Replying to @whitequark @adipisicing
have you considered just using a wall charger
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Replying to @eevee @adipisicing
no no you don't get it USB power delivery is the part of USB that negotiates Thunderbolt, DisplayPort, etc alternate modes over the USB C connector.
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Thunderbolt has no relationship with USB power delivery per se, they just had an existing protocol so obviously they stuffed it in there.
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Replying to @whitequark @adipisicing
oh okay of course power delivery would be used for displaypoWHAT ARE YOU SAYING TO ME
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Replying to @eevee @adipisicing
you can also use it to reflash the three microchips involved in plugging a Thunderbolt 3 device 40 Gbps into your laptop. two in the cable plugs (they have a little elliptic curve engine, and X.509, inside to prove that the cable passed certification) and one more in the device
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except they realized that sticking three distinct chips into something like a device with a captive cable is silly so you can virtualize two of them inside of the third. there's an option in the vendor tool and everything
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the PD controller in the USB device is called "SOP" in the spec, the one in proximate plug is "SOP-prime" and in the distal plug is "SOP-prime-prime". "SOP" means "start of packet"
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i can continue more or less indefinitely
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