There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
5 points
Well, the source checks the cable using the CC line which doesn’t go through the cable (VCONN). So source only knows the cable directly plugged in. To make the extension cable visible, the sink would be required to check the cable plugged in using VCONN and then the tell max ampere to the source over the other CC that goes through the cable.
2 Problems:
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Sink devices normally don’t read or can’t read VCONN as far as I know
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No way of detecting if a third cable (extension in the middle) is present and what specs it has
