Comment by laborat

I guess these guys hadn't seen the info on https://linux-sunxi.org/Main_Page when they were trying to get the device to run arbitrary code. All Allwinner SoCs have a USB bootloader baked into the _CPU_, which you can talk to over an open-source protocol (poorly documented, but on my old A10 tablet the magic term to google for is 'LiveSuit' - there is an open-source Linux driver, bootloader, and flasher stub to be found on github somewhere).