>Regarding drivers, they are probably present as linux kernel modules in original phone firmware. Cannot they be reused in a custom open firmware? Generally no

>Regarding drivers, they are probably present as linux kernel modules in original phone firmware. Cannot they be reused in a custom open firmware? Generally not. Linux kernel modules generally can't be loaded by kernels with different versions, as the ABI constantly changes. It can be hard to use them even with the same version, if it was compiled differently. This is why they're always pushing for the drivers to be open-sourced and submitted to the kernel project for inclusion, because maintaining them separately is a giant PITA. Phone makers don't bother because they don't care: they're not going to maintain the drivers very long anyway.