I sent this to alpine-user a few days ago without much luck so I'm trying my chance here.
I have been trying to use alpine linux on a raspberry pi b+ with the raspberry pi touchscreen. While the screen itself is working out of the box I can't manage to get the touchscreen to work, namely I do no get anything in /dev/input/ and the rpi-ft5406 kernel module is no loaded. The same hardware configuration does however work on raspbian. Here are a few things I tried:
1) Directly tried to modprobe rpi_ft5406 evdev. Nothing happens and dmesg doesn't move.
2) Tried to install the touchscreen overlay  on the sdcard in overlays/ and add dtoverlay=rpi-ft5406 to usercfg.txt
3) Tried to dynamically load the same overlay via the dtoverlay tool (available through the raspberry package):
dtoverlay -d /media/mmcblk0p1/overlays/ rpi-ft5406
cp: can't create '/sys/kernel/config/device-tree/overlays/0_rpi-ft5406/dtbo': File exists
* Failed to apply overlay '0_rpi-ft5406'
(The mentioned file does not exist)
In all these cases nothing happens and `dmesg | grep -i ft5406` is empty.
Anybody has a hint ?