It turns out that it's also really easy on slackwareARM. The fbi package is not necessary as it's just for displaying images on the lcd itself.
Add the spi modules to /etc/rc.d/rc.modules.local
Code:
/sbin/modprobe spi_bcm2835
Add this line to the end of /boot/config.txt
Code:
dtoverlay=piscreen,speed=16000000
Reboot the rpi and you should already see /dev/fb1
Modify /etc/X11/xorg.conf.d/xorg.conf to look like this:
Code:
Section "Device"
Identifier "Allwinner A10/A13 FBDEV"
Driver "fbturbo"
Option "fbdev" "/dev/fb1"
Option "SwapbuffersWait" "true"
EndSection
Add a line like this to xinitrc before the window manager is started (for example in /etc/X11/xinit/xinitrc.blackbox)
Code:
xinput set-prop 'ADS7846 Touchscreen' 'Coordinate Transformation Matrix' 1 0 0 0 -1 1 0 0 1
This will rotate the touchscreen so that it matches the display (alternatively you can rotate the display in /boot/config.txt but I prefer to have the HDMI, audio jack and power pointing up).
Restart X and you should get output on the 3.5 inch lcd.
If something goes wrong (and you still have the HDMI monitor connected) pres CTRL^ALT^F1 and you get the text console to mend things without needing network access to the pi.
Does anyone know how to get the FB console also working on this display ?