Yep, I've just finished rewriting touchscreen and battery drivers to use s3c24xx_adc driver instead using adc directly. It was relatively easy :)
No more adc_battery driver (s3c24xx_adc is not adc-class compliant, and I was too lazy to port adc-class to 2.6.28). I rewrote adc_battery to use s3c24xx_adc driver directly, and named it s3c_adc_battery :)
And with touchscreen it was much easier: just add some #includes, add adc_client field to device struct, add 2 callback implementations, add some lines about registering as adc_client, and replace some lines that start adc conversion... That's all.
Patch is available here
P.S. It seems touchscreen driver needs some filtering... I'll look what openmoko guys made to implement touchscreen filtering.