Some time ago, I knew I needed to write such a driver. But I could not find a web page anywhere describing how to make a start, and there was little help to be found. I would have been happy with a driver for a different ADC, which I would have adapted. But there was none to be found. I searched embedded system mailing lists, and tried to join at least one, unsuccessfully. It all became very difficult.
Usual disclaimers. I wrote this code in a hurry, and it only started to work properly after I'd spent too much time on it already, so I have not neatened it up to the point it should be from some viewpoints. But I have enough interest to put a web page around it. My objective is not to put out good code, but provide a better start than I had.
So, here's a driver. If you're trying to write another driver, the code will no doubt be confusing, I'd suggest you get hold of an ADC7841 and the data sheet for your target analogue-digital converter.
But you now have a better start than I did !
Within reason, I might answer a few questions, and if you're doing something seriously, perhaps you'd like to hire me :)
There are two short programs, which I thought I'd put in as text files, they're not worth compressing or what have you.
A user space program to read driver (adcread.c)
Have fun !