On Thu, Dec 14, 2006 at 10:56:03AM +0100, Hans-Jürgen Koch wrote:
> A small German manufacturer produces high-end AD converter cards. He sells
> 100 pieces per year, only in Germany and only with Windows drivers. He would
> now like to make his cards work with Linux. He has two driver programmers
> with little experience in writing Linux kernel drivers. What do you tell him?
> Write a large kernel module from scratch? Completely rewrite his code
> because it uses floating point arithmetics?
Write a small kernel module which:
- create a device node per-card
- read the data from the A/D as fast as possible and buffer it in main
memory without touching it
- implements a read interface to read data from the buffer
- implement ioctls for whatever controls you need
And that's it. All the rest can be done in userspace, safely, with
floating point, C++ and everything. If the driver programmers are
worth their pay, their driver is probably already split logically at
where the userspace-kernel interface would be.
And small means small, like 200 lines or so, more if you want to have
fun with sysfs, poll, aio and their ilk, but that's not a necessity.
OG.
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