Date: Thu, 14 Dec 2006 12:51:05 +0100
From: Olivier Galibert <galibert@pobox.com>
To: linux-kernel@vger.kernel.org
Subject: Re: [GIT PATCH] more Driver core patches for 2.6.19
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On Thu, Dec 14, 2006 at 10:56:03AM +0100, Hans-J?rgen 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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