Subject: Re: New i2c framework
To: Eduardo Horvath <eeh@NetBSD.ORG>
From: Jason Thorpe <firstname.lastname@example.org>
Date: 07/31/2003 09:01:08
On Thursday, July 31, 2003, at 08:43 AM, Eduardo Horvath wrote:
> But they are separate address spaces, so don't you need some way to
> differentiate between communications to a 7-bit device or a 10-bit
> device at the same address?
I need to reread the I2C spec before I can answer this question.
> Huh? How does that prevent you from doing direct configuration?
Direct configuration requires being able to deterministically identify
a device based on some unique cookie. I2C does not have that.
Chris's suggestion of a hybrid approach using a platform-specific table
could be useful, but pure direct configuration like is possible on e.g.
SBus or PCI is simply not possible on I2C.
> So... How does a userland program issue commands that require
> repeated starts?
With regard to more complex operations being directed by userspace,
I've been toying with the idea of a "scripted" API that userland could
use (I actually implemented a "scripted" API for kernel drivers
originally, but it was a bit too complicated to use :-)
In any case, I don't want to gate this on the userland API. I consider
that piece a moving target at this point, and it really has no direct
bearing on the API used within the kernel.
-- Jason R. Thorpe <email@example.com>