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Re: Open Firmware: claiming and mapping memory

From: Hollis Blanchard
Subject: Re: Open Firmware: claiming and mapping memory
Date: Sun, 5 Sep 2004 14:49:00 -0500

On Sep 5, 2004, at 4:30 AM, Marco Gerards wrote:

FYI, the linux loader didn't need any modifications other than adding
a "map" call-method in addition to the current "claim".

Perhaps it would be better to change claim so it checks for a buggy
claim.  What do you think about that?

What do you mean by "buggy claim"? There are two operations
you must perform before using memory: claim, which notifies other potential users (e.g OF or the Linux kernel) that those physical addresses are in use; and map, which allows us to actually touch those addresses we claimed.

IEEE1275 Appendix A's description of "claim" states this explicitly: "Claim does not automatically create an address translation for the allocated resource. See 3.6.5". The reason that confuses me is that 3.6.5's description of claim says the first argument is a "virtual" address...

Ah. The trouble may be that there are two "claim" words. One is generic, and one is a method of of the MMU package. I suspect the MMU's claim will both reserve and map the region requested. I'll try this out later, or maybe tomorrow...


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