From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: mapping large amount of memory on physical addresses Message-ID: From: scarayol@assystembrime.com Date: Tue, 12 Apr 2005 08:23:46 +0200 MIME-Version: 1.0 Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 8BIT Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org List-ID: Hello, I wrote 2 drivers very close to the driver /dev/mem in order to write in the physical memory at specific addresses. For that I use mmap instruction. I want to know, if there is a limit for the maximum amount of physical memory that I can map with a single the mmap instruction. My platform is a MPC885 (PowerPC) on a MPC885ADS board and I have a 2.4.26 kernel. Now I map 2 zones of 1MB (first zone at 6MB and the 2nd at 7MB:I have 8MB on my board), each on the same physical component (to have data transfertsbetween the two zones). But, in the final application (on our own card) one zone will represent 2MB for a component of 2MB and and the other 216 MB for another component of 256MB. So, it will let 40MB for the kernel, FileSystem, etc. How can I be sure that linux let me reserve all these physical addresses ? If I use the command 'mem=6M' in u-boot to force Linux in the first 6M, the mem driver accesses don't work any more. If mmap doesn't work for such an amount of memory (216 MB) how can I do ? Last question: How could I verify the mapping by a shell command or a memory dump... ? Thank you really for your help. ---------------------------------------------------------- Sophie CARAYOL TECHNOLOGIES & SYSTEMES 50 rue du President Sadate F - 29337 QUIMPER CEDEX Tel: +33 2 98 10 30 06 mailto:scarayol@assystembrime.com ---------------------------------------------------------- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org