Re: Can I get 200M contiguous physical memory?

From: Nate Edel
Date: Thu Mar 10 2005 - 14:26:01 EST

From: "Arjan van de Ven" <arjan@xxxxxxxxxxxxx>
To: "Jason Luo" <abcd.bpmf@xxxxxxxxx>
A data acquisition card. In DMA mode, the card need 200M contiguous
memory for DMA.

(or want to reserve memory at the boot commandline and then do really
really evil hacks)

Such as booting the machine with "mem=(real memory - 200)M" and then just doing an ioremap of the top 200M of memory.

It's not the most elegant way of doing things given that it requires user intervention at boot time, but I'm not sure it counts as a "really evil hack." Code-wise it's very simple - there's sample code in a couple of the in-RAM MTD(*) drivers you can use as a model. I'm not sure if this method will translate easily to non-x86 platforms if that's an issue.

(* /drivers/mtd/devices/slram.c and /drivers/mtd/devices/mtdram.c ; I'm not sure which of these is more up to date.)

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