Re: Allocating Page Aligned Memory in User Space

From: David Schwartz (davids_at_webmaster.com)
Date: 08/28/03 

Date: Wed, 27 Aug 2003 15:22:51 -0700

"Thomas Richter" <thor@cleopatra.math.tu-berlin.de> wrote in message
news:bifh1s$ngu$1@mamenchi.zrz.TU-Berlin.DE...

> > I have a program that I'm writing to interface with a driver that
> > controls an IO board. In order to take the data from the driver and
> > DMA it to another IO device (IDE drive) I need to have the data DMA
> > page aligned. So, I'm pretty sure it can be a 32-bit address, but the
> > data needs to be on a 64k boundary along with the PRD (Physical Region
> > Descriptor) entries which will hold pointers to these data chunks.

    Follow the driver documentation.

> > Does anyone know how to allocate memory like this without having to
> > write a (kernel level) driver?

    The driver documentation must tell you how to do this. If it doesn't,
the documentation and/or the driver is broken.

> Simple. Allocate 64K more memory as required,
> then align the returned memory address "upwards" to the next 64K boundary.

    No good. Do it the way the driver author intended, follow the reference
code. If the driver is broken, fix it.

    DS

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