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From: Filipe Araujo <filipius@mercurio.uc.pt>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: DMA
Date: Mon, 18 Nov 1996 16:41:32 +0100
Organization: Lab. Redes de Alta Velocidade - DEE - FCTUC
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Message-ID: <329083AC.7048@mercurio.uc.pt>
References: <328C8861.48A3@mercurio.uc.pt> <56mjnr$b4a@uriah.heep.sax.de>
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To: Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de>
J Wunsch wrote:
> What DMA? ISA motherboard DMA? See the isa_dma_* functions in
> sys/i386/isa/isa.c.
>
To tell the truth I'm not sure. I'm developping a device-driver
for a PCI network adapter and I believe it does busmaster DMA.
> Busmaster DMA is more tricky. I don't think there's a description
> available yet... Perhaps you should bug the developers to write one,
> and volunteer to contribute man pages for the PCI DMA handling. :)
>
> --
> cheers, J"org
>
> joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
> Never trust an operating system you don't have sources for. ;-)
I believe I must follow these steps:
- allocate contiguous memory under 16 MB;
- give the physical addresses (and sizes) to the adapter;
- lock the corresponding pages in central memory (how?);
The adapter is now able to perform DMA.
Is this correct?
Thank you very much.
Filipe Machado de Araujo
Departamento de Engenharia de Informatica
Faculdade de Ciencias e Tecnologia
Universidade de Coimbra
Portugal