From: Jiri Slaby <jirislaby@gmail.com>
To: Francis Moreau <francis.moro@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Question about DMA
Date: Sun, 27 Jan 2008 23:34:08 +0100 [thread overview]
Message-ID: <479D06E0.3090601@gmail.com> (raw)
In-Reply-To: <38b2ab8a0801271251v1a9ea256w8fa4b9fcc620f742@mail.gmail.com>
On 01/27/2008 09:51 PM, Francis Moreau wrote:
> Hello,
>
> I have 2 questions regarding set_dma_addr(unsigned int channel,
> unsigned int addr) helper.
>
> 1/ Why does the function take only one address ? I would expect it
> to take both a source and a destination address for the dma controller
> to transfer data.
since your device is responsible for sending data from/to local memory. ISA dma
controller has only 2 registers -- 16-bit address to put incoming data to (get
outcoming from) + 8-bit nonincrementing page and 16-bit counter.
> 2/ The type of address parameter is an unsigned int. Why isn't it a dma_addr_t
> type ?
since isa dma controller can address up to 2^24 (16-bit address + 8-bit page)
bytes of memory, i.e. 16M.
Are you sure, you want use this API?
next prev parent reply other threads:[~2008-01-27 22:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-27 20:51 Question about DMA Francis Moreau
2008-01-27 22:34 ` Jiri Slaby [this message]
2008-01-28 8:55 ` Francis Moreau
2008-01-28 9:04 ` Jiri Slaby
2008-01-28 10:20 ` Francis Moreau
2008-01-28 9:21 ` Haavard Skinnemoen
2008-01-28 10:22 ` Francis Moreau
2008-01-28 10:29 ` Haavard Skinnemoen
2008-01-28 10:40 ` Francis Moreau
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