Date: Mon, 27 Aug 2001 09:43:54 -0700 From: Julian Elischer <julian@elischer.org> To: Zhihui Zhang <zzhang@cs.binghamton.edu> Cc: freebsd-hackers@freebsd.org Subject: Re: ata0-master: non aligned DMA transfer attempted Message-ID: <3B8A78CA.A888C9BC@elischer.org> References: <Pine.SOL.4.21.0108271015520.14303-100000@onyx>
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Zhihui Zhang wrote:
> I believe that message is from ata_dmasetup():
>
> if (((uintptr_t)data & scp->alignment) || (count & scp->alignment)) {
> ata_printf(scp, device, "non aligned DMA transfer attempted\n");
> return -1;
> }
>
> The user address obtained by static allocation is not 16-byte aligned. The
> kernel routine physio() grabs a physical buffer to do DMA, but it still
> uses the user's address. The KVA associated with the buffer is not used.
>
> -Zhihui
the physical address of a buffer will have the same allignment as the KVA
address.
--
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