Date: Thu, 29 Nov 2001 15:34:15 -0600 (CST) From: mark tinguely <tinguely@web.cs.ndsu.nodak.edu> To: freebsd-hackers@FreeBSD.ORG, zzhang@cs.binghamton.edu Subject: Re: contiguous memory of a buffer Message-ID: <200111292134.fATLYFn42233@web.cs.ndsu.nodak.edu> In-Reply-To: <Pine.SOL.4.21.0111291508440.4208-100000@onyx>
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> I am wondering whether we need contiguous memory for a PHYSICAL buffer to > perform the DMA I/O. yes. The DMA request should either not cross a physical page or if the request does cross a physical page, those pages must be contiguous. the exception to this is if your DMA card has a memory management unit, and you are sharing the same virtual to physical map with the MMU and the host memory allocation space (for a driver, the kernel physical map). --mark tinguely. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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