Date: Sun, 08 Nov 2015 13:00:02 +0100 From: AlexHully <deco33000@yandex.com> To: Hans Petter Selasky <hps@selasky.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: dma Message-ID: <373471446984002@web20j.yandex.ru> In-Reply-To: <563F38DD.5070409@selasky.org> References: <298361446978177@web22g.yandex.ru> <563F38DD.5070409@selasky.org>
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Ok, those were recent? --š Alex 08.11.2015, 12:56, "Hans Petter Selasky" <hps@selasky.org>: > On 11/08/15 11:22, AlexHully wrote: >> šHi, >> >> šI would like a clarification for dma. >> >> šThe context: most dma capable devices have 32 bits address range. >> šIs it correct that, if there was no 3G/1G mapping in the kernel, or that kernel low memory could map 4Gb memory, one could choose any free addresses in that low memory to set up a dma buffer? >> >> šThat would avoid all the mapping hassle, and performance cost associated. > > I've seen USB controllers only supporting 2G address range. > > --HPS
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