Date: Sun, 31 Jan 1999 06:52:25 -0800 From: Mike Smith <mike@smith.net.au> To: wschlanger@usa.net, hackers@FreeBSD.ORG Subject: Re: ISA limmitation of 16MB for DMA [wschlanger@usa.net: ] Message-ID: <199901311452.GAA06506@dingo.cdrom.com> In-Reply-To: Your message of "Sun, 31 Jan 1999 05:21:09 %2B0100." <19990131052109.A1053@panke.de.freebsd.org>
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FreeBSD uses the time-honoured technique of "bounce buffering" - it maintains a pool of buffers in ISA-addressable space, and allocates them as required to back pending ISA busmaster transactions. This is handled transparently by the bus-space DMA code, which adds several levels of indirection to the issue. You may find the older kernels (2.2.x) technique which involved explicit cooperation by the driver easier to understand. > ----- Forwarded message from Willow Schlanger <wschlanger@usa.net> ----- > > Thanks. Would you happen to know where I can learn how FreeBSD gets > around the ISA limmitation of 16MB for DMA? Is there a source file I can > see that demonstrates this? > > Thanks in advance, > Willow Schlanger > > Wolfram Schneider wrote: > > > > On 1999-01-24 03:49:02 -0800, Willow Schlanger wrote: > > > Q: Hi. I'm a programmer and I'm interested in the kernel source code for > > > FreeBSD. I can't seem to find it anywhere - I've tried different FTPs > > > FreeBSD.org mentions, but I can never figure them out. I use DOS and > > > Windows 95/98 -- do I need some special program to get the assembly > > > language and C/++ sources? > > > > [cc: freebsd-questions] > > > > The FreeBSD kernel sources code is available at > > > > ftp://ftp.freebsd.org/pub/FreeBSD/FreeBSD-current/src/sys > > > > or > > http://www.freebsd.org/cgi/cvsweb.cgi/src/sys > > > > > > > > Can you help me? > > > > > > Thanks in advance, > > > Willow Schlanger > > > > -- > > Wolfram Schneider <wosch@freebsd.org> http://freebsd.org/~w/ > > ----- End forwarded message ----- > > -- > Wolfram Schneider <wosch@freebsd.org> http://freebsd.org/~w/ > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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