Date: Tue, 02 Dec 1997 10:32:52 +1030 From: Mike Smith <mike@smith.net.au> To: "Fred L. Templin" <templin@erg.sri.com> Cc: "John S. Dyson" <toor@dyson.iquest.net>, freebsd-hackers@freebsd.org Subject: Re: copyout()/copyin() Message-ID: <199712020002.KAA00691@word.smith.net.au> In-Reply-To: Your message of "Mon, 01 Dec 1997 13:13:57 -0800." <199712012114.NAA10819@grayling.erg.sri.com>
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This is kinda interesting stuff; I'm just about to launch into the design of a PCI adapter and driver that would ideally be able to do this... > This is essentially what I'm doing right now; I basically only copy the data > when driven by the process - either as the result of a synchronous syscall or > after the kernel wakes the process up after an asynchronous event. The > disadvantage is that I'd really like to move the data directly between the > user buffers and device memory; bypassing kernel memory altogether (I know; I > failed to mention this in my original message!) Which brings us to: What sort of timing granularity and latency can you accept? If you're not too bothered about latency just have the read/write call sleep and wake it out of your interrupt handler. Then traverse the uio manually using the fu*/su* functions. mike
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