Messages in this thread | | | Date | Fri, 16 May 2008 09:10:19 +0100 | From | Jeremy Fitzhardinge <> | Subject | Re: How to avoid data copies in a driver ? |
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Francis Moreau wrote: > I'm suprised because what I need doens't seem so uncommon, usually > devices send or > receive data to/from files. So a helper (system call ?) to achieve > that other than the basic > read/write seems needed, no ? >
It's fairly rare to have an application which requires moving data to file with absolutely no processing; normally there's at least a bit of massaging/parsing/etc. If that's really what you want to do, maybe you can do it with splice? I haven't looked at it at all, but the intention is that you can splice file descriptors together, so you can splice your device fd to a file fd and have it all just work...
Alternatively you could read() from your device into a mmaped file. That's a single copy from device to file, which is about the best you can do without going to heroic lengths.
Also, it really depends on your application. Is it a high-bandwidth thing in which the copy is a huge cost? Or do you want to eliminate the copies because it seems like a nice thing to do?
J
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