Re: [PARPORT] DMA and the parallel port

From: Blaise Gassend (
Date: Fri May 02 2003 - 21:38:20 EDT

  • Next message: Bob Tanner: "Re: [PARPORT] DMA and the parallel port"

    > Yes. So, now, what are dma channels? And if my Super IO chip has them, do the
    > low level parallel port driver deal with them? I don't seem to see any
    > functionality in parport or libieee1284 for dealing with dma, so I think it's
    > not something I have to worry about.

    In general there is more than one DMA operation going on at a time (you
    are writing to disk and getting a packet over the network) so there are
    many DMA channels, each of which can be servicing a different
    peripheral. Your chipset certainly has DMA channels, and probably has
    one for the parallel port if it supports ECP (or perhaps EPP, I'm no

    There is some DMA code in parport_pc.c. For writing to the port it works
    well. For reading from the port there is some code that I hacked up that
    is circulating with the CPiA webcam drivers, but it only works for those
    webcams. For the webcam it produces a HUGE improvement in performance.

    What exactly are you trying to do?


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