Messages in this thread | | | Date | Mon, 10 Aug 2009 21:50:48 +0200 | From | "Emilio G. Cota" <> | Subject | Re: [patch 1/5] Staging: VME Framework for the Linux Kernel |
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Martyn Welch wrote: > If the driver writer wants a "single shot" effect, there's little > overhead in creating a one item link-list and executing it. However, > without support for this mode the author is stuck with single shot > transfers. If the author wants to perform scatter gather type > transfers, without this functionality in the API - which is supported by > all the bridges I have seen - he won't be able to easily avail himself > of this functionality and get "work done".
Again, he (the driver writer) should know *nothing* about that.
As for the scatter-gather case, what should happen is:
User: hey, there's a buffer I want to transfer. here's a pointer and size VME layer: ok, passing it to the bridge VME bridge: I know I'm over PCI, so I'll get the pages from memory and map the sg list over PCI, and then will tell the bridge to perform from there.
That's just a particular example, but for the user (read driver writer) it's much simpler this way. Doesn't need to know about lists or whatever.
E.
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