How do we use the bus_dma interface ?

Pratik Singhal ps06756 at
Wed May 27 14:26:17 UTC 2015

Hello, I have to program the Cubieboard's DMA controller. So far, after the
initialization of the driver, to perform DMA transfer I was trying to pass
the actual physical address to the DMA controller which I came to know
that,  is not the correct way to program the DMA controller. Instead, I
should try using the bus_dma(9)  interface.

I have read the relevant parts of the DMA from the book FreeBSD Device
Driver, but I am unable to understand the bus_dma interface. (How to use it
? ) . Can someone please give a overview of the whole process (tags and
maps)  so that I can at least get started on the programming part.  for ex,
How should I use the interface to start the DMA transfer ?

Pratik Singhal

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