> MDIO bus controllers are in a similar situation (with Hubert's patch) > but at least there the frame size is fixed and I haven't heard of an > MDIO controller to use DMA.
Linux does not have any DMA driver MDIO busses, as far as i know. It does not make sense, since you are only transferring 16bits of data. The vast majority are polled completion, but there is one which generates an interrupt on completion. Andrew