On Tuesday 10 April 2012, Marek Szyprowski wrote:
Before patch no 6, there were custom methods for all scatter/gather related operations. They iterated over the whole scatter list and called cache related operations directly (which in turn checked if we use dma bounce code or not and called respective version). Patch no 6 changed them not to use such shortcut for direct calling cache related operations.
Instead it provides similar loop over scatter list and calls methods from the current device's dma_map_ops structure. This way, after patch no 7 these functions call simple dma_map_page() method for all standard devices and dma bounce aware version for devices registered for dma bouncing (with use different dma_map_ops).
Ok, thanks for the explanation.
I can provide a separate set of scatter/gather list related functions for the linear dma mapping implementation and dma bouncing implementation if you think that the current approach is too complicated or over-engineered.
It's probably not needed, though I have not looked at the big picture with all the patches applied. which I should do at some point.
Arnd