On Wed, 29 Oct 2014, Arnd Bergmann wrote: > On Wednesday 29 October 2014 13:09:47 Kevin Cernekee wrote: > > generic-chip.c already has a fair amount of indirection, with pointers > > to saved masks, user-specified register offsets, and such. Is there a > > concern that introducing, say, a pair of readl/writel function > > pointers, would cause an unacceptable performance drop? > > I don't know. Thomas' reply suggests that it isn't. Doing byteswap > in software at a register access is usually free in terms of CPU > cycles, but an indirect function call can be noticeable if we do > that a lot. I did not say that it is free. I merily said that I prefer to have this solved at the core level rather than at the driver level. So you have several options to do so: 1) Indirections 2) Different functions for the different access modes 3) Alternatives #1 Is the simplest solution, but imposes the overhead of an indirect function call for something trivial #2 The most efficient and flexible way if you have to provide different access modes for different drivers. But it comes with the price of increasing the text foot print. #3 Smart and efficient, but requires that on a particular system all drivers use the same access mode. Thanks, tglx
