On Wed, Apr 09, 2014 at 12:39:37AM +0100, Michael Bohan wrote: > On Tue, Apr 08, 2014 at 12:49:49PM +0100, Catalin Marinas wrote: > > On Tue, Apr 08, 2014 at 01:35:47AM +0100, Michael Bohan wrote: > > > How should we handle Device Memory with copy_from_user / copy_to_user? > > > Should we follow the same scheme and create > > > copy_from_user_io / copy_to_user_io, or rather enforce that the stock > > > routines handle alignment? > > > > We have generic copy_from_user_toio() and copy_to_user_fromio(). Are > > these what you need? As with the memcpy_(to|from)io, they can be further > > optimised. > > It seems these existing routines are in sound. Were you thinking > the right approach would be to move them out of sound and make > them per-arch defined? If you have a use-case outside of the sound subsystem, they can be made more generic. > What about the other two use cases: copy_from_user_fromio and > copy_to_user_toio? Are those reasonable to add? These two APIs > would cover the use case I had in mind. What's the use case for these? > Then what about the strange but possible use case where both the > source and destination pointers are iomem? This same question > applies for memcpy_fromio / memcpy_toio as well. You can come up with many combinations but we first need to see a real use of them, eliminate the alternatives and only then look at adding new API. > The implementations of copy_from_user_toio and > copy_to_user_fromio are currently doing a second copy, so that > seems bad for performance. We'd probably want to improve these as > well if others are in agreement. Yes, as I said they are not optimised (but good enough as a start). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
