On Fri, Feb 20, 2009 at 12:57:36PM -0600, Matt Sealey wrote: > Hi guys, > > What's the correct way to read from PCI address space (basically it's > guaranteed to be non-coherent memory bar) without flipping bits like > ioread32() does? > > I need to be able to copy a bank of registers from PCI address space > into a temporary buffer so I can compare them in userspace through > UIO. Because of the flipping and the difference between the original > kernel driver (which used ioread32() and therefore "saw" big endian) > and the userspace app (which has a direct view of the PCI space, and > therefore "sees" little endian) I decided to give userspace an > absolutely consistent little-endian view seeing as this may get ported > to ARM in the coming months. > > I want to put as little code in there as possible and not laboriously > manually flip from my ioread32() big endian values to little endian > again (waste of time and code) if I can help it. Being able to read > the raw value would help a lot, and if I need to do calculations on a > small portion of the data then I can do the flips manually then (using > le32_to_cpu and cpu_to_le32 which will be a noop on ARM), reducing the > amount of porting I need to do in both kernel and userspace alike. > > So, is there something like a direct ioread32le() or so, which will > not change behaviour across architectures, is present on ARM and PPC, > and will handle both PCI address space, and "normal" "ioremapped" > memory? >
I'm pretty sure memcpy_fromio() and memcpy_toio() will get you what you want. They don't change byte ordering. Ira _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
