Messages in this thread | | | Date | Tue, 31 Jan 2012 13:09:22 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] NVMe: Fix compilation on architecturs without readq/writeq |
| |
* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> > u64 val; > > val = readl(addr); > > val |= readl(addr+4) << 32; > > > > is well-defined and must read the low word first - both at the C level > > *and* at the CPU level. Anything else would be a bug in the > > architecture "readl()" implementation or the hardware. > > That doesn't make the access atomic to hardware however as a true 64bit > readq/writeq would be ? > > It seems to me the two are not quite the same semantically
Correct, and that's what the:
#include <asm/io-inatomic.h>
line in the driver would express.
Thanks,
Ingo
| |