> On Sun, 2 Jan 2011, loody wrote: > > > Dear all: > > I am trying porting usb on mips platform. > > Due to hw limitation, I have to do the dummy read to make sure data > > has been written to the memory, so I announce an volatile parameter, > > tmp, such that cpu will read the same address back to me. Unfortunately that is not of any use, as you noted. The "volatile" nature of your parameter "tmp" is irrelevant. If you want to prevent the compiler optimising out the read of what you've just written then it's what you just wrote that needs to be "volatile". So if the variable "dummy" is yours, then it should be declared as a pointer-to-volatile-struct rather than just pointer-to-struct. The rule we use in my embedded programming day-job is that any variable that maps a hardware port must be declared volatile, and any pointer used to access a hardware port must be a pointer-to-volatile. I'm sure Alan's solution would be fine. I offer the above comments because the problem may arise outside of an environment where ACCESS_ONCE is available. Cheers, Rob -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
