how to read/write registers of CPU or Device from user space

Hi, all,

when debugging kernel or driver, we need to read/write registers of CPU and devices. I wanna use /dev/mem to do, is it possible? if need to do others things? is it better to write a driver for read/write CPU/device's registers by myself?

Do you have any good advice?

Thanks in advance!
John

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/