question about writing to memory directly from user space in Linux

[Stefan Nickl]

On Wed, 2005-03-23 at 09:10 -0800, Eugene Surovegin wrote:
> On Wed, Mar 23, 2005 at 10:46:45AM +0100, Stefan Nickl wrote:
> > On Wed, 2005-03-23 at 14:25 +0530, Vijay Padiyar wrote:
> > > Can you suggest some kind of a "synchronization" function which I can call
> > > from *user space* which will ensure that all values written to mmaped memory
> > > locations from user space are actually flushed to their physical locations?
> > > I think this might be a potential problem with my code.
> > 
> > Have a look at linux/include/asm-ppc/{io.h,system.h} and
> > http://www.xml.com/ldd/chapter/book/ch08.html
> > 
> > The eieio instruction doesn't need supervisor rights.
> 
> eieio is a nop on 603e core.

Interesting, I was not aware of this.

eieio is handled differently between MPC8245 and MPC8260.

Anyways, it's a non-issue as IO memory should have the right WIMG bits
set to take care of this, and modelling it with a in-kernel i2c bus as
suggested on the list is soo much nicer.

-- 
Stefan Nickl
Kontron Modular Computers