Re: [PATCH 2/3] i386: add io_map_cached

[Samuel Thibault]

Justus Winter, le Thu 15 May 2014 12:32:41 +0200, a écrit :
> Quoting Samuel Thibault (2014-05-15 02:13:13)
> > Justus Winter, le Fri 02 May 2014 21:33:01 +0200, a écrit :
> > > io_map_cached is like io_map, but reuses the old mapping if it is
> > > applicable.
> > 
> > But AIUI, if it is not applicable, it does not unmap the previous
> > mapping, so we lose virtual memory.
> > 
> > A really transparent io_map_cached seems not really feasible, since you
> > never know what the caller will do with the pointer.
> 
> Right, I did this b/c I didn't know how to do this properly.

> accessing this physical address with phystokv() fails b/c it is
> outside the mapped range

Ok. I'd say then to just use io_map once for accessing that (AIUI one
knows the needed size), and then free the mapped memory region after
that with kmem_free.

Samuel