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SubjectRe: alpha iommu fixes
On Sun, May 20, 2001 at 01:16:25PM -0400, Jeff Garzik wrote:
> Andrea Arcangeli wrote:
> >
> > On Sun, May 20, 2001 at 03:49:58PM +0200, Andrea Arcangeli wrote:
> > > they returned zero. You either have to drop the skb or to try again later
> > > if they returns zero.
> >
> > BTW, pci_map_single is not a nice interface, it cannot return bus
> > address 0,
>
> who says?
>
> A value of zero for the mapping is certainly an acceptable value, and it
> should be handled by drivers.

this is exactly why I'm saying pci_map_single currently is ugly in
declaring a retval of 0 as an error, because as you also explicitly said
above bus address 0 is perfectly valid bus adress, so my whole point is
that I'd prefer to change the API of pci_map_single to notify of faliure
not returning 0 like it does right now in 2.4.5pre3 and all previous 2.4
kernels but via a parameter, so bus address zero returns a valid bus
address as it should be just now (but it isn't right now).

> In fact its an open bug in a couple net drivers that they check the
> mapping to see if it is non-zero...

if a driver is catching the faluire of pci_map_single by checking if the
bus address returned is zero such driver is one of the few (or the only
one) correct driver out there.

As it stands right now a bus address of 0 means pci_map_single failed.

For pci_map_sg if it returns zero it means it failed too.

Andrea
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