Re: [PATCH] PCI: endpoint: pci-epf-test: Roll back BAR mapping when subrange setup fails

[Christian Bruel]

> > > I think "modify TEST_F to SKIP if ENOSPC",
> > > since it will solve the problem for all platforms that have few 
> > > inbound iATUs.
> >
> > That sounds like the right direction, though I think we would first 
> > need a way
> > to propagate -ENOSPC back to the host side, instead of just collapsing 
> > all
> > EP-side setup failures into STATUS_BAR_SUBRANGE_SETUP_FAIL, which
> > pci_endpoint_test currently maps to -EIO.
>
> I think the epf test function can return several bits in the status 
> mask, in addition of STATUS_BAR_SUBRANGE_SETUP_FAIL. e.g 
> STATUS_BAR_SUBRANGE_SETUP_SKIP, or STATUS_BAR_SUBRANGE_SETUP_NOSPC.
> I prefer the former since we want to pass the cause, not the action and 
> let the skip decision to the host

Rethinking this, having a pci_epc_feature to limit the maximum number of 
simultaneously allocatable BARs might be a useful addition to the EPC 
driver. The epc driver would need to keep track of the allocated BARs 
and check it before calling set_bar() for skipping or not.

Do you think this added (minor) complexity is worth it compared to 
simply returning ENOSPC in the status?

thank you,

Christian