On 2019-07-25 5:50 a.m., Christoph Hellwig wrote: > On Wed, Jul 24, 2019 at 10:06:22AM -0600, Logan Gunthorpe wrote: >> Yes. This is the downside of dealing only with a phys_addr_t: we have to >> look up against it. Unfortunately, I believe it's possible for different >> BARs on a device to be in different windows, so something like this is >> necessary unless we already know the BAR the phys_addr_t belongs to. It >> might probably be sped up a bit by storing the offsets of each bar >> instead of looping through all the bridge windows, but I don't think it >> will get you *that* much. >> >> As this is an example with no users, the answer here will really depend >> on what the use-case is doing. If they can lookup, ahead of time, the >> mapping type and offset then they don't have to do this work on the hot >> path and it means that pci_p2pdma_map_resource() is simply not a >> suitable API. > > Ok. So lets just keep this out as an RFC and don't merge it until an > actual concrete user shows up. Yup, that was my intention and I mentioned that in the commit message. Logan
