On Mon, Mar 15, 2021 at 10:33:13AM -0600, Logan Gunthorpe wrote: > >> + return !ops || ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED; > > > > Is this logic correct? I would have expected. > > > > return (ops && ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED); > > > If ops is NULL then the operations in kernel/dma/direct.c are used and > support is added to those in patch 6. So it is correct as written. It is not quite that easy. There also is the bypass flag and for the specific case where that is ignored the code needs a really good comment. And to assist that formatted so that it makes sense. The above line is indeed highly confusing even if it ends up being correct.
