Hi Bart, > -----Original Message----- > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma- > owner@xxxxxxxxxxxxxxx] On Behalf Of Bart Van Assche > Sent: Monday, March 6, 2017 6:36 PM > To: Doug Ledford <dledford@xxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Sebastian Ott > <sebott@xxxxxxxxxxxxxxxxxx>; Parav Pandit <parav@xxxxxxxxxxxx>; linux- > rdma@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Bart Van Assche > <bart.vanassche@xxxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; > Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>; David Woodhouse > <dwmw2@xxxxxxxxxxxxx>; H . Peter Anvin <hpa@xxxxxxxxx>; Ingo Molnar > <mingo@xxxxxxxxxx>; Russell King <linux@xxxxxxxxxxxxxxx> > Subject: [PATCH 1/2] device: Stop requiring that struct device is embedded in > struct pci_dev > > The dma mapping operations of several architectures and also of several I/O > MMU implementations need to translate a struct device pointer into a struct > pci_dev pointer. This translation is performed by to_pci_dev(). That macro > assumes that struct device is embedded in struct pci_dev. However, that is > not the case for the device structure in struct ib_device. Since that device Why can't ib subsystem pass device structure that is embedded in pci_dev when it makes calls to dma_map APIs? The whole point of clean up was to avoid an if() condition in hot datapath. If we invoke dma_map_ and friend functions with right device, shouldn't it work? That avoids the if() condition as well and avoids changing core of Linux like done in this bug fix. I think ib_device should store the right struct device pointer that needs to go to dma_apis, rather than including pci_dev structure pointer in device core layer. Pseudo example code: struct ib_device { struct device *dma_device; }; ib_dma_unmap_single() which had if(), that got removed with dma_unmap_single() with cleanup patch. Instead of, static inline void ib_dma_unmap_single(struct ib_device *dev, u64 addr, size_t size, enum dma_data_direction direction) { dma_unmap_single(&dev->dev, addr, size, direction); } Why can't we do this? static inline void ib_dma_unmap_single(struct ib_device *dev, u64 addr, size_t size, enum dma_data_direction direction) { dma_unmap_single(dev->dma_device, addr, size, direction); } This avoids increasing all device size by 8 bytes in system. It also clean approach where core device structure doesn't have to bother for pci_dev. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
