On Fri, Nov 16, 2012 at 07:27:12PM -0700, Jon Mason wrote: > A PCI-Express non-transparent bridge (NTB) is a point-to-point PCIe bus > connecting 2 systems, providing electrical isolation between the two subsystems. > A non-transparent bridge is functionally similar to a transparent bridge except > that both sides of the bridge have their own independent address domains. The > host on one side of the bridge will not have the visibility of the complete > memory or I/O space on the other side of the bridge. To communicate across the > non-transparent bridge, each NTB endpoint has one (or more) apertures exposed to > the local system. Writes to these apertures are mirrored to memory on the > remote system. Communications can also occur through the use of doorbell > registers that initiate interrupts to the alternate domain, and scratch-pad > registers accessible from both sides. > > The NTB device driver is needed to configure these memory windows, doorbell, and > scratch-pad registers as well as use them in such a way as they can be turned > into a viable communication channel to the remote system. ntb_hw.[ch] > determines the usage model (NTB to NTB or NTB to Root Port) and abstracts away > the underlying hardware to provide access and a common interface to the doorbell > registers, scratch pads, and memory windows. These hardware interfaces are > exported so that other, non-mainlined kernel drivers can access these. > ntb_transport.[ch] also uses the exported interfaces in ntb_hw.[ch] to setup a > communication channel(s) and provide a reliable way of transferring data from > one side to the other, which it then exports so that "client" drivers can access > them. These client drivers are used to provide a standard kernel interface > (i.e., Ethernet device) to NTB, such that Linux can transfer data from one > system to the other in a standard way. > > Signed-off-by: Jon Mason <jon.mason@xxxxxxxxx> > Reviewed-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx> Sorry for the very long delay, I've now applied these two patches, thanks for the cleanups and changes from the original versions. But, I now get the following build warning, so can you send a follow-on patch that fixes it up before you start getting angry emails from the 0-day build bot? drivers/ntb/ntb_transport.c: In function ‘ntb_transport_rx’: drivers/ntb/ntb_transport.c:895:7: warning: ‘offset’ may be used uninitialized in this function [-Wuninitialized] drivers/ntb/ntb_transport.c:891:8: note: ‘offset’ was declared here thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
