• Jon Mason's avatar
    PCI-Express Non-Transparent Bridge Support · fce8a7bb
    Jon Mason authored
    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: default avatarJon Mason <jon.mason@intel.com>
    Reviewed-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
ntb_transport.c 36.1 KB