NTB: Add NTB hardware abstraction layer
Abstract the NTB device behind a programming interface, so that it can
support different hardware and client drivers.
Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
diff --git a/Documentation/ntb.txt b/Documentation/ntb.txt
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+# NTB Drivers
+
+NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
+the separate memory systems of two computers to the same PCI-Express fabric.
+Existing NTB hardware supports a common feature set, including scratchpad
+registers, doorbell registers, and memory translation windows. Scratchpad
+registers are read-and-writable registers that are accessible from either side
+of the device, so that peers can exchange a small amount of information at a
+fixed address. Doorbell registers provide a way for peers to send interrupt
+events. Memory windows allow translated read and write access to the peer
+memory.
+
+## NTB Core Driver (ntb)
+
+The NTB core driver defines an api wrapping the common feature set, and allows
+clients interested in NTB features to discover NTB the devices supported by
+hardware drivers. The term "client" is used here to mean an upper layer
+component making use of the NTB api. The term "driver," or "hardware driver,"
+is used here to mean a driver for a specific vendor and model of NTB hardware.
+
+## NTB Client Drivers
+
+NTB client drivers should register with the NTB core driver. After
+registering, the client probe and remove functions will be called appropriately
+as ntb hardware, or hardware drivers, are inserted and removed. The
+registration uses the Linux Device framework, so it should feel familiar to
+anyone who has written a pci driver.
+
+## NTB Hardware Drivers
+
+NTB hardware drivers should register devices with the NTB core driver. After
+registering, clients probe and remove functions will be called.