forked from Minki/linux
e26a5843f7
Change ntb_hw_intel to use the new NTB hardware abstraction layer. Split ntb_transport into its own driver. Change it to use the new NTB hardware abstraction layer. Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com> Signed-off-by: Jon Mason <jdmason@kudzu.us>
59 lines
2.8 KiB
Plaintext
59 lines
2.8 KiB
Plaintext
# NTB Drivers
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NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
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the separate memory systems of two computers to the same PCI-Express fabric.
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Existing NTB hardware supports a common feature set, including scratchpad
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registers, doorbell registers, and memory translation windows. Scratchpad
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registers are read-and-writable registers that are accessible from either side
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of the device, so that peers can exchange a small amount of information at a
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fixed address. Doorbell registers provide a way for peers to send interrupt
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events. Memory windows allow translated read and write access to the peer
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memory.
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## NTB Core Driver (ntb)
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The NTB core driver defines an api wrapping the common feature set, and allows
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clients interested in NTB features to discover NTB the devices supported by
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hardware drivers. The term "client" is used here to mean an upper layer
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component making use of the NTB api. The term "driver," or "hardware driver,"
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is used here to mean a driver for a specific vendor and model of NTB hardware.
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## NTB Client Drivers
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NTB client drivers should register with the NTB core driver. After
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registering, the client probe and remove functions will be called appropriately
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as ntb hardware, or hardware drivers, are inserted and removed. The
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registration uses the Linux Device framework, so it should feel familiar to
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anyone who has written a pci driver.
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### NTB Transport Client (ntb\_transport) and NTB Netdev (ntb\_netdev)
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The primary client for NTB is the Transport client, used in tandem with NTB
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Netdev. These drivers function together to create a logical link to the peer,
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across the ntb, to exchange packets of network data. The Transport client
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establishes a logical link to the peer, and creates queue pairs to exchange
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messages and data. The NTB Netdev then creates an ethernet device using a
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Transport queue pair. Network data is copied between socket buffers and the
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Transport queue pair buffer. The Transport client may be used for other things
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besides Netdev, however no other applications have yet been written.
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## NTB Hardware Drivers
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NTB hardware drivers should register devices with the NTB core driver. After
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registering, clients probe and remove functions will be called.
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### NTB Intel Hardware Driver (ntb\_hw\_intel)
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The Intel hardware driver supports NTB on Xeon and Atom CPUs.
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Module Parameters:
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* b2b\_mw\_idx - If the peer ntb is to be accessed via a memory window, then use
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this memory window to access the peer ntb. A value of zero or positive
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starts from the first mw idx, and a negative value starts from the last
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mw idx. Both sides MUST set the same value here! The default value is
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`-1`.
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* b2b\_mw\_share - If the peer ntb is to be accessed via a memory window, and if
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the memory window is large enough, still allow the client to use the
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second half of the memory window for address translation to the peer.
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