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authorLinus Torvalds <torvalds@linux-foundation.org>2017-07-15 12:58:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-15 12:58:58 -0700
commit486088bc4689f826b80aa317b45ac9e42e8b25ee (patch)
treeadf5847a6119d24da990d9e336f005c4a316e6be /Documentation/ntb.txt
parent52f6c588c77b76d548201470c2a28263a41b462b (diff)
parent43e5f7e1fa66531777c49791014c3124ea9208d8 (diff)
Merge tag 'standardize-docs' of git://git.lwn.net/linux
Pull documentation format standardization from Jonathan Corbet: "This series converts a number of top-level documents to the RST format without incorporating them into the Sphinx tree. The hope is to bring some uniformity to kernel documentation and, perhaps more importantly, have our existing docs serve as an example of the desired formatting for those that will be added later. Mauro has gone through and fixed up a lot of top-level documentation files to make them conform to the RST format, but without moving or renaming them in any way. This will help when we incorporate the ones we want to keep into the Sphinx doctree, but the real purpose is to bring a bit of uniformity to our documentation and let the top-level docs serve as examples for those writing new ones" * tag 'standardize-docs' of git://git.lwn.net/linux: (84 commits) docs: kprobes.txt: Fix whitespacing tee.txt: standardize document format cgroup-v2.txt: standardize document format dell_rbu.txt: standardize document format zorro.txt: standardize document format xz.txt: standardize document format xillybus.txt: standardize document format vfio.txt: standardize document format vfio-mediated-device.txt: standardize document format unaligned-memory-access.txt: standardize document format this_cpu_ops.txt: standardize document format svga.txt: standardize document format static-keys.txt: standardize document format smsc_ece1099.txt: standardize document format SM501.txt: standardize document format siphash.txt: standardize document format sgi-ioc4.txt: standardize document format SAK.txt: standardize document format rpmsg.txt: standardize document format robust-futexes.txt: standardize document format ...
Diffstat (limited to 'Documentation/ntb.txt')
-rw-r--r--Documentation/ntb.txt58
1 files changed, 39 insertions, 19 deletions
diff --git a/Documentation/ntb.txt b/Documentation/ntb.txt
index a5af4f0159f3..a043854d28df 100644
--- a/Documentation/ntb.txt
+++ b/Documentation/ntb.txt
@@ -1,4 +1,6 @@
-# NTB Drivers
+===========
+NTB Drivers
+===========
NTB (Non-Transparent Bridge) is a type of PCI-Express bridge chip that connects
the separate memory systems of two or more computers to the same PCI-Express
@@ -12,7 +14,8 @@ special status bits to make sure the information isn't rewritten by another
peer. 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)
+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
@@ -20,7 +23,8 @@ 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
+==================
NTB client drivers should register with the NTB core driver. After
registering, the client probe and remove functions will be called appropriately
@@ -28,7 +32,8 @@ 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 Typical client driver implementation
+NTB Typical client driver implementation
+----------------------------------------
Primary purpose of NTB is to share some peace of memory between at least two
systems. So the NTB device features like Scratchpad/Message registers are
@@ -109,7 +114,8 @@ follows:
Also it is worth to note, that method ntb_mw_count(pidx) should return the
same value as ntb_peer_mw_count() on the peer with port index - pidx.
-### NTB Transport Client (ntb\_transport) and NTB Netdev (ntb\_netdev)
+NTB Transport Client (ntb\_transport) and NTB Netdev (ntb\_netdev)
+------------------------------------------------------------------
The primary client for NTB is the Transport client, used in tandem with NTB
Netdev. These drivers function together to create a logical link to the peer,
@@ -120,7 +126,8 @@ Transport queue pair. Network data is copied between socket buffers and the
Transport queue pair buffer. The Transport client may be used for other things
besides Netdev, however no other applications have yet been written.
-### NTB Ping Pong Test Client (ntb\_pingpong)
+NTB Ping Pong Test Client (ntb\_pingpong)
+-----------------------------------------
The Ping Pong test client serves as a demonstration to exercise the doorbell
and scratchpad registers of NTB hardware, and as an example simple NTB client.
@@ -147,7 +154,8 @@ Module Parameters:
* dyndbg - It is suggested to specify dyndbg=+p when loading this module, and
then to observe debugging output on the console.
-### NTB Tool Test Client (ntb\_tool)
+NTB Tool Test Client (ntb\_tool)
+--------------------------------
The Tool test client serves for debugging, primarily, ntb hardware and drivers.
The Tool provides access through debugfs for reading, setting, and clearing the
@@ -157,48 +165,60 @@ The Tool does not currently have any module parameters.
Debugfs Files:
-* *debugfs*/ntb\_tool/*hw*/ - A directory in debugfs will be created for each
+* *debugfs*/ntb\_tool/*hw*/
+ A directory in debugfs will be created for each
NTB device probed by the tool. This directory is shortened to *hw*
below.
-* *hw*/db - This file is used to read, set, and clear the local doorbell. Not
+* *hw*/db
+ This file is used to read, set, and clear the local doorbell. Not
all operations may be supported by all hardware. To read the doorbell,
read the file. To set the doorbell, write `s` followed by the bits to
set (eg: `echo 's 0x0101' > db`). To clear the doorbell, write `c`
followed by the bits to clear.
-* *hw*/mask - This file is used to read, set, and clear the local doorbell mask.
+* *hw*/mask
+ This file is used to read, set, and clear the local doorbell mask.
See *db* for details.
-* *hw*/peer\_db - This file is used to read, set, and clear the peer doorbell.
+* *hw*/peer\_db
+ This file is used to read, set, and clear the peer doorbell.
See *db* for details.
-* *hw*/peer\_mask - This file is used to read, set, and clear the peer doorbell
+* *hw*/peer\_mask
+ This file is used to read, set, and clear the peer doorbell
mask. See *db* for details.
-* *hw*/spad - This file is used to read and write local scratchpads. To read
+* *hw*/spad
+ This file is used to read and write local scratchpads. To read
the values of all scratchpads, read the file. To write values, write a
series of pairs of scratchpad number and value
(eg: `echo '4 0x123 7 0xabc' > spad`
# to set scratchpads `4` and `7` to `0x123` and `0xabc`, respectively).
-* *hw*/peer\_spad - This file is used to read and write peer scratchpads. See
+* *hw*/peer\_spad
+ This file is used to read and write peer scratchpads. See
*spad* for details.
-## NTB Hardware Drivers
+NTB Hardware Drivers
+====================
NTB hardware drivers should register devices with the NTB core driver. After
registering, clients probe and remove functions will be called.
-### NTB Intel Hardware Driver (ntb\_hw\_intel)
+NTB Intel Hardware Driver (ntb\_hw\_intel)
+------------------------------------------
The Intel hardware driver supports NTB on Xeon and Atom CPUs.
Module Parameters:
-* b2b\_mw\_idx - If the peer ntb is to be accessed via a memory window, then use
+* b2b\_mw\_idx
+ If the peer ntb is to be accessed via a memory window, then use
this memory window to access the peer ntb. A value of zero or positive
starts from the first mw idx, and a negative value starts from the last
mw idx. Both sides MUST set the same value here! The default value is
`-1`.
-* b2b\_mw\_share - If the peer ntb is to be accessed via a memory window, and if
+* b2b\_mw\_share
+ If the peer ntb is to be accessed via a memory window, and if
the memory window is large enough, still allow the client to use the
second half of the memory window for address translation to the peer.
-* xeon\_b2b\_usd\_bar2\_addr64 - If using B2B topology on Xeon hardware, use
+* xeon\_b2b\_usd\_bar2\_addr64
+ If using B2B topology on Xeon hardware, use
this 64 bit address on the bus between the NTB devices for the window
at BAR2, on the upstream side of the link.
* xeon\_b2b\_usd\_bar4\_addr64 - See *xeon\_b2b\_bar2\_addr64*.