Documentation: fpga: move fpga overview to driver-api
Start of moving Documentation/fpga/*.txt to driver-api, including:
- Add new directory driver-api/fpga
- Add new file driver-api/fpga/index.rst
- Add driver-api/fpga to driver-api/index.rst
- Move Documentation/fpga/overview.txt to driver-api/fpga/intro.rst
- Formatting and rewrites so that intro.rst will build cleanly
and form a good introduction to the rest of the docs to be added.
Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/driver-api/fpga/index.rst b/Documentation/driver-api/fpga/index.rst
new file mode 100644
index 0000000..71e568a
--- /dev/null
+++ b/Documentation/driver-api/fpga/index.rst
@@ -0,0 +1,10 @@
+==============
+FPGA Subsystem
+==============
+
+:Author: Alan Tull
+
+.. toctree::
+ :maxdepth: 2
+
+ intro
diff --git a/Documentation/driver-api/fpga/intro.rst b/Documentation/driver-api/fpga/intro.rst
new file mode 100644
index 0000000..51cd81d
--- /dev/null
+++ b/Documentation/driver-api/fpga/intro.rst
@@ -0,0 +1,54 @@
+Introduction
+============
+
+The FPGA subsystem supports reprogramming FPGAs dynamically under
+Linux. Some of the core intentions of the FPGA subsystems are:
+
+* The FPGA subsystem is vendor agnostic.
+
+* The FPGA subsystem separates upper layers (userspace interfaces and
+ enumeration) from lower layers that know how to program a specific
+ FPGA.
+
+* Code should not be shared between upper and lower layers. This
+ should go without saying. If that seems necessary, there's probably
+ framework functionality that that can be added that will benefit
+ other users. Write the linux-fpga mailing list and maintainers and
+ seek out a solution that expands the framework for broad reuse.
+
+* Generally, when adding code, think of the future. Plan for re-use.
+
+The framework in the kernel is divided into:
+
+FPGA Manager
+------------
+
+If you are adding a new FPGA or a new method of programming a FPGA,
+this is the subsystem for you. Low level FPGA manager drivers contain
+the knowledge of how to program a specific device. This subsystem
+includes the framework in fpga-mgr.c and the low level drivers that
+are registered with it.
+
+FPGA Bridge
+-----------
+
+FPGA Bridges prevent spurious signals from going out of a FPGA or a
+region of a FPGA during programming. They are disabled before
+programming begins and re-enabled afterwards. An FPGA bridge may be
+actual hard hardware that gates a bus to a cpu or a soft ("freeze")
+bridge in FPGA fabric that surrounds a partial reconfiguration region
+of an FPGA. This subsystem includes fpga-bridge.c and the low level
+drivers that are registered with it.
+
+FPGA Region
+-----------
+
+If you are adding a new interface to the FPGA framework, add it on top
+of a FPGA region to allow the most reuse of your interface.
+
+The FPGA Region framework (fpga-region.c) associates managers and
+bridges as reconfigurable regions. A region may refer to the whole
+FPGA in full reconfiguration or to a partial reconfiguration region.
+
+The Device Tree FPGA Region support (of-fpga-region.c) handles
+reprogramming FPGAs when device tree overlays are applied.
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index 6d8352c..ed40ec0 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -49,6 +49,7 @@
dmaengine/index
slimbus
soundwire/index
+ fpga/index
.. only:: subproject and html
diff --git a/Documentation/fpga/overview.txt b/Documentation/fpga/overview.txt
deleted file mode 100644
index 0f1236e..0000000
--- a/Documentation/fpga/overview.txt
+++ /dev/null
@@ -1,23 +0,0 @@
-Linux kernel FPGA support
-
-Alan Tull 2017
-
-The main point of this project has been to separate the out the upper layers
-that know when to reprogram a FPGA from the lower layers that know how to
-reprogram a specific FPGA device. The intention is to make this manufacturer
-agnostic, understanding that of course the FPGA images are very device specific
-themselves.
-
-The framework in the kernel includes:
-* low level FPGA manager drivers that know how to program a specific device
-* the fpga-mgr framework they are registered with
-* low level FPGA bridge drivers for hard/soft bridges which are intended to
- be disable during FPGA programming
-* the fpga-bridge framework they are registered with
-* the fpga-region framework which associates and controls managers and bridges
- as reconfigurable regions
-* the of-fpga-region support for reprogramming FPGAs when device tree overlays
- are applied.
-
-I would encourage you the user to add code that creates FPGA regions rather
-that trying to control managers and bridges separately.
