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authorRodrigo Vivi <[email protected]>2018-07-23 09:13:12 -0700
committerRodrigo Vivi <[email protected]>2018-07-23 09:13:12 -0700
commitc74a7469f97c0f40b46e82ee979f9fb1bb6e847c (patch)
treef2690a1a916b73ef94657fbf0e0141ae57701825 /Documentation/driver-api/fpga/intro.rst
parent6f15a7de86c8cf2dc09fc9e6d07047efa40ef809 (diff)
parent500775074f88d9cf5416bed2ca19592812d62c41 (diff)
Merge drm/drm-next into drm-intel-next-queued
We need a backmerge to get DP_DPCD_REV_14 before we push other i915 changes to dinq that could break compilation. Signed-off-by: Rodrigo Vivi <[email protected]>
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+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.