1FPGA Region
2===========
3
4Overview
5--------
6
7This document is meant to be a brief overview of the FPGA region API usage.  A
8more conceptual look at regions can be found in the Device Tree binding
9document [#f1]_.
10
11For the purposes of this API document, let's just say that a region associates
12an FPGA Manager and a bridge (or bridges) with a reprogrammable region of an
13FPGA or the whole FPGA.  The API provides a way to register a region and to
14program a region.
15
16Currently the only layer above fpga-region.c in the kernel is the Device Tree
17support (of-fpga-region.c) described in [#f1]_.  The DT support layer uses regions
18to program the FPGA and then DT to handle enumeration.  The common region code
19is intended to be used by other schemes that have other ways of accomplishing
20enumeration after programming.
21
22An fpga-region can be set up to know the following things:
23
24 * which FPGA manager to use to do the programming
25
26 * which bridges to disable before programming and enable afterwards.
27
28Additional info needed to program the FPGA image is passed in the struct
29fpga_image_info including:
30
31 * pointers to the image as either a scatter-gather buffer, a contiguous
32   buffer, or the name of firmware file
33
34 * flags indicating specifics such as whether the image is for partial
35   reconfiguration.
36
37How to add a new FPGA region
38----------------------------
39
40An example of usage can be seen in the probe function of [#f2]_.
41
42.. [#f1] ../devicetree/bindings/fpga/fpga-region.txt
43.. [#f2] ../../drivers/fpga/of-fpga-region.c
44
45API to add a new FPGA region
46----------------------------
47
48* struct fpga_region - The FPGA region struct
49* struct fpga_region_info - Parameter structure for __fpga_region_register_full()
50* __fpga_region_register_full() -  Create and register an FPGA region using the
51  fpga_region_info structure to provide the full flexibility of options
52* __fpga_region_register() -  Create and register an FPGA region using standard
53  arguments
54* fpga_region_unregister() -  Unregister an FPGA region
55
56Helper macros ``fpga_region_register()`` and ``fpga_region_register_full()``
57automatically set the module that registers the FPGA region as the owner.
58
59The FPGA region's probe function will need to get a reference to the FPGA
60Manager it will be using to do the programming.  This usually would happen
61during the region's probe function.
62
63* fpga_mgr_get() - Get a reference to an FPGA manager, raise ref count
64* of_fpga_mgr_get() -  Get a reference to an FPGA manager, raise ref count,
65  given a device node.
66* fpga_mgr_put() - Put an FPGA manager
67
68The FPGA region will need to specify which bridges to control while programming
69the FPGA.  The region driver can build a list of bridges during probe time
70(:c:expr:`fpga_region->bridge_list`) or it can have a function that creates
71the list of bridges to program just before programming
72(:c:expr:`fpga_region->get_bridges`).  The FPGA bridge framework supplies the
73following APIs to handle building or tearing down that list.
74
75* fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a
76  list
77* of_fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a
78  list, given a device node
79* fpga_bridges_put() - Given a list of bridges, put them
80
81.. kernel-doc:: include/linux/fpga/fpga-region.h
82   :functions: fpga_region
83
84.. kernel-doc:: include/linux/fpga/fpga-region.h
85   :functions: fpga_region_info
86
87.. kernel-doc:: drivers/fpga/fpga-region.c
88   :functions: __fpga_region_register_full
89
90.. kernel-doc:: drivers/fpga/fpga-region.c
91   :functions: __fpga_region_register
92
93.. kernel-doc:: drivers/fpga/fpga-region.c
94   :functions: fpga_region_unregister
95
96.. kernel-doc:: drivers/fpga/fpga-mgr.c
97   :functions: fpga_mgr_get
98
99.. kernel-doc:: drivers/fpga/fpga-mgr.c
100   :functions: of_fpga_mgr_get
101
102.. kernel-doc:: drivers/fpga/fpga-mgr.c
103   :functions: fpga_mgr_put
104
105.. kernel-doc:: drivers/fpga/fpga-bridge.c
106   :functions: fpga_bridge_get_to_list
107
108.. kernel-doc:: drivers/fpga/fpga-bridge.c
109   :functions: of_fpga_bridge_get_to_list
110
111.. kernel-doc:: drivers/fpga/fpga-bridge.c
112   :functions: fpga_bridges_put
113