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Diffstat (limited to 'Documentation/driver-api/fpga/fpga-region.rst')
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diff --git a/Documentation/driver-api/fpga/fpga-region.rst b/Documentation/driver-api/fpga/fpga-region.rst new file mode 100644 index 000000000..dc55d60a0 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-region.rst @@ -0,0 +1,109 @@ +FPGA Region +=========== + +Overview +-------- + +This document is meant to be a brief overview of the FPGA region API usage. A +more conceptual look at regions can be found in the Device Tree binding +document [#f1]_. + +For the purposes of this API document, let's just say that a region associates +an FPGA Manager and a bridge (or bridges) with a reprogrammable region of an +FPGA or the whole FPGA. The API provides a way to register a region and to +program a region. + +Currently the only layer above fpga-region.c in the kernel is the Device Tree +support (of-fpga-region.c) described in [#f1]_. The DT support layer uses regions +to program the FPGA and then DT to handle enumeration. The common region code +is intended to be used by other schemes that have other ways of accomplishing +enumeration after programming. + +An fpga-region can be set up to know the following things: + + * which FPGA manager to use to do the programming + + * which bridges to disable before programming and enable afterwards. + +Additional info needed to program the FPGA image is passed in the struct +fpga_image_info including: + + * pointers to the image as either a scatter-gather buffer, a contiguous + buffer, or the name of firmware file + + * flags indicating specifics such as whether the image is for partial + reconfiguration. + +How to add a new FPGA region +---------------------------- + +An example of usage can be seen in the probe function of [#f2]_. + +.. [#f1] ../devicetree/bindings/fpga/fpga-region.txt +.. [#f2] ../../drivers/fpga/of-fpga-region.c + +API to add a new FPGA region +---------------------------- + +* struct fpga_region - The FPGA region struct +* struct fpga_region_info - Parameter structure for fpga_region_register_full() +* fpga_region_register_full() - Create and register an FPGA region using the + fpga_region_info structure to provide the full flexibility of options +* fpga_region_register() - Create and register an FPGA region using standard + arguments +* fpga_region_unregister() - Unregister an FPGA region + +The FPGA region's probe function will need to get a reference to the FPGA +Manager it will be using to do the programming. This usually would happen +during the region's probe function. + +* fpga_mgr_get() - Get a reference to an FPGA manager, raise ref count +* of_fpga_mgr_get() - Get a reference to an FPGA manager, raise ref count, + given a device node. +* fpga_mgr_put() - Put an FPGA manager + +The FPGA region will need to specify which bridges to control while programming +the FPGA. The region driver can build a list of bridges during probe time +(:c:expr:`fpga_region->bridge_list`) or it can have a function that creates +the list of bridges to program just before programming +(:c:expr:`fpga_region->get_bridges`). The FPGA bridge framework supplies the +following APIs to handle building or tearing down that list. + +* fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a + list +* of_fpga_bridge_get_to_list() - Get a ref of an FPGA bridge, add it to a + list, given a device node +* fpga_bridges_put() - Given a list of bridges, put them + +.. kernel-doc:: include/linux/fpga/fpga-region.h + :functions: fpga_region + +.. kernel-doc:: include/linux/fpga/fpga-region.h + :functions: fpga_region_info + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_register_full + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_register + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_unregister + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_get + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: of_fpga_mgr_get + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_mgr_put + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridge_get_to_list + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: of_fpga_bridge_get_to_list + +.. kernel-doc:: drivers/fpga/fpga-bridge.c + :functions: fpga_bridges_put |