linux-kernel - Re: [PATCH 12/14] documentation: fpga: move fpga-region.txt to driver-api

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Date:   Fri, 25 May 2018 19:33:37 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Alan Tull <atull@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Moritz Fischer <mdf@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-fpga@...r.kernel.org
Subject: Re: [PATCH 12/14] documentation: fpga: move fpga-region.txt to
 driver-api

On 05/16/2018 04:50 PM, Alan Tull wrote:
> Move Documentation/fpga/fpga-region.txt to
> driver-api/fpga/fpga-region.rst.  Including:
>  - Add it to driver-api/fpga/index.rst
>  - Formatting changes to build cleanly as ReST documentation
>  - Some rewrites for better flow as a ReST doc such as moving
>    API reference to the end of the doc
>  - Rewrite API reference section to refer to kernel-doc
>    documentation in fpga-region.c driver code
> 
> Signed-off-by: Alan Tull <atull@...nel.org>
> ---
>  Documentation/driver-api/fpga/fpga-region.rst | 102 ++++++++++++++++++++++++++
>  Documentation/driver-api/fpga/index.rst       |   1 +
>  Documentation/fpga/fpga-region.txt            |  94 ------------------------
>  3 files changed, 103 insertions(+), 94 deletions(-)
>  create mode 100644 Documentation/driver-api/fpga/fpga-region.rst
>  delete mode 100644 Documentation/fpga/fpga-region.txt
> 
> diff --git a/Documentation/driver-api/fpga/fpga-region.rst b/Documentation/driver-api/fpga/fpga-region.rst
> new file mode 100644
> index 0000000..f89e4a3
> --- /dev/null
> +++ b/Documentation/driver-api/fpga/fpga-region.rst
> @@ -0,0 +1,102 @@
> +FPGA Region
> +===========
> +
> +Overview
> +--------
> +
> +This document is meant to be an brief overview of the FPGA region API usage.  A

                                a brief overview

> +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 if for partial

                                                           is for

> +   reconfiguration.
> +
> +How to program a FPGA using a region

                  an FPGA

> +------------------------------------
> +
> +First, allocate the info struct::
> +
> +	info = fpga_image_info_alloc(dev);
> +	if (!info)
> +		return -ENOMEM;
> +
> +Set flags as needed, i.e.::
> +
> +	info->flags |= FPGA_MGR_PARTIAL_RECONFIG;
> +
> +Point to your FPGA image, such as::
> +
> +	info->sgt = &sgt;
> +
> +Add info to region and do the programming::
> +
> +	region->info = info;
> +	ret = fpga_region_program_fpga(region);
> +
> +:c:func:`fpga_region_program_fpga()` operates on info passed in the
> +fpga_image_info (region->info).  This function will attempt to:
> +
> + * lock the region's mutex
> + * lock the region's FPGA manager
> + * build a list of FPGA bridges if a method has been specified to do so
> + * disable the bridges
> + * program the FPGA
> + * re-enable the bridges
> + * release the locks
> +
> +Then you will want to enumerate whatever hardware has appeared in the FPGA.
> +
> +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 program a FGPA
> +---------------------
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> +   :functions: fpga_region_program_fpga
> +
> +API to add a new FPGA region
> +----------------------------
> +
> +.. kernel-doc:: include/linux/fpga/fpga-region.h
> +   :functions: fpga_region
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> +   :functions: fpga_region_create
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> +   :functions: fpga_region_free
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> +   :functions: fpga_region_register
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> +   :functions: fpga_region_unregister


-- 
~Randy