Date:   Tue, 29 May 2018 11:15:18 -0500
From:   Alan Tull <atull@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Moritz Fischer <mdf@...nel.org>,
        linux-kernel <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 Fri, May 25, 2018 at 9:33 PM, Randy Dunlap <rdunlap@...radead.org> wrote:

Hi Randy,

Thanks for the reviews.  These are up on char-misc-next already, so
I'll send a patch to fix.

Alan

> 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

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