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Date: Tue, 14 Aug 2018 19:40:19 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Alan Tull <atull@...nel.org>, Moritz Fischer <mdf@...nel.org>,
Jonathan Corbet <corbet@....net>
Cc: linux-kernel@...r.kernel.org, linux-fpga@...r.kernel.org,
linux-doc@...r.kernel.org
Subject: Re: [PATCH 8/8] docs: fpga: document programming fpgas using regions
On 08/14/2018 12:15 PM, Alan Tull wrote:
> Clarify the intention that interfaces and upper layers use
> regions rather than managers directly.
>
> Rearrange API documentation to better group the API functions
> used to create FPGA mgr/bridge/regions and the API used for
> programming FPGAs.
>
> Signed-off-by: Alan Tull <atull@...nel.org>
> ---
> Documentation/driver-api/fpga/fpga-bridge.rst | 38 ++-----
> Documentation/driver-api/fpga/fpga-mgr.rst | 117 ++-------------------
> Documentation/driver-api/fpga/fpga-programming.rst | 103 ++++++++++++++++++
> Documentation/driver-api/fpga/fpga-region.rst | 92 ++++++++--------
> Documentation/driver-api/fpga/index.rst | 2 +
> 5 files changed, 166 insertions(+), 186 deletions(-)
> create mode 100644 Documentation/driver-api/fpga/fpga-programming.rst
>
Hi,
A few comments below...
> diff --git a/Documentation/driver-api/fpga/fpga-programming.rst b/Documentation/driver-api/fpga/fpga-programming.rst
> new file mode 100644
> index 0000000..cc34d17
> --- /dev/null
> +++ b/Documentation/driver-api/fpga/fpga-programming.rst
> @@ -0,0 +1,103 @@
> +In-kernel API for FPGA Programming
> +==================================
> +
> +Overview
> +--------
> +
> +The in-kernel API for FPGA programming is a combination of APIs from
> +FPGA manager, bridge, and regions. The actual function used to
> +trigger FPGA programming is :c:func:`fpga_region_program_fpga()`.
> +
> +:c:func:`fpga_region_program_fpga()` uses functionality supplied by
> +the FPGA manager and bridges. It will:
> +
> + * lock the region's mutex
> + * lock the mutex of 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 using info passed in :c:member:`fpga_region->info`.
> + * re-enable the bridges
> + * release the locks
> +
> +The struct fpga_image_info specifies what FPGA image to program. It is allocated/freed by :c:func:`fpga_image_info_alloc()` and freed with :c:func:`fpga_image_info_free()`
> +
> +How to program an FPGA using a region
> +-------------------------------------
> +
> +When the FPGA region driver probed, it was given a pointer to a FPGA manager
to an FPGA
> +driver so it knows which manager to use. The region also either has a list of
> +bridges to control during programming or it has a pointer to a function that
> +will generate that list. Here's some sample code of what to do next::
> +
> + #include <linux/fpga/fpga-mgr.h>
> + #include <linux/fpga/fpga-region.h>
> +
> + struct fpga_image_info *info;
> + int ret;
> +
> + /*
> + * First, alloc the struct with information about the FPGA image to
> + * program.
> + */
> + info = fpga_image_info_alloc(dev);
> + if (!info)
> + return -ENOMEM;
> +
> + /* Set flags as needed, such as: */
> + info->flags = FPGA_MGR_PARTIAL_RECONFIG;
> +
> + /*
> + * Indicate where the FPGA image is. This is pseudo-code; you're
> + * going to use one of these three.
> + */
> + if (image is in a scatter gather table) {
> +
> + info->sgt = [your scatter gather table]
> +
> + } else if (image is in a buffer) {
> +
> + info->buf = [your image buffer]
> + info->count = [image buffer size]
> +
> + } else if (image is in a firmware file) {
> +
> + info->firmware_name = devm_kstrdup(dev, firmware_name,
> + GFP_KERNEL);
> +
> + }
> +
> + /* Add info to region and do the programming */
> + region->info = info;
> + ret = fpga_region_program_fpga(region);
> + if (ret)
> + return ret;
> +
always deallocate and then do:
if (ret)
return ret;
?
> + /* Deallocate the image info if you're done with it */
> + fpga_image_info_free(info);
> +
> + /* Now enumerate whatever hardware has appeared in the FPGA. */
> +
> +API for programming an FPGA
> +---------------------------
> +
> +* :c:func:`fpga_region_program_fpga` — Program a FPGA
> +* :c:type:`fpga_image_info` — Specifies what FPGA image to program
> +* :c:func:`fpga_image_info_alloc()` — Allocate a FPGA image info struct
> +* :c:func:`fpga_image_info_free()` — Free a FPGA image info struct
> +
> +.. kernel-doc:: drivers/fpga/fpga-region.c
> + :functions: fpga_region_program_fpga
> +
> +FPGA Manager flags
> +
> +.. kernel-doc:: include/linux/fpga/fpga-mgr.h
> + :doc: FPGA Manager flags
> +
> +.. kernel-doc:: include/linux/fpga/fpga-mgr.h
> + :functions: fpga_image_info
> +
> +.. kernel-doc:: drivers/fpga/fpga-mgr.c
> + :functions: fpga_image_info_alloc
> +
> +.. kernel-doc:: drivers/fpga/fpga-mgr.c
> + :functions: fpga_image_info_free
[snip]
> API to add a new FPGA region
> ----------------------------
>
> +* struct :c:type:`fpga_region` — The FPGA region struct
> +* :c:func:`devm_fpga_region_create` — Allocate and init a region struct
> +* :c:func:`fpga_region_register` — Register a FPGA region
an FPGA
> +* :c:func:`fpga_region_unregister` — Unregister a FPGA region
an FPGA
> +
> +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.
> +
> +* :c:func:`fpga_mgr_get` — Get a reference to a FPGA manager, raise ref count
an FPGA
> +* :c:func:`of_fpga_mgr_get` — Get a reference to a FPGA manager, raise ref count,
an FPGA
> + given a device node.
> +* :c:func:`fpga_mgr_put` — Put a FPGA manager
an FPGA
> +
> +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:member:`fpga_region->bridge_list`) or it can have a function that creates
> +the list of bridges to program just before programming
> +(:c:member:`fpga_region->get_bridges`). The FPGA bridge framework supplies the
> +following APIs to handle building or tearing down that list.
> +
> +* :c:func:`fpga_bridge_get_to_list` — Get a ref of a FPGA bridge, add it to a
> + list
> +* :c:func:`of_fpga_bridge_get_to_list` — Get a ref of a FPGA bridge, add it to a
> + list, given a device node
> +* :c:func:`fpga_bridges_put` — Given a list of bridges, put them
> +
> .. kernel-doc:: include/linux/fpga/fpga-region.h
> :functions: fpga_region
>
--
~Randy
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