linux-kernel - Re: [PATCH v5 2/2] Documentation: fpga: dfl: Add description for DFL UIO support

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Date:   Mon, 4 Jan 2021 09:19:24 -0800
From:   Russ Weight <russell.h.weight@...el.com>
To:     Xu Yilun <yilun.xu@...el.com>, mdf@...nel.org,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, trix@...hat.com, lgoncalv@...hat.com,
        hao.wu@...el.com
Subject: Re: [PATCH v5 2/2] Documentation: fpga: dfl: Add description for DFL
 UIO support



On 1/1/21 7:13 PM, Xu Yilun wrote:
> This patch adds description for UIO support for dfl devices on DFL
> bus.
>
> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> ---
> v2: no doc in v1, add it for v2.
> v3: some documentation fixes.
> v4: documentation change since the driver matching is changed.
> v5: no change.
> ---
>  Documentation/fpga/dfl.rst | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> index 0404fe6..b8497f3 100644
> --- a/Documentation/fpga/dfl.rst
> +++ b/Documentation/fpga/dfl.rst
> @@ -7,6 +7,7 @@ Authors:
>  - Enno Luebbers <enno.luebbers@...el.com>
>  - Xiao Guangrong <guangrong.xiao@...ux.intel.com>
>  - Wu Hao <hao.wu@...el.com>
> +- Xu Yilun <yilun.xu@...el.com>
>  
>  The Device Feature List (DFL) FPGA framework (and drivers according to
>  this framework) hides the very details of low layer hardwares and provides
> @@ -502,6 +503,29 @@ FME Partial Reconfiguration Sub Feature driver (see drivers/fpga/dfl-fme-pr.c)
>  could be a reference.
>  
>  
> +UIO support for DFL devices
> +===========================
> +The purpose of an FPGA is to be reprogrammed with newly developed hardware
> +components. New hardware can instantiate a new private feature in the DFL, and
> +then get a DFL device in their system. In some cases users may need a userspace
> +driver for the DFL device:
> +
> +* Users may need to run some diagnostic test for their hardwares.
> +* Users may prototype the kernel driver in user space.
> +* Some hardware is designed for specific purposes and does not fit into one of
> +  the standard kernel subsystems.
> +
> +This requires the direct access to the MMIO space and interrupt handling in
This may be better stated as:

"This requires direct access to MMIO space and interrupt handling from userspace."

- Russ

> +userspace. The dfl-uio-pdev module exposes the UIO device interfaces for this
> +purpose. It adds the uio_pdrv_genirq platform device with the resources of
> +the DFL feature, and lets the generic UIO platform device driver provide UIO
> +support to userspace.
> +
> +FPGA_DFL_UIO_PDEV should be selected to enable the dfl-uio-pdev module driver.
> +To support a new DFL feature been directly accessed via UIO, its feature id
> +should be added to the driver's id_table.
> +
> +
>  Open discussion
>  ===============
>  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration