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Subject: Re: [PATCH v3 3/3] Documentation: fpga: dfl: Add description for DFL
 UIO support
To:     Xu Yilun <yilun.xu@intel.com>, mdf@kernel.org,
        linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     gregkh@linuxfoundation.org, lgoncalv@redhat.com, hao.wu@intel.com
References: <1608183881-18692-1-git-send-email-yilun.xu@intel.com>
 <1608183881-18692-4-git-send-email-yilun.xu@intel.com>
From:   Tom Rix <trix@redhat.com>
Message-ID: <994de3b8-0374-40d1-2644-5604742a264e@redhat.com>
Date:   Thu, 17 Dec 2020 05:26:29 -0800
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On 12/16/20 9:44 PM, Xu Yilun wrote:
> This patch adds description for UIO support for dfl devices on DFL
> bus.

Thanks for the changes.

Reviewed-by: Tom Rix <trix@redhat.com>

> Signed-off-by: Xu Yilun <yilun.xu@intel.com>
> ---
> v2: no doc in v1, add it for v2.
> v3: some documentation fixes.
> ---
>  Documentation/fpga/dfl.rst | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> index 0404fe6..b298ad9 100644
> --- a/Documentation/fpga/dfl.rst
> +++ b/Documentation/fpga/dfl.rst
> @@ -7,6 +7,7 @@ Authors:
>  - Enno Luebbers <enno.luebbers@intel.com>
>  - Xiao Guangrong <guangrong.xiao@linux.intel.com>
>  - Wu Hao <hao.wu@intel.com>
> +- Xu Yilun <yilun.xu@intel.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 +503,32 @@ 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
> +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 this feature.
> +
> +The DFL UIO driver has a special matching algorithem. It will match any DFL
> +device which could not be handled by other DFL drivers. In this way, it will
> +not impact the functionality of the features which are already supported by the
> +system.
> +
> +
>  Open discussion
>  ===============
>  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration