linux-kernel - Re: [PATCH v5 0/2] UIO support for dfl devices

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Message-ID: <X/tcdB0hwDLog1TW@archbook>
Date:   Sun, 10 Jan 2021 11:58:44 -0800
From:   Moritz Fischer <mdf@...nel.org>
To:     Xu Yilun <yilun.xu@...el.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        trix@...hat.com, lgoncalv@...hat.com, hao.wu@...el.com
Subject: Re: [PATCH v5 0/2] UIO support for dfl devices

Hi Xu,

On Sat, Jan 02, 2021 at 11:13:00AM +0800, Xu Yilun wrote:
> This patchset supports some dfl device drivers written in userspace.
> 
> In the patchset v1, the "driver_override" interface should be used to bind
> the DFL UIO driver to DFL devices. But there is concern that the
> "driver_override" interface is not OK itself.
> 
> In v2, we use a new matching algorithem. The "driver_override" interface
> is abandoned, the DFL UIO driver matches any DFL device which could not be
> handled by other DFL drivers. So the DFL UIO driver could be used for new
> DFL devices which are not supported by kernel. The concern is the UIO may
> not be suitable as a default/generic driver for all dfl features, such as
> features with multiple interrupts.
> 
> In v4, we specify each matching device in the id_table of the UIO driver,
> just the same as other dfl drivers do. Now the UIO driver supports Ether
> Group feature. To support more DFL features, their feature ids should be
> added to the driver's id_table.

I think this is what you want, yes. Instead of doing a driver override
or such, add devices that should always be bound to UIO to a device id
table. For those you temporarily want to bind, make sure you can unbind
them and use 'new_id' or 'bind' in sysfs, similar to what sysfs does.

> 
> 
> Main changes from v1:
> - switch to the new matching algorithem. It matches DFL devices which could
>   not be handled by other DFL drivers.
> - refacor the code about device resources filling.
> - add the documentation.
> 
> Main changes from v2:
> - split the match ops changes in dfl.c to an independent patch.
> - move the declarations needed for dfl-uio-pdev from include/linux/dfl.h
>   to driver/fpga/dfl.h
> - some minor fixes.
> 
> Main changes from v3:
> - switch to specifying each matching device in the driver's id_table.
> - refactor the irq handling code.
> 
> Main changes from v4:
> - refactor the irq handling code.
> 
> Xu Yilun (2):
>   fpga: dfl: add the userspace I/O device support for DFL devices
>   Documentation: fpga: dfl: Add description for DFL UIO support
> 
>  Documentation/fpga/dfl.rst  | 24 ++++++++++++
>  drivers/fpga/Kconfig        | 10 +++++
>  drivers/fpga/Makefile       |  1 +
>  drivers/fpga/dfl-uio-pdev.c | 91 +++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 126 insertions(+)
>  create mode 100644 drivers/fpga/dfl-uio-pdev.c
> 
> -- 
> 2.7.4
> 

- Moritz