linux-kernel - Re: [PATCH v1 0/6] PolarFire SoC Auto Update Support

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Date:   Fri, 24 Feb 2023 08:28:24 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Xu Yilun <yilun.xu@...el.com>
CC:     Conor Dooley <conor@...nel.org>,
        Daire McNamara <daire.mcnamara@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Moritz Fischer <mdf@...nel.org>, Wu Hao <hao.wu@...el.com>,
        Tom Rix <trix@...hat.com>, <linux-riscv@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-fpga@...r.kernel.org>
Subject: Re: [PATCH v1 0/6] PolarFire SoC Auto Update Support

On Fri, Feb 24, 2023 at 03:57:09PM +0800, Xu Yilun wrote:
> On 2023-02-17 at 16:40:17 +0000, Conor Dooley wrote:

> > This patchset adds support for the "Auto Update" feature on PolarFire
> > SoC that allows for writing an FPGA bistream to the SPI flash connected
> > to the system controller.
> 
> I haven't fully checked the patches yet, just some quick comments:
> 
> Since this feature is just to R/W the flash, and would not affect the
> runtime FPGA region, I don't think an FPGA manager is actually needed.
> Why not just use the MTD uAPI? There is a set of exsiting MTD uAPI &
> MTD tool if I remember correctly.

A lack of interest in opening up the system controller to userspace!
You're right in that the writing of the image can be done that way, and
while I was testing I used the userspace bits of mtd along the way - but
for validating that the image we are writing we rely on the system
controller.
I'm really not interested in exposing the system controller's
functionality, especially the bitstream manipulation parts, to userspace
due to the risk of input validation bugs, so at least that side of
things should remain in the kernel.
I suppose I could implement something custom in drivers/soc that does
the validation only, and push the rest out to userspace. Just seemed
fitting to do the whole lot in drivers/fpga.

Cheers,
Conor.

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