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In-Reply-To: <Y+JkArdW747OtMO9@black.fi.intel.com>
From:   Mauro Lima <mauro.lima@eclypsium.com>
Date:   Tue, 7 Feb 2023 17:44:06 -0300
Message-ID: <CAArk9MMC=xq3HetGG-F8OQk4J6=b5rNpoPfou0e5T8w4fpDFnQ@mail.gmail.com>
Subject: Re: [PATCH 1/1] spi: intel: Remove DANGEROUS tag from pci driver
To:     Mika Westerberg <mika.westerberg@linux.intel.com>
Cc:     Michael Walle <michael@walle.cc>, broonie@kernel.org,
        linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org
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Hi all,

On Tue, Feb 7, 2023 at 2:25 PM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> Hi,
>
> On Tue, Feb 07, 2023 at 03:11:26PM +0100, Michael Walle wrote:
> > Hi Mika,
> >
> > Am 2023-02-07 15:03, schrieb Mika Westerberg:
> > > On Tue, Feb 07, 2023 at 02:52:54PM +0100, Michael Walle wrote:
> > > > > Modern CPUs exposes this controller as PCI device that only uses
> > > > > hardware sequencing capabilities which is safer than software
> > > > > sequencing.
> > > > > Leave the platform driver as *DANGEROUS* and update help text since
> > > > > most of these controllers are using software sequencing.
> > > >
> > > > Out of curiosity, what is hardware sequencing? Maybe this should
> > > > be explained a bit more in the Kconfig help text. Looks like the
> > > > dangerous was there because you can update the bios and that
> > > > could eventually lead to a bricked mainboard. So hardware
> > > > sequencing helps there? how?
> > >
> > > Hardware sequencing means the controller exposes just a bunch of "high
> > > level" operations to the software.
> >
> > Ok, I figured it would have been something to do with the SPI driver
> > just supporting these high level ops. But even with that background
> > it was hard to connect that to the "hardware sequencing". The help
> > text should be somewhat understandable to the user/distro people/whoever,
> > right? So I'd suggest to explain that a bit more in detail, or don't
> > use the term hardware sequencing at all. I'm not sure.
>
> I agree it should be made more understandable for the distro folks. At
> least add some explanation why it is OK to select this.
I agree with this.
> Mauro, can you do that in the next version?
Sure thing.
> > > Such as read, write, erase and so on
> > > but does not allow running the actual "low level" SPI-NOR opcodes.
> > > Software sequencing on the other hand allows running pretty much any
> > > opcode and this is what caused problems for certain Lenovo laptops few
> > > years back that then resulted adding DANGEROUS to the Kconfig.
> >
> > That information should go into the commit message.
>
> +1
Sorry about this, still learning :)

Thanks all for your comments and time.