linux-kernel - Re: [PATCH v1] spi: fix client driver breakages when using GPIO descriptors

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Message-ID: <9c7aee21-0d08-9092-acdd-93477ed17dba@arm.com>
Date:   Wed, 25 Nov 2020 09:19:15 +0000
From:   Grant Likely <grant.likely@....com>
To:     Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Sven Van Asbroeck <thesven73@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Simon Han <z.han@...bus.com>, Lukas Wunner <lukas@...ner.de>,
        linux-spi <linux-spi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        nd <nd@....com>
Subject: Re: [PATCH v1] spi: fix client driver breakages when using GPIO
 descriptors



On 18/11/2020 11:40, Mark Brown wrote:
> On Wed, Nov 18, 2020 at 02:03:41AM +0100, Linus Walleij wrote:
>> On Mon, Nov 16, 2020 at 10:06 PM Mark Brown <broonie@...nel.org> wrote:
> 
>>> I think the main push in the other direction has always been people who
>>> want to not have to write a driver at all and put absolutely everything
>>> into DT which has scaling issues :/
> 
>> What I can't understand is what gave them that idea.
> 
>> This thing looks like a dream to these people for example:
>> https://gist.github.com/Minecrell/56c2b20118ba00a9723f0785301bc5ec#file-dsi_panel_s6e88a0_ams452ef01_qhd_octa_video-dtsi
>> And it looks like a nightmare to me.
> 
>> (There is even a tool to convert this description into a proper display
>> driver now.)
> 
>> It just seems to be one of those golden hammer things: everything
>> start to look like nails.
> 
> What people think they were sold was the idea that they shouldn't have
> to write driver code or upstream things, something with more AML like
> capabilities (not realising that AML works partly because ACPI hugely
> constrains system design).

And is also untrue. AML only provides an API abstraction for a specific 
power management model. All the actual driving of the device still 
requires driver code and requires reading devices-specific properties 
out of the ACPI node.

g.