linux-kernel - Re: [PATCH 1/2] x86: Remove led/gpio setup from pcengines platform driver

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Date:   Tue, 13 Oct 2020 22:46:09 +0100
From:   Ed W <lists@...dgooses.com>
To:     Hans de Goede <hdegoede@...hat.com>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        linux-kernel@...r.kernel.org
Cc:     fe@....tdt.de, "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH 1/2] x86: Remove led/gpio setup from pcengines platform
 driver

On 13/10/2020 09:48, Hans de Goede wrote:

> On 10/12/20 9:39 PM, Enrico Weigelt, metux IT consult wrote:
>> On 22.09.20 00:17, Ed W wrote:
>>> Hi, I've been adding support for the PC Engines APU5 board, which is a variant of the APU 2-4
>>> boards
>>> with some nice features. The current platform driver for pcengines boards has some redundant
>>> features with regards to recent bios/firmware packages for the board as they now set the ACPI
>>> tables
>>> to indicate GPIOs for keys and leds.
>>
>> NAK. Breaks existing userlands in the field (literally field), forcing
>> users to fw upgrade is not an option (field roll would be realy expensive).
>
> Thank you Enrico, I was wondering the same (what about userspace breakage)
> when I was looking at this patch. It is good to have confirmation that
> userspace breakage is a real issue here.

This isn't the whole story.

The original naming was board specific. Then Enrico (not unreasonably - I actually prefer his
naming) changed the naming to be non board specific. Then within 2 months PC Engines introduced ACPI
based config using the old names.

So if we are holding "userspace breakage" as the gold standard, then the original (also the current)
names have actually been around longest and likely cause the least userspace breakage.

Also, some other pieces of this module have already been removed (SIM Swap), so there is an existing
precedent for "userspace breakage" and trimming down this platform driver.

In big picture terms, changing the name of the LED device doesn't seem a huge concern to me... A
udev rule can setup compatibility forwards/backwards quite trivially I think?

Kind regards

Ed W