linux-kernel - Re: [PATCH v2 6/6] pinctrl: intel: Enumerate PWM device when community has a capabilitty

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACRpkda6uDOEXybduFbTe0yXzLMaQ8x0UORZAH-U0SOTWHkF-Q@mail.gmail.com>
Date:   Wed, 9 Nov 2022 11:08:04 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH v2 6/6] pinctrl: intel: Enumerate PWM device when
 community has a capabilitty

On Wed, Nov 9, 2022 at 10:56 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Wed, Nov 09, 2022 at 10:08:51AM +0100, Linus Walleij wrote:

> > I guess I can be convinced that this hack is the lesser evil :D
> >
> > What is it in the platform that makes this kind of hacks necessary?
>
> The PWM capability is discoverable by the looking for it in the pin
> control IP MMIO, it's not a separate device, but a sibling (child?)
> of the pin control, that's not a separate entity.

OK I get it.

> Moreover, not every pin control _community_ has that capability (capabilities
> are on the Community level and depends on ACPI representation of the
> communities themself - single device or device per community - the PWM may or
> may not be easily attached.

OK I think I understand it a bit, if ACPI thinks about the PWM
as "some feature of the community" then that is how it is, we have
this bad fit between device tree and Linux internals at times as well,
then spawning a device from another one is the way to go, we need
to consider the option that it is Linux that is weird at times, not the
HW description.

> What you are proposing is to invent at least two additional properties or so
> for the pin control device description and then to support old platforms,
> create a board file somewhere else, which will go through all pin control
> devices, checks the capabilities, then embeds the properties via properties
> (Either embedded into DSDT, if done in BIOS, or swnodes).
>
> Do I get you right?
>
> If so, in my opinion it's way more ugly and overkill that the current
> approach.

No I just wanted to understand things better. This small hack in the
pin controller is way better than a bigger and widespread hack
somewhere else.

> That said, I agree that this looks not nice, but that's all what
> Mika and me can come up with to make all this as little ugly and
> intrusive as possible.

I can live with it, rough consensus and running code.
Acked-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij