linux-kernel - Re: [PATCH] pinctrl: generic: Avoid several implicit enum conversions

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Message-ID: <CACRpkdadODxsuae7uhwcfBBMQ-eZ8bvnV71fhDCuudbJEbhhYA@mail.gmail.com>
Date:   Tue, 25 Sep 2018 12:58:16 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     natechancellor@...il.com
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        ndesaulniers@...gle.com
Subject: Re: [PATCH] pinctrl: generic: Avoid several implicit enum conversions

On Tue, Sep 25, 2018 at 8:19 AM Nathan Chancellor
<natechancellor@...il.com> wrote:

> Clang warns when one enumerated type is implicitly converted to another,
> which happens several times in the pinctrl drivers for a few reasons:
>
> * The PCONFDUMP macro, which sets the param member in pin_config_item.
> * The pinconf_generic_params structure, which is used by drivers to
>   configure their bindings, which has a param member like pin_config_item.
> * The pinconf_to_config_packed, which takes either the generic enum
>   pin_config_param or a specialized one.
>
> Drivers are allowed to extend this enumerated type because of the gap
> betweem PIN_CONFIG_END and PIN_CONFIG_MAX. Make it clear to Clang that
> this is allowed by changing param's type in all of these instances to
> int so no conversion needs to happen.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/138
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

I'm not superhappy about this because that enum is great for readability,
even if the static syntax checker is unhappy.

If we can't have an enum here I would argue that we can just as well
remove the enum altogether and just use #define for the config
parameters, would you agree?

Yours,
Linus Walleij