linux-kernel - Re: [PATCH v2 2/7] usb: typec: mux: Add CONFIG guards for functions

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Date:   Tue, 14 Jun 2022 10:27:04 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     heikki.krogerus@...ux.intel.com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        kernel test robot <lkp@...el.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Jonas Karlman <jonas@...boo.se>,
        swboyd@...omium.org, Pin-Yen Lin <treapking@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime@...no.tech>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Xin Ji <xji@...logixsemi.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robert Foss <robert.foss@...aro.org>,
        José Expósito <jose.exposito89@...il.com>
Subject: Re: [PATCH v2 2/7] usb: typec: mux: Add CONFIG guards for functions

Il 09/06/22 20:09, Prashant Malani ha scritto:
> There are some drivers that can use the Type C mux API, but don't have
> to. Introduce CONFIG guards for the mux functions so that drivers can
> include the header file and not run into compilation errors on systems
> which don't have CONFIG_TYPEC enabled. When CONFIG_TYPEC is not enabled,
> the Type C mux functions will be stub versions of the original calls.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
> 
> Changes since v1:
> - Added static inline to stub functions.
> - Updated function signature of stub functions from "struct typec_mux"
>    to "struct typec_mux_dev" in accordance with updates from commit
>    713fd49b430c ("usb: typec: mux: Introduce indirection")
> 
>   include/linux/usb/typec_mux.h | 38 +++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
> 
> diff --git a/include/linux/usb/typec_mux.h b/include/linux/usb/typec_mux.h
> index ee57781dcf28..9eda6146fd26 100644
> --- a/include/linux/usb/typec_mux.h
> +++ b/include/linux/usb/typec_mux.h
> @@ -58,6 +58,8 @@ struct typec_mux_desc {
>   	void *drvdata;
>   };
>   
> +#if IS_ENABLED(CONFIG_TYPEC) || IS_MODULE(CONFIG_TYPEC)

IS_ENABLED(x) evaluates to 1 when (x == 'y' || x == 'm')
IS_MODULE(x) evaluates to 1 when              (x == 'm')

....this means that a IS_ENABLED(CONFIG_TYPEC) check is enough, and
the latter is redundant.

Regards,
Angelo