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

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Message-ID: <YqEDALxy2sN0+fxX@chromium.org>
Date:   Wed, 8 Jun 2022 20:13:52 +0000
From:   Prashant Malani <pmalani@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     bleung@...omium.org, swboyd@...omium.org,
        heikki.krogerus@...ux.intel.com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        José Expósito <jose.exposito89@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Maxime Ripard <maxime@...no.tech>,
        Neil Armstrong <narmstrong@...libre.com>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Pin-Yen Lin <treapking@...omium.org>,
        Robert Foss <robert.foss@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        Xin Ji <xji@...logixsemi.com>
Subject: Re: [PATCH 2/7] usb: typec: mux: Add CONFIG guards for functions

On Jun 07 19:00, Prashant Malani wrote:
> 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.
> 
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
>  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..758d34ced1f8 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)
> +
>  struct typec_mux *fwnode_typec_mux_get(struct fwnode_handle *fwnode,
>  				       const struct typec_altmode_desc *desc);
>  void typec_mux_put(struct typec_mux *mux);
> @@ -76,4 +78,40 @@ void typec_mux_unregister(struct typec_mux_dev *mux);
>  void typec_mux_set_drvdata(struct typec_mux_dev *mux, void *data);
>  void *typec_mux_get_drvdata(struct typec_mux_dev *mux);
>  
> +#else
> +
> +struct typec_mux *fwnode_typec_mux_get(struct fwnode_handle *fwnode,
> +				       const struct typec_altmode_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +
> +void typec_mux_put(struct typec_mux *mux) {}
> +
> +int typec_mux_set(struct typec_mux *mux, struct typec_mux_state *state)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline struct typec_mux *
> +typec_mux_get(struct device *dev, const struct typec_altmode_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +
> +struct typec_mux *
> +typec_mux_register(struct device *parent, const struct typec_mux_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +void typec_mux_unregister(struct typec_mux *mux) {}
> +
> +void typec_mux_set_drvdata(struct typec_mux *mux, void *data) {}
> +void *typec_mux_get_drvdata(struct typec_mux *mux)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}

LKP discovered some issues with static inlining as well as older
(incorrect struct). [1]

I will fix this in the next version.

[1]
https://lore.kernel.org/linux-usb/20220607190131.1647511-1-pmalani@chromium.org/T/#m571c46dce2339186967216bd5af25bcf9e6d1380

> +
> +#endif /* CONFIG_TYPEC */
> +
>  #endif /* __USB_TYPEC_MUX */
> -- 
> 2.36.1.255.ge46751e96f-goog
>