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Date:   Tue, 14 Jun 2022 11:10:01 +0300
From:   Heikki Krogerus <heikki.krogerus@linux.intel.com>
To:     Prashant Malani <pmalani@chromium.org>
Cc:     linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        bleung@chromium.org, swboyd@chromium.org,
        kernel test robot <lkp@intel.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
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        <angelogioacchino.delregno@collabora.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
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Subject: Re: [PATCH v2 2/7] usb: typec: mux: Add CONFIG guards for functions
Message-ID: <YqhCWXOpuOjxwpwp@kuha.fi.intel.com>
References: <20220609181106.3695103-1-pmalani@chromium.org>
 <20220609181106.3695103-3-pmalani@chromium.org>
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In-Reply-To: <20220609181106.3695103-3-pmalani@chromium.org>
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Hi,

On Thu, Jun 09, 2022 at 06:09:41PM +0000, 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.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Prashant Malani <pmalani@chromium.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)
> +
>  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
> +
> +static inline struct typec_mux *fwnode_typec_mux_get(struct fwnode_handle *fwnode,
> +				       const struct typec_altmode_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}

The mux is optional resource for the drivers - fwnode_typec_mux_get()
returns NULL if there is no mux for the caller - so it's better to
just return NULL from this stub.

> +static inline void typec_mux_put(struct typec_mux *mux) {}
> +
> +static inline int typec_mux_set(struct typec_mux *mux, struct typec_mux_state *state)
> +{
> +	return -EOPNOTSUPP;
> +}

Return 0 in this case. That way this stub matches the function
behaviour:

        ...
        if (IS_ERR_OR_NULL(mux))
                return 0;
        ...

> +static inline struct typec_mux *
> +typec_mux_get(struct device *dev, const struct typec_altmode_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}

You don't need this one. Just leave the original outside of the ifdef.
It's already an inline wrapper function.

> +static inline struct typec_mux_dev *
> +typec_mux_register(struct device *parent, const struct typec_mux_desc *desc)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +static inline void typec_mux_unregister(struct typec_mux_dev *mux) {}
> +
> +static inline void typec_mux_set_drvdata(struct typec_mux_dev *mux, void *data) {}
> +static inline void *typec_mux_get_drvdata(struct typec_mux_dev *mux)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +
> +#endif /* CONFIG_TYPEC */
> +
>  #endif /* __USB_TYPEC_MUX */

thanks,

-- 
heikki