linux-kernel - Re: [PATCH v14 03/10] drm/display: Add Type-C switch helpers

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Message-ID: <ZBrgD61p/p17IOJL@smile.fi.intel.com>
Date:   Wed, 22 Mar 2023 13:01:35 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Pin-yen Lin <treapking@...omium.org>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Xin Ji <xji@...logixsemi.com>, linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-acpi@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Lyude Paul <lyude@...hat.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Allen Chen <allen.chen@....com.tw>,
        dri-devel@...ts.freedesktop.org, Marek Vasut <marex@...x.de>,
        Stephen Boyd <swboyd@...omium.org>,
        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
        Andi Shyti <andi.shyti@...ux.intel.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Imre Deak <imre.deak@...el.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        YueHaibing <yuehaibing@...wei.com>
Subject: Re: [PATCH v14 03/10] drm/display: Add Type-C switch helpers

On Wed, Mar 22, 2023 at 06:46:32PM +0800, Pin-yen Lin wrote:
> Add helpers to register and unregister Type-C "switches" for bridges
> capable of switching their output between two downstream devices.
> 
> The helper registers USB Type-C mode switches when the "mode-switch"
> and the "reg" properties are available in Device Tree.

...

> +config DRM_DISPLAY_DP_TYPEC_HELPER

> +	bool
> +	default y

	def_bool y

> +	depends on DRM_DISPLAY_HELPER
> +	depends on DRM_DISPLAY_HELPER=TYPEC || TYPEC=y
> +	help
> +	  DRM display helpers for USB Type-C Displayport Alternate mode.

Hmm... Dunno if this help is enough.

...

> +	snprintf(name, sizeof(name), "%pfwP-%u", fwnode, port_num);

Would it be possible to have a dup in name and would it be a problem if so?

...

> +/**
> + * drm_dp_register_typec_switches() - register Type-C switches
> + * @dev: Device that registers Type-C switches
> + * @port: Device node for the switch
> + * @switch_desc: A Type-C switch descriptor
> + * @data: Private data for the switches
> + * @mux_set: Callback function for typec_mux_set
> + *
> + * This function registers USB Type-C switches for DP bridges that can switch
> + * the output signal between their output pins. This function uses devm_kcalloc
> + * to allocate memory, so it is expected to only call this in the driver probe
> + * functions.
> + *
> + * Currently only mode switches are implemented, and the function assumes the
> + * given @port device node has endpoints with "mode-switch" property.
> + * The port number is determined by the "reg" property of the endpoint.

`kernel-doc -v ...` should complain on absence of "Return" section.

> + */

...

> +	switch_desc->typec_ports = devm_kcalloc(dev, switch_desc->num_typec_switches,
> +						sizeof(struct drm_dp_typec_port_data),

						sizeof(*switch_desc_typec_ports),

?

> +						GFP_KERNEL);
> +	if (!switch_desc->typec_ports)
> +		return -ENOMEM;

...

> +#ifdef CONFIG_DRM_DISPLAY_DP_TYPEC_HELPER

Ah, maybe this should use IS_REACHABLE() ?

> +void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc);
> +int drm_dp_register_typec_switches(struct device *dev, struct fwnode_handle *port,
> +				   struct drm_dp_typec_switch_desc *switch_desc,
> +				   void *data, typec_mux_set_fn_t mux_set);
> +#else
> +static inline void drm_dp_unregister_typec_switches(struct drm_dp_typec_switch_desc *switch_desc)
> +{
> +}
> +static inline int drm_dp_register_typec_switches(
> +		struct device *dev, struct fwnode_handle *port,
> +		struct drm_dp_typec_switch_desc *switch_desc, void *data,
> +		typec_mux_set_fn_t mux_set)
> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif

-- 
With Best Regards,
Andy Shevchenko