linux-kernel - Re: [PATCH v4 1/9] drm/bridge: Allow using fwnode API to get the next bridge

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Message-ID: <xsfrnucued63q2amv7betkvgks6bhssubhjcryghkcloytixj4@ukmak4xwyjtg>
Date: Mon, 22 Apr 2024 22:51:41 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Sui Jingfeng <sui.jingfeng@...ux.dev>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Phong LE <ple@...libre.com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/9] drm/bridge: Allow using fwnode API to get the
 next bridge

On Tue, Apr 23, 2024 at 03:18:55AM +0800, Sui Jingfeng wrote:
> Currently, the various display bridge drivers rely on OF infrastructures
> to works very well, yet there are platforms and/or devices absence of 'OF'
> support. Such as virtual display drivers, USB display apapters and ACPI
> based systems etc.
> 
> Add fwnode based helpers to fill the niche, this allows part of the display
> bridge drivers to work across systems. As the fwnode API has wider coverage
> than DT counterpart and the fwnode graphs are compatible with the OF graph,
> so the provided helpers can be used on all systems in theory. Assumed that
> the system has valid fwnode graphs established before drm bridge drivers
> are probed, and there has fwnode assigned to involved drm bridge instance.
> 
> Signed-off-by: Sui Jingfeng <sui.jingfeng@...ux.dev>
> ---
>  drivers/gpu/drm/drm_bridge.c | 74 ++++++++++++++++++++++++++++++++++++
>  include/drm/drm_bridge.h     | 16 ++++++++
>  2 files changed, 90 insertions(+)
> 

[skipped]

> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 4baca0d9107b..a3f5d12a308c 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -26,6 +26,7 @@
>  #include <linux/ctype.h>
>  #include <linux/list.h>
>  #include <linux/mutex.h>
> +#include <linux/of.h>
>  
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_encoder.h>
> @@ -721,6 +722,8 @@ struct drm_bridge {
>  	struct list_head chain_node;
>  	/** @of_node: device node pointer to the bridge */
>  	struct device_node *of_node;
> +	/** @fwnode: fwnode pointer to the bridge */
> +	struct fwnode_handle *fwnode;

My comment is still the same: plese replace of_node with fwnode. It is
more intrusive, however it will lower the possible confusion if the
driver sets both of_node and fwnode. Also it will remove the necessity
for helpers like drm_bridge_set_node().

>  	/** @list: to keep track of all added bridges */
>  	struct list_head list;
>  	/**
> @@ -788,6 +791,13 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  		      struct drm_bridge *previous,
>  		      enum drm_bridge_attach_flags flags);
>  
> +static inline void
> +drm_bridge_set_node(struct drm_bridge *bridge, struct fwnode_handle *fwnode)
> +{
> +	bridge->fwnode = fwnode;
> +	bridge->of_node = to_of_node(fwnode);
> +}
> +
>  #ifdef CONFIG_OF
>  struct drm_bridge *of_drm_find_bridge(struct device_node *np);
>  #else
> @@ -797,6 +807,12 @@ static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np)
>  }
>  #endif
>  
> +struct drm_bridge *
> +drm_bridge_find_by_fwnode(struct fwnode_handle *fwnode);
> +
> +struct drm_bridge *
> +drm_bridge_find_next_bridge_by_fwnode(struct fwnode_handle *fwnode, u32 port);
> +
>  /**
>   * drm_bridge_get_next_bridge() - Get the next bridge in the chain
>   * @bridge: bridge object
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry