linux-kernel - Re: [PATCH v6 13/26] drm/encoder: add drm_encoder_cleanup

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Message-ID: <spxzxwcs27uv2ttt5mh3r2767ihczvzzrtov6afdmex2ye7lam@r6kdqv5ocg5h>
Date: Fri, 7 Feb 2025 05:03:13 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Simona Vetter <simona@...ll.ch>, Inki Dae <inki.dae@...sung.com>, 
	Jagan Teki <jagan@...rulasolutions.com>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, Daniel Thompson <danielt@...nel.org>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Jonathan Corbet <corbet@....net>, 
	Sam Ravnborg <sam@...nborg.org>, Boris Brezillon <bbrezillon@...nel.org>, 
	Nicolas Ferre <nicolas.ferre@...rochip.com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, 
	Claudiu Beznea <claudiu.beznea@...on.dev>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Paul Kocialkowski <contact@...lk.fr>, Maxime Ripard <mripard@...nel.org>, 
	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>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Hervé Codina <herve.codina@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: Re: [PATCH v6 13/26] drm/encoder: add drm_encoder_cleanup_from()

On Thu, Feb 06, 2025 at 07:14:28PM +0100, Luca Ceresoli wrote:
> Supporting hardware whose final part of the DRM pipeline can be physically
> removed requires the ability to detach all bridges from a given point to
> the end of the pipeline.
> 
> Introduce a variant of drm_encoder_cleanup() for this.
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> 
> ---
> 
> Changes in v6: none
> Changes in v5: none
> Changes in v4: none
> Changes in v3: none
> 
> Changed in v2:
>  - fix a typo in a comment
> ---
>  drivers/gpu/drm/drm_encoder.c | 21 +++++++++++++++++++++
>  include/drm/drm_encoder.h     |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> index 8f2bc6a28482229fd0b030a1958f87753ad7885f..472dfbefe2960924a4e83bec425af8c7ef5f5265 100644
> --- a/drivers/gpu/drm/drm_encoder.c
> +++ b/drivers/gpu/drm/drm_encoder.c
> @@ -207,6 +207,27 @@ void drm_encoder_cleanup(struct drm_encoder *encoder)
>  }
>  EXPORT_SYMBOL(drm_encoder_cleanup);
>  
> +/**
> + * drm_encoder_cleanup_from - remove a given bridge and all the following
> + * @encoder: encoder whole list of bridges shall be pruned
> + * @bridge: first bridge to remove
> + *
> + * Removes from an encoder all the bridges starting with a given bridge
> + * and until the end of the chain.
> + *
> + * This should not be used in "normal" DRM pipelines. It is only useful for
> + * devices whose final part of the DRM chain can be physically removed and
> + * later reconnected (possibly with different hardware).
> + */
> +void drm_encoder_cleanup_from(struct drm_encoder *encoder, struct drm_bridge *bridge)
> +{
> +	struct drm_bridge *next;
> +
> +	list_for_each_entry_safe_from(bridge, next, &encoder->bridge_chain, chain_node)
> +		drm_bridge_detach(bridge);
> +}
> +EXPORT_SYMBOL(drm_encoder_cleanup_from);

Shouldn't drm_encoder_cleanup() also use this function?

> +
>  static void drmm_encoder_alloc_release(struct drm_device *dev, void *ptr)
>  {
>  	struct drm_encoder *encoder = ptr;
> diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
> index 977a9381c8ba943b4d3e021635ea14856df8a17d..bafcabb242674880a97dfb62a50d93cc4d80c1d4 100644
> --- a/include/drm/drm_encoder.h
> +++ b/include/drm/drm_encoder.h
> @@ -320,6 +320,7 @@ static inline struct drm_encoder *drm_encoder_find(struct drm_device *dev,
>  }
>  
>  void drm_encoder_cleanup(struct drm_encoder *encoder);
> +void drm_encoder_cleanup_from(struct drm_encoder *encoder, struct drm_bridge *bridge);
>  
>  /**
>   * drm_for_each_encoder_mask - iterate over encoders specified by bitmask
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry