Re: [PATCH 1/5] drm/bridge: allow hpd_notify() to suppress connector hotplug events

From: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
To: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Robert Foss <rfoss@kernel.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Luca Ceresoli <luca.ceresoli@bootlin.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
	Kevin Hilman <khilman@baylibre.com>,
	Jerome Brunet <jbrunet@baylibre.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Rob Clark <robin.clark@oss.qualcomm.com>,
	Dmitry Baryshkov <lumag@kernel.org>,
	Abhinav Kumar <abhinav.kumar@linux.dev>,
	Jessica Zhang <jesszhan0024@gmail.com>,
	Sean Paul <sean@poorly.run>,
	Marijn Suijten <marijn.suijten@somainline.org>,
	Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konradybcio@kernel.org>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	linux-amlogic@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org
Subject: Re: [PATCH 1/5] drm/bridge: allow hpd_notify() to suppress connector hotplug events
Date: Sun, 12 Jul 2026 13:21:51 +0300	[thread overview]
Message-ID: <cgk2httvebzm2jnjnb437mutez66tfozzdk77mjwukfzngdioh@mu46u3pwlf2u> (raw)
In-Reply-To: <20260629-msm-dp-msttypec-v1-1-646a10256233@oss.qualcomm.com>

On Mon, Jun 29, 2026 at 10:48:03PM +0800, Yongxing Mou wrote:
> The bridge connector framework currently invokes all bridge
> hpd_notify() callbacks and unconditionally emits a connector hotplug
> event afterwards.
> 
> However, not every HPD notification requires a userspace hotplug event.
> 
> In particular, DP MST bridges may use hpd_notify() to propagate HPD and
> IRQ notifications through the bridge chain while the actual hotplug
> handling is performed by the DRM DP MST core. Connector creation,
> removal and userspace hotplug events are already managed by the MST
> topology framework.
> 
> Allow hpd_notify() implementations to suppress the bridge connector
> hotplug event by introducing a bool *send_hotplug parameter. Drivers
> can clear this flag when HPD processing should not result in a
> connector hotplug notification.

Why? Worst case the kernel receives another hotplug notification which
gets ignored by the driver.

> 
> A NULL pointer indicates that hotplug suppression is not supported by
> the caller, such as the connector detect polling path.

And nothing in this patch makes any use of it. I'd say, it's
questionable addition. Let me check other patches...

> 
> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
> ---
>  drivers/gpu/drm/bridge/lontium-lt9611uxc.c     |  3 ++-
>  drivers/gpu/drm/display/drm_bridge_connector.c | 15 +++++++++------
>  drivers/gpu/drm/meson/meson_encoder_hdmi.c     |  3 ++-
>  drivers/gpu/drm/msm/dp/dp_display.c            |  3 ++-
>  drivers/gpu/drm/msm/dp/dp_drm.h                |  3 ++-
>  drivers/gpu/drm/omapdrm/dss/hdmi4.c            |  3 ++-
>  include/drm/drm_bridge.h                       |  3 ++-
>  7 files changed, 21 insertions(+), 12 deletions(-)

-- 
With best wishes
Dmitry

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