linux-kernel - Re: [PATCH v10 01/11] usb: typec: Add notifier functions

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Message-ID: <462ad1bd-7eec-4f26-b383-96b049e14559@rock-chips.com>
Date: Mon, 24 Nov 2025 09:40:03 +0800
From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Chaoyi Chen <kernel@...kyi.com>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Peter Chen <hzpeterchen@...il.com>, Luca Ceresoli
 <luca.ceresoli@...tlin.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Heiko Stuebner
 <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>,
 Andy Yan <andy.yan@...k-chips.com>,
 Yubing Zhang <yubing.zhang@...k-chips.com>,
 Frank Wang <frank.wang@...k-chips.com>,
 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>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Amit Sunil Dhamne <amitsd@...gle.com>, Dragan Simic <dsimic@...jaro.org>,
 Johan Jonker <jbx6244@...il.com>, Diederik de Haas <didi.debian@...ow.org>,
 Peter Robinson <pbrobinson@...il.com>, linux-usb@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v10 01/11] usb: typec: Add notifier functions

Hi Greg,

On 11/21/2025 10:07 PM, Greg Kroah-Hartman wrote:
> On Thu, Nov 20, 2025 at 10:23:33AM +0800, Chaoyi Chen wrote:
>> From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
>>
>> Some other part of kernel may want to know the event of typec bus.
> Be specific, WHAT part of the kernel will need to know this?

For now, it is DRM.


>
> And why a new notifier, why not just use the existing notifiers that you
> already have?  And what is this going to be used for?

We have discussed this before, but the current bus notifier cannot achieve the expected notification [0].

[0] https://lore.kernel.org/all/aPsuLREPS_FEV3DS@kuha.fi.intel.com/


>
> Notifiers are a pain, and should almost never be added.  Use real
> function calls instead.

In v6, I used direct function calls, but had to switch to notifiers because couldn't resolve the dependencies between DRM and Type-C [1]. Do you have any good ideas? Thank you.

[1] https://lore.kernel.org/all/aPYImGmesrZWwyqh@kuha.fi.intel.com/


>
> thanks,
>
> greg k-h
>
>
-- 
Best,
Chaoyi