From: Rob Herring <robh@kernel.org>
To: Luca Ceresoli <luca.ceresoli@bootlin.com>
Cc: "Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"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>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Maxime Ripard" <mripard@kernel.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"David Airlie" <airlied@gmail.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Derek Kiernan" <derek.kiernan@amd.com>,
"Dragan Cvetic" <dragan.cvetic@amd.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Saravana Kannan" <saravanak@google.com>,
"Paul Kocialkowski" <contact@paulk.fr>,
"Hervé Codina" <herve.codina@bootlin.com>,
"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org,
"Paul Kocialkowski" <paul.kocialkowski@bootlin.com>
Subject: Re: [PATCH v2 0/5] Add support for GE SUNH hot-pluggable connector (was: "drm: add support for hot-pluggable bridges")
Date: Fri, 10 May 2024 11:44:49 -0500 [thread overview]
Message-ID: <20240510164449.GB336987-robh@kernel.org> (raw)
In-Reply-To: <20240510-hotplug-drm-bridge-v2-0-ec32f2c66d56@bootlin.com>
On Fri, May 10, 2024 at 09:10:36AM +0200, Luca Ceresoli wrote:
> Hello,
>
> this series aims at supporting a Linux device with a connector to
> physically add and remove an add-on to/from the main device to augment its
> features at runtime, using device tree overlays.
>
> This is the v2 of "drm: add support for hot-pluggable bridges" [0] which
> was however more limited in scope, covering only the DRM aspects. This new
> series also takes a different approach to the DRM bridge instantiation.
>
> [0] https://lore.kernel.org/all/20240326-hotplug-drm-bridge-v1-0-4b51b5eb75d5@bootlin.com/
>
> Use case
> ========
>
> This series targets a professional product (GE SUNH) that is composed of a
> "main" part running on battery, with the main SoC and able to work
> autonomously with limited features, and an optional "add-on" that enables
> more features by adding more hardware peripherals, some of which are on
> non-discoverable busses such as I2C and MIPI DSI.
>
> The add-on can be connected and disconnected at runtime at any moment by
> the end user, and add-on features need to be enabled and disabled
> automatically at runtime.
>
> The add-on has status pins that are connected to GPIOs on the main board,
> allowing the CPU to detect add-on insertion and removal. It also has a
> reset GPIO allowign to reset all peripherals on the add-on at once.
>
> The features provided by the add-on include a display and a battery charger
> to recharge the battery of the main part. The display on the add-on has an
> LVDS input but the connector between the base and the add-on has a MIPI DSI
> bus, so a DSI-to-LVDS bridge is present on the add-on.
>
> Different add-on models can be connected to the main part, and for this a
> model ID is stored in the add-on itself so the software running on the CPU
> on the main part knows which non-discoverable hardware to probe.
>
> Overall approach
> ================
>
> Device tree overlays appear as the most natural solution to support the
> addition and removal of devices from a running system.
>
> Several features are missing from the mainline Linux kernel in order to
> support this use case:
>
> 1. runtime (un)loading of device tree overlays is not supported
Not true. Device specific applying of overlays has been supported
since we merged DT overlay support. What's not supported is a general
purpose interface to userspace to change any part of the DT at any point
in time.
> 2. if enabled, overlay (un)loading exposes several bugs
Hence why there is no general purpose interface.
> 3. the DRM subsystem assumes video bridges are non-removable
Rob
next prev parent reply other threads:[~2024-05-10 16:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 7:10 [PATCH v2 0/5] Add support for GE SUNH hot-pluggable connector (was: "drm: add support for hot-pluggable bridges") Luca Ceresoli
2024-05-10 7:10 ` [PATCH v2 1/5] dt-bindings: connector: add GE SUNH hotplug addon connector Luca Ceresoli
2024-05-10 8:41 ` Rob Herring (Arm)
2024-05-10 10:37 ` Luca Ceresoli
2024-05-10 13:22 ` Rob Herring
2024-05-10 14:39 ` Luca Ceresoli
2024-05-10 16:36 ` Rob Herring
2024-05-14 16:51 ` Luca Ceresoli
2024-05-10 7:10 ` [PATCH v2 2/5] drm/bridge: add bridge notifier to be notified of bridge addition and removal Luca Ceresoli
2024-05-10 7:10 ` [PATCH v2 3/5] drm/encoder: add drm_encoder_cleanup_from() Luca Ceresoli
2024-05-10 7:10 ` [PATCH v2 4/5] drm/bridge: hotplug-bridge: add driver to support hot-pluggable DSI bridges Luca Ceresoli
2024-05-10 7:10 ` [PATCH v2 5/5] misc: add ge-addon-connector driver Luca Ceresoli
2024-05-10 7:55 ` Greg Kroah-Hartman
2024-05-10 10:24 ` Arnd Bergmann
2024-05-10 10:54 ` Luca Ceresoli
2024-05-10 10:57 ` Arnd Bergmann
2024-05-10 15:32 ` Luca Ceresoli
2024-05-10 10:54 ` Luca Ceresoli
2024-05-10 11:03 ` Greg Kroah-Hartman
2024-05-10 16:44 ` Rob Herring [this message]
2024-05-14 17:11 ` [PATCH v2 0/5] Add support for GE SUNH hot-pluggable connector (was: "drm: add support for hot-pluggable bridges") Luca Ceresoli
2024-05-16 13:22 ` Daniel Vetter
2024-05-20 12:01 ` Luca Ceresoli
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