Re: [PATCH v2 0/5] Add support for GE SUNH hot-pluggable connector (was: "drm: add support for hot-pluggable bridges")

From: Luca Ceresoli
Date: Tue May 14 2024 - 13:11:36 EST


Hello Rob,

On Fri, 10 May 2024 11:44:49 -0500
Rob Herring <robh@xxxxxxxxxx> wrote:

> On Fri, May 10, 2024 at 09:10:36AM +0200, Luca Ceresoli wrote:

[...]

> > 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.

I think I should replace "supported" with "exposed [to user space]". In
other words, there is no user of of_overlay_fdt_apply() /
of_overlay_remove*() in mainline Linux, except in unittest. Would it be
a correct rewording?

> > 2. if enabled, overlay (un)loading exposes several bugs
>
> Hence why there is no general purpose interface.

Absolutely.

Best regards,
Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com