Re: [Question] Status of user-space dynamic overlays API

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 2111 bytes --]

On Mon, Feb 24, 2025 at 03:39:41PM +0530, Ayush Singh wrote:
> On 2/24/25 14:07, Geert Uytterhoeven wrote:
> 
> > Hi Ayush,
> > 
> > On Sat, 22 Feb 2025 at 21:14, Ayush Singh <ayush@beagleboard.org> wrote:
> > > # Challenges
> > > 
> > > ## Security
> > > 
> > > The concerns regarding security seemed to show up in the other
> > > proposals. There was a proposal to have a devicetree property to
> > > allow/deny the application of overlays in some nodes, with default being
> > > deny. Was it insufficient?
> > This is the most important issue: using DT overlays, you can change
> > about anything.  There is no protection yet to limit this to e.g. the
> > expansion connectors on your board.
> > This is what the various WIP "connector" abstractions are trying
> > to solve.
> 
> Thanks for clarifying. However, as I mentioned above, there are usecases for
> dynamic overlays outside of connectors. Specifically, for the usecase of
> connecting random sensors to board pins. I do agree that any fairly well
> specified connector should probably have it's own drivers rather than using
> a generic userspace API.

I'm not sure that's just due to an insuffuciently broad conception of
what a "connector" might be.  Note that to justify a dynamic overlay
interface specifically you need to have *both*
  1) a need to update *anywhere* in the device tree and
  2) to do so at runtime, under userspace control

It's kind of hard to see why you'd need (2) in cases that don't at
some physical level involve a "connector".. in which case (1) is hard
to justify.

How are these sensors being connected to random board pins?  If it's
because those pins are exposed on some header, then it seems like it
ought to fall within the definition of a connector.  If someone is
just soldering onto them, it seems like an semi-permanent change that
would be better handled at boot time.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]