Re: [PATCH 10/17] driver core: Expose device trust authorization through sysfs

[Jason Gunthorpe]

On Thu, Nov 05, 2026 at 03:43:53PM +0100, Andrew Lunn wrote:
> > Yup, and that's true even in the PCI TDISP case - there's a major amount of
> > "communication" and "configuration" involved in that. The principle which
> > should (hopefully) generalise is that a bus/host controller driver can
> > always interrogate its child device to perform whatever attestation and
> > general configuration is appropriate, but we won't hand off any _control_ of
> > that device to a specific device driver (nor enable potentially-impactful
> > bus-level features like DMA, interrupts, etc. if relevant) without the
> > requisite agreement between the bus code and the user.
> 
> Maybe it would be good to list subsystems which the bus driver can
> use, and cannot use.
> 
> You list interrupts as potentially being dangerous. What about reset
> controllers, GPIOs, regulators? At least in the embedded world, the
> bus driver might need to enable power, set a clock ticking, and take
> the device out of reset via a GPIO, before the device pops into
> existence and will enumerate on the bus.
>
> I don't see why interrupts are dangerous, which makes it hard for me
> to determine if GPIOs and clocks, and regulators are also dangerous?

IMHO we shouldn't try to over think this.

The overall point is to give the userspace a place to inject policy.

Bus drivers should try as hard as they can to contain their child
devices. Like PCIE should activate the iommu, disable ATS. USB should
limit the messages it exchanges, and so on.

When userspace accepts the bus driver it also accepts its containment
capability. So if it accepts one that uses gpio, etc then that's fine.

We are not the point of trying to describe what threat models various
kernel drivers can support. Userspace has to figure that out on their
own.

Jason