Re: RE: Re:RE: [PATCH] pinctrl: mcp23s08: reject devices without match data

[Andy Shevchenko]

+Cc: Danilo
(as you were involved in cleaning this up in the past and being co-maintainer
 of driver core)

On Sun, Oct 04, 2026 at 01:06:07AM +0200, Linus Walleij wrote:
> On Fri, Oct 2, 2026 at 12:19 PM Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> > On Fri, Oct 02, 2026 at 11:52:41AM +0200, Linus Walleij wrote:
> > > On Fri, Oct 2, 2026 at 8:59 AM Andy Shevchenko

...

> > > The entire name of the thing feels like debugfs-footgun
> > > territory for example.
> >
> > Yeah, I can't find neither a thing on LWN.net nor in the in-tree documentation.
> > The only useful piece of information is (in kernel-doc of struct bus_type):
> >
> >   driver_override
> >     Set to true if this bus supports the driver_override mechanism, which
> >     allows userspace to force a specific driver to bind to a device via a sysfs
> >     attribute.
> 
> This whole thing is weird, but OK.
> 
> Since we have a ton of drivers depending on match data we either
> have to patch them all to bail out if match data is NULL (like this
> patch does) or, which is equivalent, opt out of driver_override
> that much is certain.
> 
> What I don't get is what this is intended for. What is the use case?
> The commit says this is for VFIO. Shouldn't it be opt-in and turned
> on only for VFIO then?
> 
> Kim Phillips is listed as contract for the platform bus driver_override
> so let's ask! Kim: what is this for?
> 
> All of the device tree drivers use the platform bus, what's yhe
> Unique Selling Point of this for our devices?

-- 
With Best Regards,
Andy Shevchenko