Re: [PATCH v2] usb: core: add USB_QUIRK_NO_BOS for devices that hang on BOS descriptor

[Greg KH <gregkh@linuxfoundation.org>]

On Sun, Dec 28, 2025 at 01:54:34PM +0100, Johannes Brüderl wrote:
> On Mon, Dec 8, 2025 at 9:46 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Dec 08, 2025 at 09:58:55AM +0100, Oliver Neukum wrote:
> > > On 07.12.25 22:12, Greg KH wrote:
> > > > Ok, I can duplicate this here.  Maybe we just don't ask for the BOS
> > > > descriptor if no one needs/asks for it.  I can play with that later and
> > > > see if that helps as I'm sure this isn't going to be the only device
> > > > that can't handle the BOS descriptor if Windows isn't querying for it,
> > > > so we don't want to make a huge quirk table if we don't have to.
> > >
> > > 1. That means we'd let lsusb crash devices. Not a good idea.
> >
> > I don't think that it will crash.  hopefully not, as just reading a
> > descriptor after enumerated shouldn't cause that.  I'll test it out...
> >
> > > 2. It is, unfortunately, possible that firmware authors simply
> > > script a detection sequence. That means devices would crash
> > > if you request a descriptor at a time when Windows would not
> > > request it, not just in general.
> > > I am afraid I need to point you at the horrible example
> > > of HID_ALWAYS_POLL
> >
> > That is horrible, hopefully we don't have to do that here :(
> >
> > thanks,
> >
> > greg k-h
> 
> Hello Greg,
> I apologize for the "blunt bump" of this topic.
> Are you (still) open to considering the quirk ?
> 
> A small number of users have started using the Patch, and it seems to
> solve a real problem.. (ref:
> https://www.reddit.com/r/elgato/comments/1lw1e0v/comment/ntrdjpb/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button)
> 
> Given that the options for 4k60fps recording are very limited for
> Linux these days - I suggest it might be worth it. AFAIK, there's no
> good other option in terms of hardware as of December 2025.
> I understand it's a special quirk for just this device, which is not pretty..
> 
> (Note: i've submitted a v3 patch that addressed the feedback).

Sorry, I haven't had a chance to dig into this due to travel and the
holidays.  Give me a few days to catch up...

thanks,

greg k-h