Re: [RFC rtw-next 1/2] wifi: rtw89: usb: add hw_info sysfs attribute

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, May 19, 2026 at 02:11:32PM +0200, Johannes Berg wrote:
> Hi,
> 
> > > Example usage from user-space:
> > >   $ cat /sys/bus/usb/devices/2-3.1.2:1.0/hw_info
> > >   SN: 36 42 00 01 23
> > >   UUID: aa ec 2b 7c 0a 55 47 27 8d e0 b3 0f eb cc bb aa
> 
> Sysfs has a "one value per file" rule (soft rule according to the docs,
> but harder in practice, I believe), so seems if anything that should be
> two files. Maybe a UUID should also be formatted as such with %pU or
> similar.

That should be 2 separate sysfs files please.

And yes, use %pU.

And be careful about exposing serial numbers to userspace, some systems
don't like normal users to read them so be sure to get the permissions
correct.  We had to add some USB code for ALLOW_SERIAL_NUMBER to make it
so that systems can handle this if they want to.

And shouldn't this just be the USB serial number to start with?  Why is
there a different string here?  We already have a sysfs file for this
value.

thanks,

greg k-h