Re: [PATCH] usb: core: add USB_QUIRK_CONFIG_DESC_READ_255 for Razer BlackShark V3 Pro

On Mon, 20 Jul 2026 11:01:26 -0400, Charles Daoust wrote:
> From: Charles D'Aoust <[email protected]>
> 
> The Razer BlackShark V3 Pro wireless headset dongle (1532:0577)
> fingerprints its host during the first enumeration after power-on: if
> the first GET_DESCRIPTOR(CONFIGURATION) request asks for 255 bytes, as
> Windows does, the dongle enables its vendor HID command channel; if it
> sees the 9-byte header-only read that Linux issues, it disables that
> channel for the rest of the power session.  Audio still works in that
> state, but battery reporting and all vendor commands are silently
> ignored, and nothing short of removing power recovers the device:
> resets, re-enumerations and byte-exact replays of complete Windows
> control sessions were all verified not to help.
> 
> Both read lengths are spec-compliant (the device truncates the reply
> to wLength); the firmware was evidently only validated against the
> larger request.

Hmm, so is it fingerprinting of the host or sloppy QA? ;)
Out of curiosity, was this patch AI-generated?

>  The kernel already accommodates this class of
> firmware assumption during enumeration: hub_port_init() reads the
> device descriptor with a 64-byte request because that is what Windows
> does and what many devices expect.
> 
> Add USB_QUIRK_CONFIG_DESC_READ_255, which makes usb_get_configuration()
> request 255 bytes for the initial configuration descriptor read rather
> than USB_DT_CONFIG_SIZE, apply it to 1532:0577, and expose it as
> runtime quirk letter 'r'.  Devices without the quirk are unaffected.
> 
> The trigger was isolated by single-variable bisection on otherwise
> unmodified kernels: with only the widened initial read, the dongle's
> vendor channel comes up enabled on a cold plug with no interface
> drivers bound (bare enumeration only); without it, it never does.
> 
> Cc: [email protected]
> Signed-off-by: Charles D'Aoust <[email protected]>

But anyway, FYI an equivalent quirk is now sitting in Greg KH's queue
of fixes for (presumably) the 7.2 release.

I suspect that Greg would accept one more patch to enable the quirk
by default on your device ID.

Regards,
Michal