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[83.28.83.135]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4994a0fc94esm161020365e9.12.2026.08.04.22.54.32 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 04 Aug 2026 22:54:33 -0700 (PDT) Date: Wed, 5 Aug 2026 07:54:29 +0200 From: Michal Pecio To: Charles Daoust Cc: Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] usb: core: add USB_QUIRK_CONFIG_DESC_READ_255 for Razer BlackShark V3 Pro Message-ID: <20260805075429.08416607.michal.pecio@gmail.com> In-Reply-To: <20260720150207.1963786-1-charles.daoust@gmail.com> References: <20260720150207.1963786-1-charles.daoust@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 20 Jul 2026 11:01:26 -0400, Charles Daoust wrote: > From: Charles D'Aoust > > 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: stable@vger.kernel.org > Signed-off-by: Charles D'Aoust 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