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[83.28.83.227]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45491304505sm3198483f8f.22.2026.05.08.02.41.31 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Fri, 08 May 2026 02:41:31 -0700 (PDT) Date: Fri, 8 May 2026 11:41:26 +0200 From: Michal Pecio To: Alan Stern Cc: Dylan Robinson , linux-usb@vger.kernel.org, mathias.nyman@intel.com Subject: Re: [Bug 220748] usb: xhci_queue_isoc_tx_prepare ignore start_frame and always assumes URB_ISO_ASAP is set Message-ID: <20260508114126.68241973.michal.pecio@gmail.com> In-Reply-To: References: <20260507235432.71d28151.michal.pecio@gmail.com> Precedence: bulk X-Mailing-List: linux-usb@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 Thu, 7 May 2026 23:09:18 -0400, Alan Stern wrote: > On Thu, May 07, 2026 at 11:54:32PM +0200, Michal Pecio wrote: > > Alan pointed out that kerneldocs are more up to date, but there is > > still a crucial error there: on ehci-hcd, an URB submitted too late > > completes with -EXDEV instead of the submission failing with -EXDEV. > > I don't remember the details exactly, but are you perhaps not taking > care to distinguish between URBs that are partially too late (some of > their packets' time slots have expired but some have not) and URBs that > are entirely too late (all of their packets' time slots are expired)? > > As I recall, the first case is supposed to complete with some of the > packet statuses set to -EXDEV, whereas in the second case the entire > submission is supposed to fail with -EXDEV. ... which was an artificial distinction requiring drivers to handle substantially the same problem in two ways. They didn't, therefore 24f531371de1 USB: EHCI: accept very late isochronous URBs changed it to EXDEV completion in all cases. AFAIK, this code still stands. I can't find the string "EXDEV" anywhere in ehci-hcd source. Note: every frame start with this status so in case of missed transfer the driver simply leaves it unchanged. Regards, Michal