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[83.28.46.53]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d1e4e56fesm2551428f8f.27.2026.04.01.14.50.25 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 01 Apr 2026 14:50:25 -0700 (PDT) Date: Wed, 1 Apr 2026 23:50:22 +0200 From: Michal Pecio To: Alan Stern Cc: Thinh Nguyen , Oliver Neukum , =?UTF-8?B?QmrDuHJu?= Mork , USB list Subject: Re: correctly handling EPROTO Message-ID: <20260401235022.67037c98.michal.pecio@gmail.com> In-Reply-To: <20260330143600.0594f0da.michal.pecio@gmail.com> References: <20260318235920.ioek26hdr25rkksp@synopsys.com> <1eaf4cf3-4278-4d04-87aa-8b6069d544e1@rowland.harvard.edu> <20260319231620.3ukqxsrwqikp5zbd@synopsys.com> <2929d47c-fc02-49d2-873e-758f24c43071@rowland.harvard.edu> <20260321021439.7pmcdrpb5oxbivct@synopsys.com> <20260321065424.76a80508.michal.pecio@gmail.com> <20260328222217.297200bd.michal.pecio@gmail.com> <22c70ca7-57dc-4328-a5cc-d46c4f73556f@rowland.harvard.edu> <20260329184611.0afa92c7.michal.pecio@gmail.com> <20260330143600.0594f0da.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 Mon, 30 Mar 2026 14:36:00 +0200, Michal Pecio wrote: > UVC allows both isoc and bulk transport. I have one bulk device and I > found that if I randomly change urb->status to -EPROTO, the URB is not > resubmitted but (on xHCI) the endpoint keeps going, until it stops after > 5 errors (no URBs left). EHCI would presumably never restart at all. I tried this again with real transaction errors (dodgy cable) on EHCI with disabled XactErr retries and I see identical result. Failed URBs are never submitted again (checked with usbmon) but the endpoint keeps going as long as there are other URBs remaining. [285740.194700] usb 4-4: new high-speed USB device number 3 using ehci-pci [285740.243438] usb 4-4: New USB device found, idVendor=345f, idProduct=2130, bcdDevice=21.00 [285740.243448] usb 4-4: New USB device strings: Mfr=1, Product=2, SerialNumber=7 [285740.243452] usb 4-4: Product: USB3 Video [285740.243455] usb 4-4: Manufacturer: UltraSemi [285740.243457] usb 4-4: SerialNumber: 20210621 [285740.263078] uvcvideo 4-4:1.0: Found UVC 1.00 device USB3 Video (345f:2130) [285745.210034] uvcvideo 4-4:1.0: Allocated 5 URB buffers of 30x512 bytes each [285745.563613] ehci-pci 0000:08:00.2: devpath 4 ep3in 3strikes [285745.563667] uvcvideo 4-4:1.1: Non-zero status (-71) in video completion handler. [285745.830190] ehci-pci 0000:08:00.2: devpath 4 ep3in 3strikes [285745.830233] uvcvideo 4-4:1.1: Non-zero status (-71) in video completion handler. [285746.145090] ehci-pci 0000:08:00.2: devpath 4 ep3in 3strikes [285746.145112] uvcvideo 4-4:1.1: Non-zero status (-71) in video completion handler. [285746.500756] ehci-pci 0000:08:00.2: devpath 4 ep3in 3strikes [285746.500778] uvcvideo 4-4:1.1: Non-zero status (-71) in video completion handler. [285746.771547] ehci-pci 0000:08:00.2: devpath 4 ep3in 3strikes [285746.771571] uvcvideo 4-4:1.1: Non-zero status (-71) in video completion handler. # urb1 ffff8881a653ab40 3478085173 C Bi:4:003:3 0 15360 = 0c8d8a89 cd94dc59 d1941900 10801080 10801080 10801080 10801080 10801080 ffff8881a653ab40 3478085194 S Bi:4:003:3 -115 15360 < # urb2 ffff8881be27dd80 3478085930 C Bi:4:003:3 0 15360 = 0c8d8a89 cd943acd d2941a00 10801080 10801080 10801080 10801080 10801080 ffff8881be27dd80 3478085955 S Bi:4:003:3 -115 15360 < # urb3 ffff88814746f840 3478086931 C Bi:4:003:3 0 15360 = 0c8d8a89 cd94fe45 d4941b00 10801080 10801080 10801080 10801080 10801080 ffff88814746f840 3478086995 S Bi:4:003:3 -115 15360 < # urb4 ffff8881617b3480 3478087544 C Bi:4:003:3 0 15360 = 0c8d8a89 cd94fab6 d5941c00 10801080 10801080 10801080 10801080 10801080 ffff8881617b3480 3478087563 S Bi:4:003:3 -115 15360 < # urb1 errors out ffff8881a653ab40 3478087703 C Bi:4:003:3 -71 0 # urb2 ffff8881be27dd80 3478088803 C Bi:4:003:3 0 15360 = 0c8d8a89 cd94f730 d7941d00 10801080 10801080 10801080 10801080 10801080 ffff8881be27dd80 3478088813 S Bi:4:003:3 -115 15360 < # urb3 ffff88814746f840 3478089546 C Bi:4:003:3 0 15360 = 0c8d8a89 cd949cc4 d8941d00 10801080 10801080 10801080 10801080 10801080 ffff88814746f840 3478089554 S Bi:4:003:3 -115 15360 < ... Not sure why it happens, maybe it's just the async giveback race, but it worked like that reliably several times.