Hi, Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> writes: > On 14.12.2017 20:12, Alan Stern wrote: >> On Thu, 14 Dec 2017, Mathias Nyman wrote: >> >>> Clear Feature Endpoint Halt should reset the data toggle even if the >>> endpoint isn't halted. Host should manage to clear the host side data >>> toggle to keep in sync with the device. >>> >>> Test by sending a "3 data packet URB" before and after clearing the halt. >>> this should create a toggle sequence with two consecutive DATA0 packets. >>> >>> A successful test sequence looks like this >>> ClearFeature(ENDPOINT_HALT) - initial toggle clear >>> DATA0 (max packet sized) >>> DATA1 (max packet sized) >>> DATA0 (zero length packet) >>> ClearFeature(ENDPOINT_HALT) - resets toggle >>> DATA0 (max packet sized), if clear halt fails then toggle is DATA1 >>> DATA1 (max packet sized) >>> DATA0 (zero length packet) >>> >>> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> >> >> This test is a little unusual in that it doesn't contain a way to >> detect failures. That is, you can't tell from the test results whether >> the device and the host behaved the way they are supposed to (in the >> case of the host, you could use a USB analyzer to find out). >> >> Also, some devices don't handle Clear-Halt requests properly if the >> endpoint isn't already halted. Presumably people wouldn't use one of >> those devices for this test! :-) > > I was hoping that the device (dwc3 with zero gadget in my case) would > somehow react if the host sends a DATA1 packet right after > ClearFeature(ENDPOINT_HALT), but turns out this device accepts it and > continues to work just fine. So I ended up looking at the traffic with that's because we prevent clear halt when endpoint is not halted. That was changed when a problem was found when enumerating against macOS. It may be that we're actually hiding an IP bug by doing that, however I never got an argument strong enough to revert the commit. This, may just be the strong argument I need :-) -- balbi
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