usb: device_next: prevent ECHO on Linux Kernel based host #82815
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Fix "warning: 'cdc_acm_send_notification' defined but not used" when Kconfig option UART_USE_RUNTIME_CONFIGURE is not used and properly handle enqueue error. Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
This is similar to the approach implemented for the legacy CDC ACM class commit 0127d00 ("usb: device: cdc_acm: Use ZLP to detect initial host read") but it uses Set Line Coding request to detect client activity on the host side. Suggested-by: Tomasz Moń <tomasz.mon@nordicsemi.no> Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
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area: USB
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This won't really work. Set line coding is in no way required. Please just replicate the ZLP handling as this is the only approach that is guaranteed to work.
Note that some applications may actually want to have the echo. The ZLP is transparent to any application using the tty layer and allows the best possible indication to class implementation that host actually started to read the data on IN endpoint.
That works very well, and not just once. And if there is no line coding request then it is not a Linux host.
Yes, that it how it is implemented. |
The original implementation is completely independent of any control transfers. Your spin-off is depending on Set Line Coding. This is essentially different. Please remove the Set Line Coding dependency. |
This is similar to the approach implemented for the legacy CDC ACM class
commit 0127d00
("usb: device: cdc_acm: Use ZLP to detect initial host read")
but it uses Set Line Coding request to detect client activity on the
host side.
Cherry-picked from #80985