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814a7b36-bfc1-4dae-8640-3722d8ec6cd6 MIME-Version: 1.0 Message-ID: To: cygwin@cygwin.com Subject: 3.6.4-1.x86_64 Windows 10 serial port issue with initial 0 baudrate Date: Sat, 23 Aug 2025 08:59:59 +0000 X-UI-CLIENT-META-MAIL-DROP: W10= X-Provags-ID: V03:K1:u02GjodLTkTD3R4k/5Be1jWHzmZ9v6+eXkfIrTzD1KT/VhsO676cVRwpSrGjT/T76kC80 dfaaqfOWUx1gezKvcm0YabJifxESN/kOT2RQMHINXtv73vScaJC5ZRwWzDcQymiQcN/DxRYMEbXO sTZPlGwv+d/4ViR0Cshs/H25IYZOSPdaGg1h44Wq+/NRS6P3byzezzHh4z8PeHL88JD+VsrnUavg wF0vkMNEe/SjFPfiRzODbAL/GXQSzHE4DMxa6COkR+fUZ3Ug+lU6F6grcC4vvzItzFXfy+sq1J9w 3vMZc2SugxPuQB0kSEhJK1t9It3ZJ9Q0XJZ3Ob/Alj3viZ6W98n4X96BKUteSX8NCtVBGvy+Oqps 5GnN8growUV UI-OutboundReport: notjunk:1;M01:P0:UmyZKNgk/eA=;/0wHwBe5WTcZMiab2JM4KwNeuc6 UIPEEt7op7wT9h7lfWhunEAGAE1IIQbAtdwvr22txOruCg6z0YVAdX6f86EnOl/Pnjs4+dcN+ e1BHYmNPfgrw70Ao4RiGpAWFffgoYk4lIQ0JRxgTRGB0KG2AHPtUM3a8Vbbx5ox0dIhpDuPBV ACHwLNXVNeBvlmq93Uqg07qePI9luBB/z1+Pi57PkSvDPHgD112We7fCCXcvaNs9SzNEcThWb 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beeing used with cygwin programs (e.g. getty or even python). It seems this is because the baudrate is initially zero after the device has been created: $ /cygdrive/c/Windows/System32/mode.com COM72 Status von Gerät COM72: ----------------------- Baudrate: 0 Parität: None Datenbits: 0 Stoppbits: 1 Timeout: OFF XON/XOFF: OFF CTS-Handshaking: OFF DSR-Handshaking: OFF DSR-Prüfung: OFF DTR-Signal: OFF RTS-Signal: ON This makes tcgetattr fail when beeing used on this device. 119 117652 [main] stty 2325 fcntl: 0 = fcntl(0, 4, 0x10000) 732 118384 [main] stty 2325 fhandler_serial::tcgetattr: Invalid baud rate 0 111 118495 [main] stty 2325 __set_errno: virtual int fhandler_serial::tcgetattr(termios*):1027 setting errno 22 116 118611 [main] stty 2325 tcgetattr: -1 = tcgetattr(0, 0x100419060), errno 22 I assume that allmost all programs use tcgetattr before partially changing parameters in the struct that is returned. I suggest not to make tcgetattr fail in this case, but return B0 instead. User programs will most likely change the bitrate setting anyhow. After setting an initial baudrate with mode.com, the device works well with cygwin. Regards, Stefan Althöfer -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple