The CP210X_SET_MHS request cannot be used to control RTS when hardware flow control (auto-RTS) is enabled and instead returns an error which is currently logged as: cp210x ttyUSB0: failed set request 0x7 status: -32 when opening and closing a port (and on TIOCMSET requests). Add a crtscts flag to keep track of the hardware flow-control setting and use it to suppress any request to change RTS when auto-RTS is enabled. Note that RTS is still deasserted when disabling the UART as part of close. Reported-by: Pho Tran <pho.tran@silabs.com> Signed-off-by: Johan Hovold <johan@kernel.org>