On Thu, Feb 03, 2022 at 03:23:37PM +0100, Tomasz Moń wrote: > Do not set timeout to twice the approximate amount of time to send the > entire FIFO if CTS is enabled. If the caller requested no timeout, e.g. > when userspace program called tcdrain(), then wait without any timeout. > > Premature return from tcdrain() was observed on imx based system which > has 32 character long transmitter FIFO with hardware CTS handling. > > Simple userspace application that reproduces problem has to: > * Open tty device, enable hardware flow control (CRTSCTS) > * Write data, e.g. 26 bytes > * Call tcdrain() to wait for the transmitter > * Close tty device > > The other side of serial connection has to: > * Receive some data, e.g. 10 bytes > * Set RTS output (CTS input from sender perspective) inactive for > at least twice the port timeout > * Try to receive remaining data > > Without this patch, userspace application will finish without any error > while the other side of connection will never receive remaining data. > > Signed-off-by: Tomasz Moń <tomasz.mon@xxxxxxxxxxxxxxx> > --- > drivers/tty/serial/serial_core.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) Note, I do not apply "RFC" patches as obviously the submitter does not think they are good enough to be merged :) thanks, greg k-h
