I imagine that this is occurring because readline also echos the input:
https://github.com/apache/nuttx-apps/blob/master/system/readline/readline_common.c#L644
The low-level serial driver should not echo just because /isconsole /is
true. Console echo is always handled by the application. I would say
that that is a bug.
From the spec:
https://pubs.opengroup.org/onlinepubs/7908799/xsh/termios.h.html
the serial driver should echo the char if ECHO is enabled. Since NuttX
doesn't follow the spec, it makes many POSIX compliant interactive shells
doesn't work very well.
We have to make the breaking change to fix the wrong initial
implementation.
I still seems like the isconsole does not belong in the conditional:
https://github.com/apache/nuttx/commit/68384e9db42e254b2cf6720bc3380aebdd2b298c
if (dev->isconsole
#ifdef CONFIG_SERIAL_TERMIOS
|| (dev->tc_iflag & ECHO)
#endif
)
{
Currently:
893 if (
894 #ifdef CONFIG_SERIAL_TERMIOS
895 dev->tc_iflag & ECHO
896 #else
897 dev->isconsole
898 #endif
899 )
900 {
If CONFIG_SERIAL_TERMIOS is not set then shouldn't the entire 'if '
condition should be removed?
From my understanding, when CONFIG_SERIAL_TERMIOS isn't set whether serial
driver do some special terminal handling(e.g. \n<->\r\n and echo) is
controlled by isconsole flag:
1. isconsole equals false, all special handling is disable
2. isconsole equals true, all special handling is enable
So, the check needs to be kept to ensure that non-console uart doesn't add
the unxpected process.
If CONFIG_SERIAL_TERMIOS is not selected then non-consoles will do
nothing. In order to restore legacy behavior you would have to do this:
+#ifdef CONFIG_SERIAL_TERMIOS
if (
-#ifdef CONFIG_SERIAL_TERMIOS
dev->tc_iflag & ECHO
-#else - dev->isconsole -#endif
)
...
}
+#endif
That should eliminate the double character echo.
I suppose that you could also eliminate the echo in readline() (and cle()???)
but that would probably mess up the command line editing since the in the edit
commands would also be echoed by the serial driver.
By the way, the reason that this is implemented in a non-standard way like this
with a flag is historical. The serial driver is one of the older parts of the
system. There was no TERMIOS support in NuttX until much, much later in the
development. The serial driver was just a flat, read/write character device
like any other. readline() fakes all the the necessary operations of raw mode
and other termios settings.
