On 7/11/2021 12:24 PM, Eli Zaretskii wrote:
>> From: Ken Brown <kbrown@cornell.edu>
>> Date: Sun, 11 Jul 2021 11:24:58 -0400
>>
>> Fmake_serial_process calls Fserial_process_configure, which calls
>> serial_configure, which calls cfsetspeed with the speed argument equal to the
>> numerical baud rate (e.g., 9600).  But the documentation of cfsetspeed says that
>> the speed argument must be one of the Bnnn constants defined in termios.h (e.g.,
>> B9600).  See, for example,
>>
>>     https://man7.org/linux/man-pages/man3/termios.3.html
>>
>> This incorrect call of cfsetspeed happens to succeed on GNU/Linux because
>> glibc's cfsetspeed allows the argument to be the numerical baud rate, which it
>> converts to the appropriate Bnnn constant.  But I don't think emacs should be
>> relying on this undocumented behavior.  In particular, this doesn't work on
>> Cygwin.  And it wouldn't even work on GNU/Linux if emacs used the cfsetspeed
>> replacement defined in sysdep.c instead of glibc's cfsetspeed.
>>
>> I think the way to fix this is to imitate the glibc code that converts the baud
>> rate to a Bnnn constant, but maybe someone has a better idea.
> 
> Converting in sysdep.c:serial_configure sounds TRT to me.

Patch attached.

Ken