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Date: Thu, 8 Sep 2005 23:01:36 -0400
From: Christopher Faylor <cgf-no-personal-reply-please@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Please try a snapshot - stty issue
Message-ID: <20050909030136.GC18908@trixie.casa.cgf.cx>
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References: <9ED26B1C-5449-42D3-B498-454134FFF08F@rehley.net>
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On Thu, Sep 08, 2005 at 06:47:07PM -0700, Peter Rehley wrote:
>Hi,
>
>I tried stty on snapshot 20050908 and I still get an error message:
>
>stty -F /dev/ttyS0 9600 ; # Different baud then current baud.
>stty: /dev/ttyS0: unable to perform all requested operations.
>
>If I issue the same command a second time I get no error message.
>
>I've traced the problem to /usr/include/sys/termios.h in the  
>cfsetispeek and cfsetospeed macros.  These set c_ispeed and c_ospeed  
>values to set the baud rate, but the baud rate is also stored in  
>c_cflag, and that value is not being set by these macros.  It gets  
>set when tcgetattr is called.
>
>When stty does a compare to see if the change was successfull it sees  
>the original c_cflag and compares to the changed c_cflag and finds  
>that they are different and issues the error message.... actually it  
>does a simply memory compare, but these c_cflag values are different.
>
>One fix would be to change the macros so that they set the baud rate  
>i  c_cflag...of course stty (coreutils) would need to be recompiled  
>for that changed to be picked up.

Since Cygwin always uses the c_ospeed value when setting the baud,
whatever shows up in c_cflag is meaningless.  So, I've just refrained
from setting the CBAUD part of this field.  I don't know if this will
break something else but it seems to work with stty.

While I was at it, I got 'stty -F /dev/ttyS0 -a' working, too.

These changes will be in the next snapshot.

Thanks for tracking this down.

cgf

cgf

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