linux-kernel - Re: Strange problem with tty layer

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Message-ID: <20070126160842.GM7582@csclub.uwaterloo.ca>
Date:	Fri, 26 Jan 2007 11:08:42 -0500
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Paul Fulghum <paulkf@...rogate.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Strange problem with tty layer

On Fri, Jan 26, 2007 at 09:06:52AM -0600, Paul Fulghum wrote:
> ioctl(TIOCSETD/TIOCGETD) sets/returns an integer identifier
> that can be compared agains the N_XXX macros. If you are
> not explicitly setting this then is is probably the default N_TTY.

Yes it is N_TTY (value 0).  I never set it.

> Also at the application level, look at tcsetattr() for setting
> the termios features. Look specifically at the c_cc[VTIME] and c_cc[VMIN]
> members of the termios structure. These settings control how
> much data must be available before returning data to a read().
> Try VTIME=0 and VMIN=1.
> 
> Since your 'missing' data is always on the tail end, maybe
> VMIN is set to 64 or something.

OK, the tty settings according to stty that I am using are:
# stty -F /dev/ttyn0 -a
speed 230400 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl -ixon -ixoff -iuclc -ixany -imaxbel
-opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
-isig -icanon iexten -echo -echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke

So min and time seems good.  I am not explicitly setting those in my
test program (unless one of the other settings implies it).  I will add
it explicitly just in case too.

--
Len Sorensen
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