linux-kernel - Re: [PATCH] Winchiphead 340/1: full baud rate and status/control line support

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Message-ID: <87zli693i0.fsf@qurzaw.linpro.no>
Date:	Sun, 04 Jan 2009 22:15:51 +0100
From:	Tollef Fog Heen <tfheen@....no>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, werner@...nelius-consult.de,
	frank@...gswood-consulting.co.uk
Subject: Re: [PATCH] Winchiphead 340/1: full baud rate and status/control line support

]] Alan Cox 

| > +	if (factor > 0xfff0) { /* Clamp */
| > +		factor = 0xfff0;
| > +		divisor = 0;
| > +	}
| > +
| > +	t1 = factor;
| > +	for (t2 = divisor; t2 <= CH341_BAUDBASE_DIVMAX; t2++)
| > +		t1 >>= 3;
| > +	baud = CH341_BAUDBASE_FACTOR / t1;
| > +
| 
| Same question as before: Can baud really become zero at this point ? Also
| for that matter what guarantees that t1 cannot become zero in this
| computation ?

Nothing, that code is completely wrong.  I've rewritten it now.  Thanks
for explaining.

| > +	if (baud && tty)
| > +		tty_encode_baud_rate(tty, baud, baud);
| 
| The check for B0 (hangup) was done earlier (see set_termios). So if you
| can end up with a requested baud rate being turned into 0 you need to
| bump it up to 1. If not you don't need the test.

Indeed, fixed as well.  New patch incoming in a few minutes.

I've also added the mutex protecting set_handshake, but I feel less
confident about whether that's the right approach, so feedback there is
also appreciated.

-- 
Tollef Fog Heen
UNIX is user friendly, it's just picky about who its friends are

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