netdev - I think I figured out the another bug which manifests itself when low

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Message-ID: <496C67C4.4070501@option.com>
Date:	Tue, 13 Jan 2009 11:07:00 +0100
From:	Denis Joseph Barrow <D.Barow@...ion.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linux USB kernel mailing list <linux-usb@...r.kernel.org>,
	Linux netdev Mailing list <netdev@...r.kernel.org>
Subject: I think I figured out the another bug which manifests itself when
 low_latency is set to 0

Hi Alan,
Admittedly there always was a bug when tty_insert_flip_string runs out of memory when low_latency is set to 0,

After your change I now
need a callback when tty_insert_flip_string has room for more data & I currently I don't get one,
This is needed to execute the code in hso_unthrottle_tasklet i.e. I do flow control by not submitting
read urbs to the modem when TTY_THROTTLED is set. The only way I can see for getting this callback without modifying the tty layer
is setting the TTY_THROTTLED bit if tty_insert_flip_string returns 0, I hope this works.

I'm personally a bit frightened that we may have more bugs/problems that will manifest by setting low_latency to 0,
especially for the guys here running diagnostics over the serial port requiring very high throughput.

-- 
best regards,
D.J. Barrow

Linux Kernel Developer
Option NV, Gaston Geenslaan 14, 3001 Leuven, Belgium

T: +32 16 311 621
F: +32 16 207 164
d.barow@...ion.com
www.option.com

Disclaimer:
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