linux-kernel - ttyUSB sendbreak problem

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Message-ID: <4999F6C8.3050001@sysnux.pf>
Date:	Mon, 16 Feb 2009 13:29:12 -1000
From:	Jean-Denis Girard <jd.girard@...nux.pf>
To:	linux-kernel <linux-kernel@...r.kernel.org>
CC:	linux-usb@...r.kernel.org
Subject: ttyUSB sendbreak problem

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Hi list,

I'm writing a program which communicates via modem with an embedded
device (electrical network monitoring). The frames are terminated by a
BREAK.

My program works fine when I use a Cyclades 8Yo multiports card, but
fails using USB to serial adapters (tried with pl2303 and FTDI
converters). I suspect that the BREAK are not passed correctly, but I
don't have equipment to check.

I've tried with:
 tcsendbreak(modem,0);
 ioctl(modem, TCSBRK,0);
 ioctl(modem, TCSBRKP, 0);

- From pl2303 debug mode, I see that pl2303_break_ctl is called:
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break on
 drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
 drivers/usb/serial/pl2303.c: pl2303_send - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break off

I found a few references of similar problems in the past, but it was for
older kernels (I'm using 2.6.28.4), so the question remains: should it
work or is there a known problem sending BREAK using ttyUSB?


Thanks,
- --
Jean-Denis Girard

SysNux                  Systèmes  Linux  en Polynésie française
http://www.sysnux.pf/   Tél: +689 50 10 40 / GSM: +689 79 75 27
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