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Date: Thu, 26 Mar 2009 09:57:18 -0600 From: Paul Fulghum <paulkf@...rogate.com> To: Paul Rolland <rol@...917.net> CC: linux-kernel@...r.kernel.org Subject: Re: Linux 2.6.x - Serial port signalling not maintained when closing device Paul Rolland wrote: > I'm using small devices that are connected on the serial port, and powered > using RTS and DTR. > When using kernel 2.4.x (at least 2.4.31), I could easily control the > powering of the device using : > stty -F /dev/ttyS0 ospeed 9600 (this would put RTS and DTR to 1 / power) > and > stty -F /dev/ttyS0 ospeed 0 (this would turn it off). > > I've recently updated one of the machine to a new 2.6.29 kernel, and this > is not working anymore. > As far as I can see, I need to have an application that keeps /dev/ttyS0 > open for this to work. As soon as no application is using the port, > everything goes down again. Are you explicitly clearing the HUPCL flag? (stty -F /dev/ttyS0 -hupcl) I just did a quick test on 2.6.22 and DTR/RTS are maintained with your commands above, but only after clearing HUPCL. -- Paul Fulghum MicroGate Systems, Ltd. =Customer Driven, by Design= (800)444-1982 (512)345-7791 (Direct) (512)343-9046 (Fax) Central Time Zone (GMT -5h) www.microgate.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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