Re: [PATCH] usb-serial/ftdi_sio: fix DTR/RTS line modes

[Gene Heskett]

On Thursday 03 June 2010, Daniel Mack wrote:
>On Thu, Jun 03, 2010 at 01:55:02PM +0200, Daniel Mack wrote:
>> Call set_mctrl() and clear_mctrl() according to the flow control mode
>> selected. This makes serial communication for FT232 connected devices
>> work when CRTSCTS is not set.
>>
>> This fixes a regression introduced by 4175f3e31 ("tty_port: If we are
>> opened non blocking we still need to raise the carrier"). This patch
>> calls the low-level driver's dtr_rts() function which consequently sets
>> TIOCM_DTR | TIOCM_RTS. A later call to set_termios() without CRTSCTS in
>> cflags, however, does not reset these bits, and so data is not actually
>> sent out on the serial wire.
>>
>> Signed-off-by: Daniel Mack <daniel@xxxxxxxx>
>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxx>
>> Cc: Johan Hovold <jhovold@xxxxxxxxx>
>> Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
>> Cc: linux-usb@xxxxxxxxxxxxxxx
>
>Oops. I forgot to Cc: stable@xxxxxxxxxxx
>This is in fact broken since 2.6.31-something.
>
>> ---
>>  drivers/usb/serial/ftdi_sio.c |    4 ++++
>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/usb/serial/ftdi_sio.c
>> b/drivers/usb/serial/ftdi_sio.c index 050211a..79dd1ae 100644
>> --- a/drivers/usb/serial/ftdi_sio.c
>> +++ b/drivers/usb/serial/ftdi_sio.c
>> @@ -2005,6 +2005,8 @@ static void ftdi_set_termios(struct tty_struct
>> *tty, "urb failed to set to rts/cts flow control\n");
>>  		}
>>
>> +		/* raise DTR/RTS */
>> +		set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
>>  	} else {
>>  		/*
>>  		 * Xon/Xoff code
>> @@ -2052,6 +2054,8 @@ static void ftdi_set_termios(struct tty_struct
>> *tty, }
>>  		}
>>
>> +		/* lower DTR/RTS */
>> +		clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
>>  	}
>>  	return;
>>  }
>

How soon can this get in?  I ask because I have been crippled in all 
attempts to use an ftdi adaptor to talk to an old legacy machine I have for 
about that long now. xon/xoff seems completely broken, and 7wire seems to 
scramble things to the point where no null modem cable I have made (and I 
have a book on them) will allow the 7wire flow controls to function.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
"Being against torture ought to be sort of a multipartisan thing."
-- Karl Lehenbauer, as amended by Jeff Daiell, a Libertarian
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