usb/149675: uftdi doesn't react to break properly
Hans Petter Selasky
hselasky at c2i.net
Sun Aug 15 15:15:34 UTC 2010
On Sunday 15 August 2010 16:31:20 Paul Thornton wrote:
> >Number: 149675
> >Category: usb
> >Synopsis: uftdi doesn't react to break properly
> >Confidential: no
> >Severity: non-critical
> >Priority: medium
> >Responsible: freebsd-usb
> >State: open
> >Class: sw-bug
> >Submitter-Id: current-users
> >Arrival-Date: Sun Aug 15 14:40:00 UTC 2010
> >Originator: Paul Thornton
> >Release: 8.1-RELEASE
> FreeBSD base01.local 8.1-RELEASE FreeBSD 8.1-RELEASE #0: Sun Aug 15
> 09:38:55 UTC 2010 root at base01.local:/usr/src/sys/i386/compile/TEST2
> The same issue is seen with GENERIC kernel
> When setting the BRKINT and ~IGNBRK options on a handle where the
> underlying hardware has an FTDI chipset driven by uftdi and ucom, the
> break condition is not correctly acted upon. The underlying hardware is
> an FTDI FT232BL chip.
> The expected behaviour is that the buffer be flushed on reception of a
> break when BRKINT is used, however the driver appears to behave as if
> BRKINT is clear, as an additional 0x00 byte is seen and the buffer isn't
> FreeBSD 7.2 and 8.0 also exhibit the same behaviour.
> Using the same test program, and same USB hardware, Linux behaves as per
> documentation and flushes the buffer on reception of the break when BRKINT
> is set.
> Connect two machines using ftdi-driven hardware.
> Send a break followed by some data A. Send another break, followed by some
> data B.
> The correct response should be that on the receiver the buffer is flushed
> by both breaks, and a read will only return the data B.
> What is likely to be read, however, is: 0x00 [A A A A A] 0x00 [B B B B B]
> The code I was using which brought this issue to light can be downloaded
> from: http://www.prt.org/dmxrx2.c
Compile a kernel with "options USB_DEBUG". Enable FTDI debugging:
Do you seen any debug prints when sending BREAK?
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