Description of problem: After updating a x86 based system using USB attached
serial devices (based on the PL2303 chipset) from FC6 to FC8, the system started
experiencing character loss on the serial ports.

Version-Release number of selected component (if applicable):

Fedora release 8 (Werewolf)
kernel-2.6.23.15-137.fc8
(also seen with kernel-2.6.23.1-42.fc8)

How reproducible: Very.  Simply logging in via modem would show character loss
in the /etc/issue output.  UUCP (I know, who still uses that?) was the hardest hit:

(2008-02-17 04:33:29.17 32027) ERROR: Timed out waiting for packet
(2008-02-17 04:33:29.17 32027) Errors: header 4, checksum 5, order 0, remote
rejects 2
(2008-02-17 05:03:38.47 4808) ERROR: Timed out waiting for packet
(2008-02-17 05:03:38.47 4808) Errors: header 2, checksum 4, order 0, remote
rejects 1
uucico sopwith mail (2008-02-17 05:18:42.42 4891) ERROR: Timed out waiting for
packet
(2008-02-17 05:18:42.42 4891) Errors: header 0, checksum 0, order 0, remote
rejects 1
(2008-02-17 06:01:59.94 5111) Errors: header 0, checksum 0, order 0, remote
rejects 8
(2008-02-17 06:18:20.86 5162) ERROR: Timed out waiting for packet

Steps to Reproduce:
1. Install FC8
2. Attach a PL2303 USB serial device
3. Use it ;-)
  
Actual results:

Character loss.

Expected results:

No character loss.

Additional info: The problem has already been found and fixed upstream.  Please
see the following changeset:

http://linux.bkbits.net:8080/linux-2.6/?PAGE=cset&REV=47841262cQWC_Dd1dc8leOIwD7_tQg

Here is the summary text for that changeset:

pl2303: Fix mode switching regression

Cleaning out all the incorrect 'no change made' checks for termios
settings showed up a problem with the PL2303. The hardware here seems to
lose sync and bits if you tell it to make no changes. This shows up with
a real world application.

To fix this the driver check for meaningful hardware changes is restored
but doing the tests correctly and as a tty layer function so it doesn't
get duplicated wrongly everywhere if other drivers turn out to need it.

Signed-off-by: Alan Cox <alan>
Tested-by: Mirko Parthey <mirko.parthey.de>
Signed-off-by: Linus Torvalds <torvalds>

GIT: bf5e5834bffc62b50cd4a201804506eb11ef1af8

I applied the referenced changes and built a test kernel.  So far, so good.  No
data loss.  Please roll these changes into the next FC8 kernel as soon as
possible.  I'll attach the patch I built my kernel from (based on the
2.6.23.15-137.fc8 source)