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pl2303: Fix mode switching regression

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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@redhat.com>
Tested-by: Mirko Parthey <mirko.parthey@informatik.tu-chemnitz.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox
2008-01-08 14:55:51 +00:00
committed by Linus Torvalds
parent cf05946250
commit bf5e5834bf
3 changed files with 27 additions and 0 deletions
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19
drivers/char/tty_ioctl.c
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@@ -364,6 +364,25 @@ void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
EXPORT_SYMBOL(tty_termios_copy_hw);
/**
* tty_termios_hw_change - check for setting change
* @a: termios
* @b: termios to compare
*
* Check if any of the bits that affect a dumb device have changed
* between the two termios structures, or a speed change is needed.
*/
int tty_termios_hw_change(struct ktermios *a, struct ktermios *b)
{
if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
return 1;
if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
return 1;
return 0;
}
EXPORT_SYMBOL(tty_termios_hw_change);
/**
* change_termios - update termios values
* @tty: tty to update