On Thu, Apr 18, 2024 at 03:43:49PM +0300, Esa Laakso wrote: > There are some cases where parity selection is required for passing > it forward to a virtualized terminal. In this sepcific use-case, we > want to use pty to send and receive serial data to a serial > multiplexer. By using a pty, we avoid writing a custom tty driver. > > There is very little evidence on the reasoning on why this option is > hard-coded to be disabled. AFAIK it has been as such since 1996. With > the lack of information about why this is, and based on the fact there > are other similar fields that are not hard-coded, it is considered safe > to enable this option. > > Still, in order not to be too intrusive about the change, add it only on > the condition that the termios flag `EXTPROC` is turned on. This way > there is very little chance it will cause any unintended problems in any > other implementation. You need to document that EXTPROC thing somewhere, otherwise someone is going to ask about this in 20 years and be confused :) > Signed-off-by: Esa Laakso <esa.laakso@xxxxxxxxxxx> > Signed-off-by: Esa Laakso <fidelix.laakso@xxxxxxxxx> Do not sign off on something twice, use your real email address only once, that's all that is needed. > --- > > We are looking for some assistance on this patch, or just a green light > to submit it, if it is good to go. > > We would need to know if the change is valid in context of pty, as > there seems to be fairly little information about the reasoning behind > the hard-coded values. > > Our guess is that they have been as such forever and nobody has had a > reason to change them. We have a reason to change them, and we would > like to know if it is safe to do so and possibly contribute in the > process. Either by just using the patch for ourselves or submitting > it here. > > For the record, this is my first patch submitted upstream. Please let > me know if something is incorrect or missing. > --- > > drivers/tty/pty.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c > index 07394fdaf522..e2d9718dcea0 100644 > --- a/drivers/tty/pty.c > +++ b/drivers/tty/pty.c > @@ -267,7 +267,9 @@ static void pty_set_termios(struct tty_struct *tty, > } > } > > - tty->termios.c_cflag &= ~(CSIZE | PARENB); > + tty->termios.c_cflag &= ~(CSIZE); > + if (!L_EXTPROC(tty)) > + tty->termios.c_cflag &= ~(PARENB); Some description of how you tested this in the changelog would also be good, and a comment here too as to what you are doing. thanks, greg k-h
