On Wed, 6 Apr 2022, Jiri Slaby wrote:
> On 05. 04. 22, 12:24, Ilpo Järvinen wrote:
> > After lookahead for XON/XOFF characters is added by the next
> > patch, the receive side needs to ensure the flow-control
> > actions are not retaken later on when those same characters
> > get read by TTY.
> >
> > Thus, pass lookahead count to receive_buf and skip
> > flow-control character actions if already taken for the
> > character in question. Lookahead count will become live after
> > the next patch.
> ...
> > --- a/include/linux/tty_ldisc.h
> > +++ b/include/linux/tty_ldisc.h
> > @@ -224,11 +224,11 @@ struct tty_ldisc_ops {
> > * The following routines are called from below.
> > */
> > void (*receive_buf)(struct tty_struct *tty, const unsigned char
> > *cp,
> > - const char *fp, int count);
> > + const char *fp, int count, int
> > lookahead_count);
> > void (*write_wakeup)(struct tty_struct *tty);
> > void (*dcd_change)(struct tty_struct *tty, unsigned int status);
> > int (*receive_buf2)(struct tty_struct *tty, const unsigned char
> > *cp,
> > - const char *fp, int count);
> > + const char *fp, int count, int
> > lookahead_count);
>
> Please always use unsigned if you don't expect negative numbers. count should
> be changed to unsigned in long term too.
Ok. I had just used the same types as there were previously. The types are
a big mess, int and size_t conversions being done back and forth within
that callchain for count. And now that you mentioned unsigned it
seems that fp (flag ptr) is also inconsistent.
> > diff --git a/include/linux/tty_port.h b/include/linux/tty_port.h
> > index 58e9619116b7..1871a6a9cb00 100644
> > --- a/include/linux/tty_port.h
> > +++ b/include/linux/tty_port.h
> > @@ -39,7 +39,7 @@ struct tty_port_operations {
> > };
> > struct tty_port_client_operations {
> > - int (*receive_buf)(struct tty_port *port, const unsigned char *, const
> > unsigned char *, size_t);
> > + int (*receive_buf)(struct tty_port *port, const unsigned char *, const
> > unsigned char *, size_t, size_t);
>
> Good, here it is unsigned and even of size_t size (I don't immediately see
> why, but OK).
You mean that the flag ptr is now unsigned char * (which I didn't even
touch)?
Your comment leaves me to wonder though, what you now want for the
lookahead count (the last arg), size_t or unsigned int? Lookahead count
cannot be negative, and AFAICT, count neither because that would mean tty
has to return some characters back :-).
...Maybe I'll do another patch post these fix ones to match/correct the
types.
--
i.
