On Wed, Feb 01, 2023 at 09:30:28AM +0000, Starke, Daniel wrote: > > > Add support for the TIOCMIWAIT ioctl on the virtual ttys. This enables the > > > user to wait for virtual modem signals like RING. > > > > > > Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> > > > --- > > > drivers/tty/n_gsm.c | 32 ++++++++++++++++++++++++++++++++ > > > 1 file changed, 32 insertions(+) > > > > > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > > > index 118511c1fa37..48fb7dad44cd 100644 > > > --- a/drivers/tty/n_gsm.c > > > +++ b/drivers/tty/n_gsm.c > > > @@ -1542,6 +1542,7 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci, > > > if (brk & 0x01) > > > tty_insert_flip_char(&dlci->port, 0, TTY_BREAK); > > > dlci->modem_rx = mlines; > > > + wake_up_interruptible(&dlci->gsm->event); > > > } > > > > > > /** > > > @@ -3848,6 +3849,35 @@ static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk) > > > return -EPROTONOSUPPORT; > > > } > > > > > > +/** > > > + * gsm_wait_modem_change - wait for modem status line change > > > > No need for tabs. > > > > Or for kernel doc for static functions, but that's not a big deal. > > All other functions follow the same style here. Nevertheless, I will > replace the tabs with spaces. Originally, I had planned a code clean-up > after committing all the changes from my original RFC. Ah, ok, nevermind then, I didn't see that as it's not in the diffs. Cleaning up later is fine. > > > +static int gsm_wait_modem_change(struct gsm_dlci *dlci, u32 mask) > > > +{ > > > + struct gsm_mux *gsm = dlci->gsm; > > > + u32 old = dlci->modem_rx & mask; > > > + int ret; > > > + > > > + if (gsm->dead) > > > + return -ENODEV; > > > + > > > + do { > > > + ret = wait_event_interruptible(gsm->event, gsm->dead > > > + || old ^ (dlci->modem_rx & mask)); > > > + if (ret) > > > + return ret; > > > + if (dlci->state != DLCI_OPEN) > > > + return -EL2NSYNC; > > > + if (gsm->dead) > > > + return -ENODEV; > > > + } while ((old ^ (dlci->modem_rx & mask)) == 0); > > > > No way to break out of the loop if it goes for forever? > > I assume that this is the expected behavior for TIOCMIWAIT. The functions > returns if: > - the requested modem signal changed > - the wait function got interrupted (e.g. by a signal) > - the underlying DLCI was closed > - the underlying ldisc device was removed Hm, I guess you are right. But wow, reading that wait_event_interruptible() condition is crazy, please document that really well to explain this properly so you will be able to understand it in a year when you next have to fix it up :) > I can add that the function returns immediate if a mask has been passed > which matches no modem signal if this is preferred? I don't think that would work, try it on some existing serial ports to see what they do. thanks, greg k-h