Messages in this thread | | | Date | Tue, 18 Aug 2020 12:56:09 +0300 | From | Tony Lindgren <> | Subject | Re: [PATCH] n_gsm: Fix write handling for zero bytes written |
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Hi,
* Jiri Slaby <jirislaby@kernel.org> [200818 08:24]: > On 17. 08. 20, 15:54, Tony Lindgren wrote: > > If write returns zero we currently end up removing the message > > from the queue. Instead of removing the message, we want to just > > break out of the loop just like we already do for error codes. > > When exactly does the only writer (gsmld_output) return zero for > non-zero len parameter?
I ran into this when testing with the WIP serial core PM runtime changes from Andy Shevchenko earlier. If there are also other cases where we have serial drivers return 0, I don't know about them.
Basically with the WIP serial core changes, if the open serial port is in PM runtime suspended state with it's autosuspend_delay_ms expired, we have write return 0 and just wake up the serial device on TX.
I don't think there's much anything else we can currently do there in the PM runtime suspended case as we want to get rid of the remaining pm_runtime_irq_safe() dependencies as it takes a permanent usage count on the parent device.
Regards,
Tony
> > > Signed-off-by: Tony Lindgren <tony@atomide.com> > > --- > > drivers/tty/n_gsm.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > > --- a/drivers/tty/n_gsm.c > > +++ b/drivers/tty/n_gsm.c > > @@ -691,7 +691,8 @@ static void gsm_data_kick(struct gsm_mux *gsm, struct gsm_dlci *dlci) > > print_hex_dump_bytes("gsm_data_kick: ", > > DUMP_PREFIX_OFFSET, > > gsm->txframe, len); > > - if (gsm->output(gsm, gsm->txframe, len) < 0) > > + > > + if (gsm->output(gsm, gsm->txframe, len) <= 0) > > break; > > /* FIXME: Can eliminate one SOF in many more cases */ > > gsm->tx_bytes -= msg->len; > > > > thanks, > -- > js
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