linux-kernel - Re: [PATCH 1/6] USB: serial: cp210x: fix control-characters error handling

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Date:   Mon, 5 Jul 2021 09:40:41 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Greg KH <greg@...ah.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/6] USB: serial: cp210x: fix control-characters error
 handling

On Fri, Jul 02, 2021 at 04:47:11PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Jul 02, 2021 at 03:42:22PM +0200, Johan Hovold wrote:
> > In the unlikely event that setting the software flow-control characters
> > fails the other flow-control settings should still be updated.
> > 
> > Fixes: 7748feffcd80 ("USB: serial: cp210x: add support for software flow control")
> > Cc: stable@...r.kernel.org	# 5.11
> > Signed-off-by: Johan Hovold <johan@...nel.org>
> > ---
> >  drivers/usb/serial/cp210x.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> > index 09b845d0da41..b41e2c7649fb 100644
> > --- a/drivers/usb/serial/cp210x.c
> > +++ b/drivers/usb/serial/cp210x.c
> > @@ -1217,9 +1217,7 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
> >  		chars.bXonChar = START_CHAR(tty);
> >  		chars.bXoffChar = STOP_CHAR(tty);
> >  
> > -		ret = cp210x_set_chars(port, &chars);
> > -		if (ret)
> > -			return;
> > +		cp210x_set_chars(port, &chars);
> 
> What's the odds that someone tries to add the error checking back in
> here, in a few years?  Can you put a comment here saying why you are not
> checking it?

This is just how set_termios() works and how the other requests are
handled by the driver. I can add an explicit error message here though
just like when setting the line-control register so that it doesn't look
like an oversight. The error message is currently printed by the
set_chars() helper, but I can move that out when removing the helper
later in the series.

Johan