[PATCH 4/4] tty/serial: sh-sci: remove uneeded IS_ERR_OR_NULL calls
Uwe Kleine-König
u.kleine-koenig at pengutronix.de
Fri Mar 3 11:44:14 PST 2017
Hello Geert,
On Fri, Mar 03, 2017 at 08:21:05PM +0100, Geert Uytterhoeven wrote:
> > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> > index 91e7dddbf72c..2f4cdd4e7b4f 100644
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -3022,7 +3022,7 @@ static int sci_probe_single(struct platform_device *dev,
> > return ret;
> >
> > sciport->gpios = mctrl_gpio_init(&sciport->port, 0);
> > - if (IS_ERR(sciport->gpios) && PTR_ERR(sciport->gpios) != -ENOSYS)
> > + if (IS_ERR(sciport->gpios))
> > return PTR_ERR(sciport->gpios);
>
> Now the sh-sci driver fails to probe on legacy platforms where GPIOLIB=n.
> The check for -ENOSYS made it succeed before.
That's right, intended and the only option that's save (for some
definition of save; the obvious downside is that there is no
/dev/tty$whatever for you).
Ignoring -ENOSYS is only ok if your device doesn't have a cts-gpio. If
it has, ignoring -ENOSYS hides bugs because the driver sends data while
it shouldn't or cannot signal the other side that it should stop (or
start) a transmission.
So the options are:
- enable GPIOLIB (maybe enforce that by letting the driver select it)
- introduce a CONFIG_HALFGPIOLIB that makes gpiod_get_optional and
mctrl_gpio_init return only then -ENOSYS if there is a gpio specified
and NULL otherwise.
> > Then mctrl_gpio_to_gpiod isn't called. I don't have a machine to test
> > this, but I think currently this makes the machine barf to continue
> > here because with sciport->gpios = ERR_PTR(-ENOSYS) calling
> >
> > mctrl_gpio_to_gpiod(sciport->gpios, ...)
> >
> > is a bad idea.
>
> If sciport->gpios == ERR_PTR(-ENOSYS), CONFIG_GPIOLIB is not enabled, the
> feature is not available, and mctrl_gpio_to_gpiod() will not
> dereference the error
> pointer.
Ah, makes sense.
> >> Perhaps mctrl_gpio_to_gpiod() should always return NULL if !CONFIG_GPIOLIB?
> >
> > No, mctrl_gpio_to_gpiod is right. You are only supposed to call it if
> > mctrl_gpio_init succeeded.
>
> Then I have to add checks for sciport->gpios == ERR_PTR(-ENOSYS)...
No, ignoring -ENOSYS is wrong.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
More information about the linux-arm-kernel
mailing list