Re: [greybus-dev] [PATCH] staging: greybus: Use gpio_is_valid()

[arvindY]

On Friday 27 April 2018 06:32 PM, Alex Elder wrote:
> On 04/27/2018 07:50 AM, Arvind Yadav wrote:
> > On Friday 27 April 2018 05:47 PM, Alex Elder wrote:
> > > On 04/27/2018 05:52 AM, Arvind Yadav wrote:
> > > > Replace the manual validity checks for the GPIO with the
> > > > gpio_is_valid().
> > > I haven't looked through the code paths very closely, but I
> > > think that get_named_gpio() might return -EPROBE_DEFER, which
> > > would be something we want to pass to the caller.
> > Yes of_get_name_gpio() can return other error value apart from
> > -EPROBE_DEFER.
> > > So rather than returning -ENODEV and hiding the reason the
> > > call to of_get_named_gpio() failed, you should continue
> > > returning the errno it supplies (if not a valid gpio number).
> > >
> > >                      -Alex
> > I have return -ENODEV because invalid gpio pin can be positive.
> > static inline bool gpio_is_valid(int number)
> > {
> >      return number >= 0 && number < ARCH_NR_GPIOS;
> > }
> > Here if number > ARCH_NR_GPIOS then it's invalid but return value
> > will be positive.
> Your reasoning is good.  However in all three of these cases,
> the GPIO number you're checking is the value returned from
> of_get_named_gpio().  The return value is a "GPIO number to
> use with Linux generic GPIO API, or one of the errno value."
>
> So unless the API of of_get_named_gpio() changes, you can be
> sure that if the value returned is invalid, it is a negative
> errno.  (And if the API did change, the person making that
> change would be responsible for fixing all callers to ensure
> the change didn't break them.)
>
> This distinction may be why the code you're changing was only
> testing for negative, rather than using gpio_is_valid() (you'll
> see it's used elsewhere in the Greybus code--even in the same
> source files.)
>
> Anyway, changing the code to use gpio_is_valid() is fine.  But
> you should avoid obscuring the reason for the error that the
> return value from of_get_named_gpio() provides.
>
> 					-Alex

Yes, It'll be fine to return a invalid gpio as error instead of
-ENODEV. I will send an updated patch.

~arvind
> > We can return like this
> >      " return (gpio > 0) ? -ENODEV: gpio;"
> >
> > But not sure this is worth to handle this.
> >
> > ~arvind
> > > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > > > ---
> > > >    drivers/staging/greybus/arche-platform.c | 12 ++++++------
> > > >    1 file changed, 6 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/drivers/staging/greybus/arche-platform.c b/drivers/staging/greybus/arche-platform.c
> > > > index 83254a7..fc6bf60 100644
> > > > --- a/drivers/staging/greybus/arche-platform.c
> > > > +++ b/drivers/staging/greybus/arche-platform.c
> > > > @@ -448,9 +448,9 @@ static int arche_platform_probe(struct platform_device *pdev)
> > > >        arche_pdata->svc_reset_gpio = of_get_named_gpio(np,
> > > >                                "svc,reset-gpio",
> > > >                                0);
> > > > -    if (arche_pdata->svc_reset_gpio < 0) {
> > > > +    if (!gpio_is_valid(arche_pdata->svc_reset_gpio)) {
> > > >            dev_err(dev, "failed to get reset-gpio\n");
> > > > -        return arche_pdata->svc_reset_gpio;
> > > > +        return -ENODEV;
> > > >        }
> > > >        ret = devm_gpio_request(dev, arche_pdata->svc_reset_gpio, "svc-reset");
> > > >        if (ret) {
> > > > @@ -468,9 +468,9 @@ static int arche_platform_probe(struct platform_device *pdev)
> > > >        arche_pdata->svc_sysboot_gpio = of_get_named_gpio(np,
> > > >                                  "svc,sysboot-gpio",
> > > >                                  0);
> > > > -    if (arche_pdata->svc_sysboot_gpio < 0) {
> > > > +    if (!gpio_is_valid(arche_pdata->svc_sysboot_gpio)) {
> > > >            dev_err(dev, "failed to get sysboot gpio\n");
> > > > -        return arche_pdata->svc_sysboot_gpio;
> > > > +        return -ENODEV;
> > > >        }
> > > >        ret = devm_gpio_request(dev, arche_pdata->svc_sysboot_gpio, "sysboot0");
> > > >        if (ret) {
> > > > @@ -487,9 +487,9 @@ static int arche_platform_probe(struct platform_device *pdev)
> > > >        arche_pdata->svc_refclk_req = of_get_named_gpio(np,
> > > >                                "svc,refclk-req-gpio",
> > > >                                0);
> > > > -    if (arche_pdata->svc_refclk_req < 0) {
> > > > +    if (!gpio_is_valid(arche_pdata->svc_refclk_req)) {
> > > >            dev_err(dev, "failed to get svc clock-req gpio\n");
> > > > -        return arche_pdata->svc_refclk_req;
> > > > +        return -ENODEV;
> > > >        }
> > > >        ret = devm_gpio_request(dev, arche_pdata->svc_refclk_req,
> > > >                    "svc-clk-req");