linux-kernel - Re: [PATCH v2] staging: greybus: Use gpio_is

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Date:   Wed, 2 May 2018 11:57:37 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>
Cc:     Johan Hovold <johan@...nel.org>, hvaibhav.linux@...il.com,
        elder@...nel.org, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, greybus-dev@...ts.linaro.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH v2] staging: greybus: Use gpio_is_valid()

On Wed, May 02, 2018 at 03:15:05PM +0530, Arvind Yadav wrote:

> On Wednesday 02 May 2018 02:13 PM, Johan Hovold wrote:
> > On Sat, Apr 28, 2018 at 10:05:39AM +0530, Arvind Yadav wrote:
> >> Replace the manual validity checks for the GPIO with the
> >> gpio_is_valid().
> >>
> >> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
> >> ---
> >> chnage in v2 :
> >>               Returning invalid gpio as error instead of -ENODEV.
> >>
> >>   drivers/staging/greybus/arche-platform.c | 6 +++---
> >>   1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/staging/greybus/arche-platform.c b/drivers/staging/greybus/arche-platform.c
> >> index 83254a7..c3a7da5 100644
> >> --- a/drivers/staging/greybus/arche-platform.c
> >> +++ b/drivers/staging/greybus/arche-platform.c
> >> @@ -448,7 +448,7 @@ 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;
> >
> > I'm sorry, but I don't this change is desirable. of_get_named_gpio()
> > returns a valid gpio number or a negative errno, so there's no need to
> > use the legacy gpio_is_valid() helper here.
> >
> > If you grep for of_get_named_gpio() you'll find that some drivers indeed
> > use that helper this way, but they are in a clear minority.
> >
> > And ultimately, we want to move to using gpio descriptors anyway.
> 
> We need to check gpio validity. If we are using of_get_named_gpio() or
> not.  of_get_name_gpio() will read a device node and fetch the value.
> But it'll not check that gpio is valid or not valid.

No, I believe you're mistaken here. of_get_named_gpio() does not return
an arbitrary gpio number, unlike what you could possibly find in
legacy board files and for which the gpio_is_valid() helper made sense.

Johan