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

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Message-ID: <76b344ea-d1fc-c080-c49a-7e18db326b64@gmail.com>
Date:   Wed, 2 May 2018 16:20:41 +0530
From:   Arvind Yadav <arvind.yadav.cs@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     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 Wednesday 02 May 2018 03:27 PM, Johan Hovold wrote:
> 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
Yes, You are coorect. It'll read gpio form gpio device node. Which means
it'll read from device tree node. without finding a valid entry. It'll 
return
an error.

~arvind