linux-kernel - Re: [PATCH] extcon: palmas: hide error messages if gpio returns -EPROBE

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Date:   Mon, 17 Feb 2020 20:24:04 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org,
        kernel@...a-handheld.com, linux-omap@...r.kernel.org
Subject: Re: [PATCH] extcon: palmas: hide error messages if gpio returns
 -EPROBE_DEFER

Hi,

On 2/17/20 8:07 PM, H. Nikolaus Schaller wrote:
> Hi Chanwoo Choi,
> 
>> Am 17.02.2020 um 11:15 schrieb Chanwoo Choi <cw00.choi@...sung.com>:
>>
>> Hi,
>>
>> On 2/17/20 5:55 PM, H. Nikolaus Schaller wrote:
>>> If the gpios are probed after this driver (e.g. if they
>>> come from an i2c expander) there is no need to print an
>>> error message.
>>>
>>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>>> ---
>>> drivers/extcon/extcon-palmas.c | 6 ++++--
>>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/extcon/extcon-palmas.c b/drivers/extcon/extcon-palmas.c
>>> index edc5016f46f1..9c6254c0531c 100644
>>> --- a/drivers/extcon/extcon-palmas.c
>>> +++ b/drivers/extcon/extcon-palmas.c
>>> @@ -206,14 +206,16 @@ static int palmas_usb_probe(struct platform_device *pdev)
>>> 	palmas_usb->id_gpiod = devm_gpiod_get_optional(&pdev->dev, "id",
>>> 							GPIOD_IN);
>>> 	if (IS_ERR(palmas_usb->id_gpiod)) {
>>> -		dev_err(&pdev->dev, "failed to get id gpio\n");
>>> +		if (PTR_ERR(palmas_usb->id_gpiod) != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "failed to get id gpio\n");
>>> 		return PTR_ERR(palmas_usb->id_gpiod);
>>> 	}


How about editing it ? as following:
because following suggestion reduces the one checking behavior
when return value is -EPROBE_DEFER.

	if (PTR_ERR(palmas_usb->id_gpiod) == -EPROBE_DEFER) {
		return -EPROBE_DEFER;
	} else if (IS_ERR(palmas_usb->id_gpiod)) {
		dev_err(&pdev->dev, "failed to get id gpio\n");
		return PTR_ERR(palmas_usb->id_gpiod);
	}

>>>
>>> 	palmas_usb->vbus_gpiod = devm_gpiod_get_optional(&pdev->dev, "vbus",
>>> 							GPIOD_IN);
>>> 	if (IS_ERR(palmas_usb->vbus_gpiod)) {
>>> -		dev_err(&pdev->dev, "failed to get vbus gpio\n");
>>> +		if (PTR_ERR(palmas_usb->vbus_gpiod) != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "failed to get vbus gpio\n");

ditto.

>>> 		return PTR_ERR(palmas_usb->vbus_gpiod);
>>> 	}
>>>
>>>
>>
>> Usually, gpio driver like pinctrl is very early probed
>> because almost device drivers should use gpio.
>> So, I have not any experience about this situation.
>> Do you meet this situation on any h/w board?
> 
> Yes, I have experienced that sometimes on omap5+palmas based boards.
> 
> It seems to be this:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap5-board-common.dtsi?h=v5.6-rc2#n384
> 
> The extcon_usb3 can potentially match this extcon-palmas driver at
> a moment where the palmas_gpio it is referring to has not yet been
> successfully probed. Then the palmas_gpio would return -EPROBE_DEFER.
> 
> AFAIK there is no guarantee for a specific sequence of drivers
> being probed and it is pure luck that in most cases the gpios
> are already probed.

Thanks for explaining the example.


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics