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

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Message-Id: <2DF972B9-EECF-44E9-93FC-74B6C3B6FFC2@goldelico.com>
Date:   Mon, 17 Feb 2020 12:07:52 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Chanwoo Choi <cw00.choi@...sung.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 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);
>> 	}
>> 
>> 	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");
>> 		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.

BR and thanks,
Nikolaus Schaller