linux-kernel - Re: [PATCH] pps: clients: gpio: Continue after failing to get optional ECHO pin

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Date: Mon, 3 Jun 2024 08:32:41 +0200
From: Rodolfo Giometti <giometti@...eenne.com>
To: Curtis Klein <curtis.klein@....com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pps: clients: gpio: Continue after failing to get
 optional ECHO pin

On 01/06/24 00:44, Curtis Klein wrote:
> Warn but do not fail when devm_gpiod_get_optional returns an error when
> trying to get the ECHO pin. When creating a pps-gpio device using
> platform data and GPIO lookup tables, the call to gpiod_get_optional
> will match on the unlabeled pin meant as the input when searching for
> the "echo" pin. Since it is already in use as the PPS input, it will

I'm not sure to well understand what you mean here: why the "echo" pin should be 
already in use as the PPS input?

Can you please explain better this situation with a real example?

> fail with -EBUSY. As the ECHO pin is optional, we just warn on the error
> and continue the initialization. This allows us to support devices
> created using GPIO lookup tables instead of ACPI, DT, swnode, etc.
> 
> Signed-off-by: Curtis Klein <curtis.klein@....com>
> ---
>   drivers/pps/clients/pps-gpio.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
> index 2f4b11b4dfcd..b7db4a3ee97e 100644
> --- a/drivers/pps/clients/pps-gpio.c
> +++ b/drivers/pps/clients/pps-gpio.c
> @@ -114,9 +114,12 @@ static int pps_gpio_setup(struct device *dev)
>   		device_property_read_bool(dev, "assert-falling-edge");
>   
>   	data->echo_pin = devm_gpiod_get_optional(dev, "echo", GPIOD_OUT_LOW);
> -	if (IS_ERR(data->echo_pin))
> -		return dev_err_probe(dev, PTR_ERR(data->echo_pin),
> -				     "failed to request ECHO GPIO\n");
> +	if (IS_ERR(data->echo_pin)) {
> +		dev_warn(dev, "failed to request ECHO GPIO: %ld\n",
> +			 PTR_ERR(data->echo_pin));
> +		data->echo_pin = NULL;
> +		return 0;
> +	}
>   
>   	if (!data->echo_pin)
>   		return 0;

Thanks,

Rodolfo

-- 
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