linux-kernel - Re: [PATCH 3/4] iio: light: max44009: add missing OF device matching

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Date:   Sat, 11 Mar 2023 12:26:19 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Marek Vasut <marek.vasut@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Robert Eshleman <bobbyeshleman@...il.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] iio: light: max44009: add missing OF device
 matching

On Sat, 11 Mar 2023 12:14:56 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> The driver currently matches only via i2c_device_id, but also has
> of_device_id table:
> 
>   drivers/iio/light/max44009.c:545:34: error: ‘max44009_of_match’ defined but not used [-Werror=unused-const-variable=]
> 
> Fixes: 6aef699a7d7e ("iio: light: add driver for MAX44009")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Don't use of_match_ptr() unless you are absolutely sure no other firmware
route will make use of the of_match_table.

In this particular case ACPI using PRP0001 is broken by that macro.

So good to set the of_match_table, but make sure to always set it
and hence you don't need the __maybe_unused.

Jonathan

> ---
>  drivers/iio/light/max44009.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/light/max44009.c b/drivers/iio/light/max44009.c
> index 3dadace09fe2..274e0b679ca2 100644
> --- a/drivers/iio/light/max44009.c
> +++ b/drivers/iio/light/max44009.c
> @@ -527,6 +527,12 @@ static int max44009_probe(struct i2c_client *client)
>  	return devm_iio_device_register(&client->dev, indio_dev);
>  }
>  
> +static const struct of_device_id max44009_of_match[] __maybe_unused = {
> +	{ .compatible = "maxim,max44009" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, max44009_of_match);
> +
>  static const struct i2c_device_id max44009_id[] = {
>  	{ "max44009", 0 },
>  	{ }
> @@ -536,18 +542,13 @@ MODULE_DEVICE_TABLE(i2c, max44009_id);
>  static struct i2c_driver max44009_driver = {
>  	.driver = {
>  		.name = MAX44009_DRV_NAME,
> +		.of_match_table = of_match_ptr(max44009_of_match),
>  	},
>  	.probe_new = max44009_probe,
>  	.id_table = max44009_id,
>  };
>  module_i2c_driver(max44009_driver);
>  
> -static const struct of_device_id max44009_of_match[] = {
> -	{ .compatible = "maxim,max44009" },
> -	{ }
> -};
> -MODULE_DEVICE_TABLE(of, max44009_of_match);
> -
>  MODULE_AUTHOR("Robert Eshleman <bobbyeshleman@...il.com>");
>  MODULE_LICENSE("GPL v2");
>  MODULE_DESCRIPTION("MAX44009 ambient light sensor driver");