linux-kernel - Re: [PATCH 5/8] platform: add platform_get_device_match

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Message-ID: <20240817161859.3fef7a8d@jic23-huawei>
Date: Sat, 17 Aug 2024 16:18:59 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Guillaume Stols <gstols@...libre.com>
Cc: Uwe Kleine-König <ukleinek@...nel.org>, Lars-Peter
 Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Jonathan Corbet <corbet@....net>,
 linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-fbdev@...r.kernel.org, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
 aardelean@...libre.com
Subject: Re: [PATCH 5/8] platform: add platform_get_device_match_data()
 helper

On Thu, 15 Aug 2024 12:11:59 +0000
Guillaume Stols <gstols@...libre.com> wrote:

> Inspired from spi_get_device_match_data() helper: if OF or ACPI driver
> data is available, platform_get_device_id will return NULL because
> platform_match_id is not called, and pdev->id_entry is never populated.
> This helper function checks if match data is available, and otherwise
> returns the ID table data.

Likely no one will read the patch description but for these it's worth
some scary text to point out that the driver_data must be a pointer.
If people use an enum we need to do a dance to avoid the value 0.

We get quite a few buggy conversions of i2c/spi drivers as a result
of that little gotcha.

Otherwise this seems like a sensible addition to me.

Potentially worth pulling out as a precursor series with a few examples
of how it saves on repeating this same code block in a bunch
of existing drivers.  Up to GregKH I think for how he'd like this
(assuming he approves!)

Jonathan

> 
> Signed-off-by: Guillaume Stols <gstols@...libre.com>
> ---
>  drivers/base/platform.c         | 12 ++++++++++++
>  include/linux/platform_device.h |  1 +
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 4c3ee6521ba5..26e9a026eb05 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1090,6 +1090,18 @@ static const struct platform_device_id *platform_match_id(
>  	return NULL;
>  }
>  
> +const void *platform_get_device_match_data(const struct platform_device *pdev)
> +{
> +	const struct platform_device_id *match;
> +
> +	match = device_get_match_data(&pdev->dev);
> +	if (match)
> +		return match;
> +
> +	return (const void *)platform_get_device_id(pdev)->driver_data;
> +}
> +EXPORT_SYMBOL_GPL(platform_get_device_match_data);
> +
>  #ifdef CONFIG_PM_SLEEP
>  
>  static int platform_legacy_suspend(struct device *dev, pm_message_t mesg)
> diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> index d422db6eec63..e2cc09ecc447 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -45,6 +45,7 @@ struct platform_device {
>  };
>  
>  #define platform_get_device_id(pdev)	((pdev)->id_entry)
> +extern const void *platform_get_device_match_data(const struct platform_device *pdev);
>  
>  #define dev_is_platform(dev) ((dev)->bus == &platform_bus_type)
>  #define to_platform_device(x) container_of((x), struct platform_device, dev)
>