linux-kernel - Re: [PATCH] platform/x86: intel_pmc_core: do not create a static struct device

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Date:   Thu, 24 Sep 2020 10:39:07 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rajneesh.bhardwaj@...el.com, vishwanath.somayaji@...el.com
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Rajat Jain <rajatja@...gle.com>,
        Maximilian Luz <luzmaximilian@...il.com>
Subject: Re: [PATCH] platform/x86: intel_pmc_core: do not create a static
 struct device

Hi,

On 9/23/20 8:48 PM, Greg Kroah-Hartman wrote:
> A struct device is a dynamic structure, with reference counting.
> "Tricking" the kernel to make a dynamic structure static, by working
> around the driver core release detection logic, is not nice.
> 
> Because of this, this code has been used as an example for others on
> "how to do things", which is just about the worst thing possible to have
> happen.
> 
> Fix this all up by making the platform device dynamic and providing a
> real release function.
> 
> Cc: Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>
> Cc: Vishwanath Somayaji <vishwanath.somayaji@...el.com>
> Cc: Darren Hart <dvhart@...radead.org>
> Cc: Andy Shevchenko <andy@...radead.org>
> Cc: Rajat Jain <rajatja@...gle.com>
> Cc: platform-driver-x86@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Reported-by: Maximilian Luz <luzmaximilian@...il.com>
> Fixes: b02f6a2ef0a1 ("platform/x86: intel_pmc_core: Attach using APCI HID "INT33A1"")
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans




> ---
>   drivers/platform/x86/intel_pmc_core_pltdrv.c | 26 +++++++++++++-------
>   1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel_pmc_core_pltdrv.c b/drivers/platform/x86/intel_pmc_core_pltdrv.c
> index 731281855cc8..73797680b895 100644
> --- a/drivers/platform/x86/intel_pmc_core_pltdrv.c
> +++ b/drivers/platform/x86/intel_pmc_core_pltdrv.c
> @@ -20,15 +20,10 @@
>   
>   static void intel_pmc_core_release(struct device *dev)
>   {
> -	/* Nothing to do. */
> +	kfree(dev);
>   }
>   
> -static struct platform_device pmc_core_device = {
> -	.name = "intel_pmc_core",
> -	.dev  = {
> -		.release = intel_pmc_core_release,
> -	},
> -};
> +static struct platform_device *pmc_core_device;
>   
>   /*
>    * intel_pmc_core_platform_ids is the list of platforms where we want to
> @@ -52,6 +47,8 @@ MODULE_DEVICE_TABLE(x86cpu, intel_pmc_core_platform_ids);
>   
>   static int __init pmc_core_platform_init(void)
>   {
> +	int retval;
> +
>   	/* Skip creating the platform device if ACPI already has a device */
>   	if (acpi_dev_present("INT33A1", NULL, -1))
>   		return -ENODEV;
> @@ -59,12 +56,23 @@ static int __init pmc_core_platform_init(void)
>   	if (!x86_match_cpu(intel_pmc_core_platform_ids))
>   		return -ENODEV;
>   
> -	return platform_device_register(&pmc_core_device);
> +	pmc_core_device = kzalloc(sizeof(*pmc_core_device), GFP_KERNEL);
> +	if (!pmc_core_device)
> +		return -ENOMEM;
> +
> +	pmc_core_device->name = "intel_pmc_core";
> +	pmc_core_device->dev.release = intel_pmc_core_release;
> +
> +	retval = platform_device_register(pmc_core_device);
> +	if (retval)
> +		kfree(pmc_core_device);
> +
> +	return retval;
>   }
>   
>   static void __exit pmc_core_platform_exit(void)
>   {
> -	platform_device_unregister(&pmc_core_device);
> +	platform_device_unregister(pmc_core_device);
>   }
>   
>   module_init(pmc_core_platform_init);
>