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

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Message-ID: <CACK8Z6FKgtFQU+0j1PMGqEwSi_9x9v-jJFFB4k5Ok-FCjpqVMw@mail.gmail.com>
Date:   Wed, 23 Sep 2020 12:37:10 -0700
From:   Rajat Jain <rajatja@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Bhardwaj, Rajneesh" <rajneesh.bhardwaj@...el.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Maximilian Luz <luzmaximilian@...il.com>
Subject: Re: [PATCH] platform/x86: intel_pmc_core: do not create a static
 struct device

On Wed, Sep 23, 2020 at 11:47 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> 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>

Acked-by: Rajat Jain <rajatja@...gle.com>

> ---
>  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);
> --
> 2.28.0
>