Message-ID: <CAJZ5v0h=gcEcnnWiRdLVgZgEYFg3-U=odGFPS_6odFW2+4_=YQ@mail.gmail.com>
Date:   Tue, 17 Oct 2023 16:06:43 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Michal Wilczynski <michal.wilczynski@...el.com>
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        nvdimm@...ts.linux.dev, rafael.j.wysocki@...el.com,
        andriy.shevchenko@...el.com, lenb@...nel.org,
        dan.j.williams@...el.com, vishal.l.verma@...el.com,
        ira.weiny@...el.com
Subject: Re: [PATCH v2 5/6] ACPI: NFIT: Replace acpi_driver with platform_driver

On Fri, Oct 6, 2023 at 8:33 PM Michal Wilczynski
<michal.wilczynski@...el.com> wrote:
>
> NFIT driver uses struct acpi_driver incorrectly to register itself.
> This is wrong as the instances of the ACPI devices are not meant
> to be literal devices, they're supposed to describe ACPI entry of a
> particular device.
>
> Use platform_driver instead of acpi_driver. In relevant places call
> platform devices instances pdev to make a distinction with ACPI
> devices instances.
>
> NFIT driver uses devm_*() family of functions extensively. This change
> has no impact on correct functioning of the whole devm_*() family of
> functions, since the lifecycle of the device stays the same. It is still
> being created during the enumeration, and destroyed on platform device
> removal.
>
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Michal Wilczynski <michal.wilczynski@...el.com>
> ---
>  drivers/acpi/nfit/core.c | 34 ++++++++++++++++++----------------
>  1 file changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 942b84d94078..fb0bc16fa186 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -15,6 +15,7 @@
>  #include <linux/sort.h>
>  #include <linux/io.h>
>  #include <linux/nd.h>
> +#include <linux/platform_device.h>
>  #include <asm/cacheflush.h>
>  #include <acpi/nfit.h>
>  #include "intel.h"
> @@ -98,7 +99,7 @@ static struct acpi_device *to_acpi_dev(struct acpi_nfit_desc *acpi_desc)
>                         || strcmp(nd_desc->provider_name, "ACPI.NFIT") != 0)
>                 return NULL;
>
> -       return to_acpi_device(acpi_desc->dev);
> +       return ACPI_COMPANION(acpi_desc->dev);
>  }
>
>  static int xlat_bus_status(void *buf, unsigned int cmd, u32 status)
> @@ -3284,11 +3285,11 @@ static void acpi_nfit_put_table(void *table)
>
>  static void acpi_nfit_notify(acpi_handle handle, u32 event, void *data)
>  {
> -       struct acpi_device *adev = data;
> +       struct device *dev = data;
>
> -       device_lock(&adev->dev);
> -       __acpi_nfit_notify(&adev->dev, handle, event);
> -       device_unlock(&adev->dev);
> +       device_lock(dev);
> +       __acpi_nfit_notify(dev, handle, event);
> +       device_unlock(dev);

Careful here.

The ACPI device locking is changed to platform device locking without
a word of explanation in the changelog.

Do you actually know what the role of the locking around
__acpi_nfit_notify() is and whether or not it can be replaced with
platform device locking safely?

>  }
>
>  static void acpi_nfit_remove_notify_handler(void *data)
> @@ -3329,11 +3330,12 @@ void acpi_nfit_shutdown(void *data)
>  }
>  EXPORT_SYMBOL_GPL(acpi_nfit_shutdown);
>
> -static int acpi_nfit_add(struct acpi_device *adev)
> +static int acpi_nfit_probe(struct platform_device *pdev)
>  {
>         struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
>         struct acpi_nfit_desc *acpi_desc;
> -       struct device *dev = &adev->dev;
> +       struct device *dev = &pdev->dev;
> +       struct acpi_device *adev = ACPI_COMPANION(dev);
>         struct acpi_table_header *tbl;
>         acpi_status status = AE_OK;
>         acpi_size sz;
> @@ -3360,7 +3362,7 @@ static int acpi_nfit_add(struct acpi_device *adev)
>         acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
>         if (!acpi_desc)
>                 return -ENOMEM;
> -       acpi_nfit_desc_init(acpi_desc, &adev->dev);
> +       acpi_nfit_desc_init(acpi_desc, dev);

You seem to think that replacing adev->dev with pdev->dev everywhere
in this driver will work,

Have you verified that in any way?  If so, then how?

>
>         /* Save the acpi header for exporting the revision via sysfs */
>         acpi_desc->acpi_header = *tbl;
> @@ -3391,7 +3393,7 @@ static int acpi_nfit_add(struct acpi_device *adev)
>                 return rc;
>
>         rc = acpi_dev_install_notify_handler(adev, ACPI_DEVICE_NOTIFY,
> -                                            acpi_nfit_notify, adev);
> +                                            acpi_nfit_notify, dev);
>         if (rc)
>                 return rc;
>
> @@ -3475,11 +3477,11 @@ static const struct acpi_device_id acpi_nfit_ids[] = {
>  };
>  MODULE_DEVICE_TABLE(acpi, acpi_nfit_ids);
>
> -static struct acpi_driver acpi_nfit_driver = {
> -       .name = KBUILD_MODNAME,
> -       .ids = acpi_nfit_ids,
> -       .ops = {
> -               .add = acpi_nfit_add,
> +static struct platform_driver acpi_nfit_driver = {
> +       .probe = acpi_nfit_probe,
> +       .driver = {
> +               .name = KBUILD_MODNAME,
> +               .acpi_match_table = acpi_nfit_ids,
>         },
>  };
>
> @@ -3517,7 +3519,7 @@ static __init int nfit_init(void)
>                 return -ENOMEM;
>
>         nfit_mce_register();
> -       ret = acpi_bus_register_driver(&acpi_nfit_driver);
> +       ret = platform_driver_register(&acpi_nfit_driver);
>         if (ret) {
>                 nfit_mce_unregister();
>                 destroy_workqueue(nfit_wq);
> @@ -3530,7 +3532,7 @@ static __init int nfit_init(void)
>  static __exit void nfit_exit(void)
>  {
>         nfit_mce_unregister();
> -       acpi_bus_unregister_driver(&acpi_nfit_driver);
> +       platform_driver_unregister(&acpi_nfit_driver);
>         destroy_workqueue(nfit_wq);
>         WARN_ON(!list_empty(&acpi_descs));
>  }
> --

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