[v2,7/8] ACPI: APEI: EINJ: Transition to the faux device interface

The APEI error injection driver does not require the creation of a
platform device. Originally, this approach was chosen for simplicity
when the driver was first implemented.

With the introduction of the lightweight faux device interface, we now
have a more appropriate alternative. Migrate the driver to utilize the
faux bus, given that the platform device it previously created was not
a real one anyway. This will simplify the code, reducing its footprint
while maintaining functionality.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: linux-acpi@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/acpi/apei/einj-core.c | 51 +++++--------------------------------------
 1 file changed, 6 insertions(+), 45 deletions(-)

On Tue, Mar 18, 2025 at 6:02 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> The APEI error injection driver does not require the creation of a
> platform device. Originally, this approach was chosen for simplicity
> when the driver was first implemented.
>
> With the introduction of the lightweight faux device interface, we now
> have a more appropriate alternative. Migrate the driver to utilize the
> faux bus, given that the platform device it previously created was not
> a real one anyway. This will simplify the code, reducing its footprint
> while maintaining functionality.
>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: linux-acpi@vger.kernel.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

This causes 0-day to complain when applied on top of 6.15-rc1:

https://lore.kernel.org/linux-acpi/202504100128.AjbVDQgK-lkp@intel.com/

> ---
>  drivers/acpi/apei/einj-core.c | 51 +++++--------------------------------------
>  1 file changed, 6 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
> index 04731a5b01faaba534bad853d0acc4c8a873a53b..5fddd01074bafab2f7b23fd7ef9f863c0856637b 100644
> --- a/drivers/acpi/apei/einj-core.c
> +++ b/drivers/acpi/apei/einj-core.c
> @@ -21,7 +21,7 @@
>  #include <linux/nmi.h>
>  #include <linux/delay.h>
>  #include <linux/mm.h>
> -#include <linux/platform_device.h>
> +#include <linux/device/faux.h>
>  #include <linux/unaligned.h>
>
>  #include "apei-internal.h"
> @@ -749,7 +749,7 @@ static int einj_check_table(struct acpi_table_einj *einj_tab)
>         return 0;
>  }
>
> -static int __init einj_probe(struct platform_device *pdev)
> +static int __init einj_probe(struct faux_device *fdev)
>  {
>         int rc;
>         acpi_status status;
> @@ -838,6 +838,8 @@ static int __init einj_probe(struct platform_device *pdev)
>
>         pr_info("Error INJection is initialized.\n");
>
> +       einj_initialized = true;
> +
>         return 0;
>
>  err_release:
> @@ -851,7 +853,7 @@ static int __init einj_probe(struct platform_device *pdev)
>         return rc;
>  }
>
> -static void __exit einj_remove(struct platform_device *pdev)
> +static void __exit einj_remove(struct faux_device *fdev)
>  {
>         struct apei_exec_context ctx;
>
> @@ -872,48 +874,7 @@ static void __exit einj_remove(struct platform_device *pdev)
>         acpi_put_table((struct acpi_table_header *)einj_tab);
>  }
>
> -static struct platform_device *einj_dev;
> -/*
> - * einj_remove() lives in .exit.text. For drivers registered via
> - * platform_driver_probe() this is ok because they cannot get unbound at
> - * runtime. So mark the driver struct with __refdata to prevent modpost
> - * triggering a section mismatch warning.
> - */
> -static struct platform_driver einj_driver __refdata = {
> -       .remove = __exit_p(einj_remove),
> -       .driver = {
> -               .name = "acpi-einj",
> -       },
> -};
> -
> -static int __init einj_init(void)
> -{
> -       struct platform_device_info einj_dev_info = {
> -               .name = "acpi-einj",
> -               .id = -1,
> -       };
> -       int rc;
> -
> -       einj_dev = platform_device_register_full(&einj_dev_info);
> -       if (IS_ERR(einj_dev))
> -               return PTR_ERR(einj_dev);
> -
> -       rc = platform_driver_probe(&einj_driver, einj_probe);
> -       einj_initialized = rc == 0;
> -
> -       return 0;
> -}
> -
> -static void __exit einj_exit(void)
> -{
> -       if (einj_initialized)
> -               platform_driver_unregister(&einj_driver);
> -
> -       platform_device_unregister(einj_dev);
> -}
> -
> -module_init(einj_init);
> -module_exit(einj_exit);
> +module_faux_driver(acpi_einj, einj_probe, __exit_p(einj_remove), true);
>
>  MODULE_AUTHOR("Huang Ying");
>  MODULE_DESCRIPTION("APEI Error INJection support");
>
> --
> 2.34.1
>
>