RE: [PATCH v13 1/4] EINJ: Migrate to a platform driver

[Dan Williams <dan.j.williams@intel.com>]

Ben Cheatham wrote:
> Change the EINJ module to install a platform device/driver on module
> init and move the module init() and exit() functions to driver probe and
> remove. This change allows the EINJ module to load regardless of whether
> setting up EINJ succeeds, which allows dependent modules to still load
> (i.e. the CXL core).
> 
> Since EINJ may no longer be initialized when the module loads, any
> functions that are called from dependent/external modules should check
> the einj_initialized variable before calling any EINJ functions.
> 
> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
> ---
>  drivers/acpi/apei/einj.c | 46 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 43 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> index 89fb9331c611..6ea323b9d8ef 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -21,6 +21,7 @@
>  #include <linux/nmi.h>
>  #include <linux/delay.h>
>  #include <linux/mm.h>
> +#include <linux/platform_device.h>
>  #include <asm/unaligned.h>
>  
>  #include "apei-internal.h"
> @@ -137,6 +138,11 @@ static struct apei_exec_ins_type einj_ins_type[] = {
>   */
>  static DEFINE_MUTEX(einj_mutex);
>  
> +/*
> + * Exported APIs use this flag to exit early if einj_probe() failed.
> + */
> +static bool einj_initialized __ro_after_init;
> +
>  static void *einj_param;
>  
>  static void einj_exec_ctx_init(struct apei_exec_context *ctx)
> @@ -703,7 +709,7 @@ static int einj_check_table(struct acpi_table_einj *einj_tab)
>  	return 0;
>  }
>  
> -static int __init einj_init(void)
> +static int __init einj_probe(struct platform_device *pdev)
>  {
>  	int rc;
>  	acpi_status status;
> @@ -717,7 +723,7 @@ static int __init einj_init(void)
>  	status = acpi_get_table(ACPI_SIG_EINJ, 0,
>  				(struct acpi_table_header **)&einj_tab);
>  	if (status == AE_NOT_FOUND) {
> -		pr_warn("EINJ table not found.\n");
> +		pr_info("EINJ table not found.\n");

Per comment on cover letter this should be pr_debug() to hide it given
that this module is no longer only loaded manually.

>  		return -ENODEV;
>  	} else if (ACPI_FAILURE(status)) {
>  		pr_err("Failed to get EINJ table: %s\n",
> @@ -805,7 +811,7 @@ static int __init einj_init(void)
>  	return rc;
>  }
>  
> -static void __exit einj_exit(void)
> +static void __exit einj_remove(struct platform_device *pdev)
>  {
>  	struct apei_exec_context ctx;
>  
> @@ -826,6 +832,40 @@ static void __exit einj_exit(void)
>  	acpi_put_table((struct acpi_table_header *)einj_tab);
>  }
>  
> +static struct platform_device *einj_dev;
> +struct platform_driver einj_driver = {

This can be static.

> +	.remove_new = 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_OR_NULL(einj_dev))

Given that platform_device_register_full() never returns NULL, this
should be IS_ERR().

> +		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_del(einj_dev);
> +}
> +
>  module_init(einj_init);
>  module_exit(einj_exit);
>  
> -- 
> 2.34.1
>