Re: [PATCH v1 4/8] ACPI: x86/rtc-cmos: Use platform device for driver binding

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 23/02/2026 16:30:21+0100, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> Modify the rtc-cmos driver to bind to a platform device on systems with
> ACPI via acpi_match_table and advertise the CMOST RTC ACPI device IDs
> for driver auto-loading.  Note that adding the requisite device IDs to
> it and exposing them via MODULE_DEVICE_TABLE() is sufficient for this
> purpose.
> 
> Since the ACPI device IDs in question are the same as for the CMOS RTC
> ACPI scan handler, put them into a common header file and use the
> definition from there in both places.
> 
> Additionally, to prevent a PNP device from being created for the CMOS
> RTC if a platform one is present already, make is_cmos_rtc_device()
> check cmos_rtc_platform_device_present introduced previously.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
>  drivers/acpi/acpi_pnp.c     |  2 +-
>  drivers/acpi/x86/cmos_rtc.c |  5 +----
>  drivers/rtc/rtc-cmos.c      | 10 ++++++++++
>  include/linux/acpi.h        |  6 ++++++
>  4 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/acpi/acpi_pnp.c b/drivers/acpi/acpi_pnp.c
> index 85d9f78619a2..4ad8f56d1a5d 100644
> --- a/drivers/acpi/acpi_pnp.c
> +++ b/drivers/acpi/acpi_pnp.c
> @@ -368,7 +368,7 @@ static int is_cmos_rtc_device(struct acpi_device *adev)
>  		{ "PNP0B02" },
>  		{""},
>  	};
> -	return !acpi_match_device_ids(adev, ids);
> +	return !cmos_rtc_platform_device_present && !acpi_match_device_ids(adev, ids);
>  }
>  
>  bool acpi_is_pnp_device(struct acpi_device *adev)
> diff --git a/drivers/acpi/x86/cmos_rtc.c b/drivers/acpi/x86/cmos_rtc.c
> index bdd66dfd4a44..a6df5b991c96 100644
> --- a/drivers/acpi/x86/cmos_rtc.c
> +++ b/drivers/acpi/x86/cmos_rtc.c
> @@ -18,10 +18,7 @@
>  #include "../internal.h"
>  
>  static const struct acpi_device_id acpi_cmos_rtc_ids[] = {
> -	{ "PNP0B00" },
> -	{ "PNP0B01" },
> -	{ "PNP0B02" },
> -	{}
> +	ACPI_CMOS_RTC_IDS
>  };
>  
>  bool cmos_rtc_platform_device_present;
> diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
> index 0743c6acd6e2..7457f42fd6f0 100644
> --- a/drivers/rtc/rtc-cmos.c
> +++ b/drivers/rtc/rtc-cmos.c
> @@ -27,6 +27,7 @@
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> +#include <linux/acpi.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -1476,6 +1477,14 @@ static __init void cmos_of_init(struct platform_device *pdev)
>  #else
>  static inline void cmos_of_init(struct platform_device *pdev) {}
>  #endif
> +
> +#ifdef CONFIG_ACPI
> +static const struct acpi_device_id acpi_cmos_rtc_ids[] = {
> +	ACPI_CMOS_RTC_IDS
> +};
> +MODULE_DEVICE_TABLE(acpi, acpi_cmos_rtc_ids);
> +#endif
> +
>  /*----------------------------------------------------------------*/
>  
>  /* Platform setup should have set up an RTC device, when PNP is
> @@ -1530,6 +1539,7 @@ static struct platform_driver cmos_platform_driver = {
>  		.name		= driver_name,
>  		.pm		= &cmos_pm_ops,
>  		.of_match_table = of_match_ptr(of_cmos_match),
> +		.acpi_match_table = ACPI_PTR(acpi_cmos_rtc_ids),
>  	}
>  };
>  
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 2bdb801cee01..5ecdcdaf31aa 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -791,6 +791,12 @@ const char *acpi_get_subsystem_id(acpi_handle handle);
>  int acpi_mrrm_max_mem_region(void);
>  #endif
>  
> +#define ACPI_CMOS_RTC_IDS	\
> +	{ "PNP0B00", },		\
> +	{ "PNP0B01", },		\
> +	{ "PNP0B02", },		\
> +	{ "", }
> +
>  extern bool cmos_rtc_platform_device_present;
>  
>  #else	/* !CONFIG_ACPI */
> -- 
> 2.51.0
> 
> 
> 
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com