Re: [PATCH v1 7/8] rtc: cmos: Drop PNP device support

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

On 23/02/2026 16:32:29+0100, Rafael J. Wysocki wrote:
> From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> 
> Previous changes effectively prevented PNP devices from being created
> for the CMOS RTC on x86 with ACPI.
> 
> Although in principle a CMOS RTC PNP device may exist on an x86 system
> without ACPI (that is, an x86 system where there is no ACPI at all, not
> one booted with ACPI disabled), such systems were there in the field ~30
> years ago and most likely they would not be able to run a contemporary
> Linux kernel.
> 
> For the above reasons, drop the PNP device support from the rtc-cmos
> driver.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
>  drivers/rtc/rtc-cmos.c | 113 +++--------------------------------------
>  1 file changed, 8 insertions(+), 105 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
> index 7457f42fd6f0..9ac5bab846c1 100644
> --- a/drivers/rtc/rtc-cmos.c
> +++ b/drivers/rtc/rtc-cmos.c
> @@ -1370,85 +1370,6 @@ static int __maybe_unused cmos_resume(struct device *dev)
>  
>  static SIMPLE_DEV_PM_OPS(cmos_pm_ops, cmos_suspend, cmos_resume);
>  
> -/*----------------------------------------------------------------*/
> -
> -/* On non-x86 systems, a "CMOS" RTC lives most naturally on platform_bus.
> - * ACPI systems always list these as PNPACPI devices, and pre-ACPI PCs
> - * probably list them in similar PNPBIOS tables; so PNP is more common.
> - *
> - * We don't use legacy "poke at the hardware" probing.  Ancient PCs that
> - * predate even PNPBIOS should set up platform_bus devices.
> - */
> -
> -#ifdef	CONFIG_PNP
> -
> -#include <linux/pnp.h>
> -
> -static int cmos_pnp_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
> -{
> -	int irq;
> -
> -	if (pnp_port_start(pnp, 0) == 0x70 && !pnp_irq_valid(pnp, 0)) {
> -		irq = 0;
> -#ifdef CONFIG_X86
> -		/* Some machines contain a PNP entry for the RTC, but
> -		 * don't define the IRQ. It should always be safe to
> -		 * hardcode it on systems with a legacy PIC.
> -		 */
> -		if (nr_legacy_irqs())
> -			irq = RTC_IRQ;
> -#endif
> -	} else {
> -		irq = pnp_irq(pnp, 0);
> -	}
> -
> -	return cmos_do_probe(&pnp->dev, pnp_get_resource(pnp, IORESOURCE_IO, 0), irq);
> -}
> -
> -static void cmos_pnp_remove(struct pnp_dev *pnp)
> -{
> -	cmos_do_remove(&pnp->dev);
> -}
> -
> -static void cmos_pnp_shutdown(struct pnp_dev *pnp)
> -{
> -	struct device *dev = &pnp->dev;
> -	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
> -
> -	if (system_state == SYSTEM_POWER_OFF) {
> -		int retval = cmos_poweroff(dev);
> -
> -		if (cmos_aie_poweroff(dev) < 0 && !retval)
> -			return;
> -	}
> -
> -	cmos_do_shutdown(cmos->irq);
> -}
> -
> -static const struct pnp_device_id rtc_ids[] = {
> -	{ .id = "PNP0b00", },
> -	{ .id = "PNP0b01", },
> -	{ .id = "PNP0b02", },
> -	{ },
> -};
> -MODULE_DEVICE_TABLE(pnp, rtc_ids);
> -
> -static struct pnp_driver cmos_pnp_driver = {
> -	.name		= driver_name,
> -	.id_table	= rtc_ids,
> -	.probe		= cmos_pnp_probe,
> -	.remove		= cmos_pnp_remove,
> -	.shutdown	= cmos_pnp_shutdown,
> -
> -	/* flag ensures resume() gets called, and stops syslog spam */
> -	.flags		= PNP_DRIVER_RES_DO_NOT_CHANGE,
> -	.driver		= {
> -			.pm = &cmos_pm_ops,
> -	},
> -};
> -
> -#endif	/* CONFIG_PNP */
> -
>  #ifdef CONFIG_OF
>  static const struct of_device_id of_cmos_match[] = {
>  	{
> @@ -1543,45 +1464,27 @@ static struct platform_driver cmos_platform_driver = {
>  	}
>  };
>  
> -#ifdef CONFIG_PNP
> -static bool pnp_driver_registered;
> -#endif
>  static bool platform_driver_registered;
>  
>  static int __init cmos_init(void)
>  {
> -	int retval = 0;
> +	int retval;
>  
> -#ifdef	CONFIG_PNP
> -	retval = pnp_register_driver(&cmos_pnp_driver);
> -	if (retval == 0)
> -		pnp_driver_registered = true;
> -#endif
> +	if (cmos_rtc.dev)
> +		return 0;
>  
> -	if (!cmos_rtc.dev) {
> -		retval = platform_driver_probe(&cmos_platform_driver,
> -					       cmos_platform_probe);
> -		if (retval == 0)
> -			platform_driver_registered = true;
> -	}
> +	retval = platform_driver_probe(&cmos_platform_driver, cmos_platform_probe);
> +	if (retval)
> +		return retval;
>  
> -	if (retval == 0)
> -		return 0;
> +	platform_driver_registered = true;
>  
> -#ifdef	CONFIG_PNP
> -	if (pnp_driver_registered)
> -		pnp_unregister_driver(&cmos_pnp_driver);
> -#endif
> -	return retval;
> +	return 0;
>  }
>  module_init(cmos_init);
>  
>  static void __exit cmos_exit(void)
>  {
> -#ifdef	CONFIG_PNP
> -	if (pnp_driver_registered)
> -		pnp_unregister_driver(&cmos_pnp_driver);
> -#endif
>  	if (platform_driver_registered)
>  		platform_driver_unregister(&cmos_platform_driver);
>  }
> -- 
> 2.51.0
> 
> 
> 
> 

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