[4/9] rtc: efi: Transition to the faux device interface

The EFI RTC 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: Ard Biesheuvel <ardb@kernel.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: linux-rtc@vger.kernel.org
Cc: linux-efi@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/firmware/efi/efi.c |  3 ---
 drivers/rtc/rtc-efi.c      | 31 ++++++++++++++++++++++---------
 2 files changed, 22 insertions(+), 12 deletions(-)

On Mon, Mar 17, 2025 at 10:13:16AM +0000, Sudeep Holla wrote:
> The EFI RTC 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: Ard Biesheuvel <ardb@kernel.org>
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: linux-rtc@vger.kernel.org
> Cc: linux-efi@vger.kernel.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/firmware/efi/efi.c |  3 ---
>  drivers/rtc/rtc-efi.c      | 31 ++++++++++++++++++++++---------
>  2 files changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index eec173cb1f398d3b4f28b42c917e50e1728dc277..18deb2d212ce6944927f5e3a9a40bb6754e7ffa9 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -427,9 +427,6 @@ static int __init efisubsys_init(void)
>  		}
>  	}
>  
> -	if (efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
> -		platform_device_register_simple("rtc-efi", 0, NULL, 0);
> -
>  	/* We register the efi directory at /sys/firmware/efi */
>  	efi_kobj = kobject_create_and_add("efi", firmware_kobj);
>  	if (!efi_kobj) {
> diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
> index fa8bf82df9488e7d1c23c058b4a3032dde74bc6e..3d21a470e8ff9777c5eeb991f3aa9170f6351930 100644
> --- a/drivers/rtc/rtc-efi.c
> +++ b/drivers/rtc/rtc-efi.c
> @@ -14,7 +14,7 @@
>  #include <linux/module.h>
>  #include <linux/stringify.h>
>  #include <linux/time.h>
> -#include <linux/platform_device.h>
> +#include <linux/device/faux.h>
>  #include <linux/rtc.h>
>  #include <linux/efi.h>
>  
> @@ -254,7 +254,7 @@ static const struct rtc_class_ops efi_rtc_ops = {
>  	.proc		= efi_procfs,
>  };
>  
> -static int __init efi_rtc_probe(struct platform_device *dev)
> +static int __init efi_rtc_probe(struct faux_device *dev)
>  {
>  	struct rtc_device *rtc;
>  	efi_time_t eft;
> @@ -268,7 +268,7 @@ static int __init efi_rtc_probe(struct platform_device *dev)
>  	if (IS_ERR(rtc))
>  		return PTR_ERR(rtc);
>  
> -	platform_set_drvdata(dev, rtc);
> +	faux_device_set_drvdata(dev, rtc);
>  
>  	rtc->ops = &efi_rtc_ops;
>  	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
> @@ -282,15 +282,28 @@ static int __init efi_rtc_probe(struct platform_device *dev)
>  	return devm_rtc_register_device(rtc);
>  }
>  
> -static struct platform_driver efi_rtc_driver = {
> -	.driver = {
> -		.name = "rtc-efi",
> -	},
> +static struct faux_device_ops efi_rtc_fdev_ops = {
> +	.probe = efi_rtc_probe,
>  };
>  
> -module_platform_driver_probe(efi_rtc_driver, efi_rtc_probe);
> +static int __init rtc_efi_init(void)
> +{
> +	struct faux_device *fdev;
> +
> +	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
> +		return 0;
> +
> +	fdev = faux_device_create("rtc-efi", NULL, &efi_rtc_fdev_ops);
> +	if (!fdev) {
> +		pr_err("rtc-efi: could not create the device\n");
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +device_initcall(rtc_efi_init);
>  
>  MODULE_AUTHOR("dann frazier <dannf@dannf.org>");
>  MODULE_LICENSE("GPL");
>  MODULE_DESCRIPTION("EFI RTC driver");
> -MODULE_ALIAS("platform:rtc-efi");
> +MODULE_ALIAS("faux:rtc-efi");

No alias please.

On Mon, Mar 17, 2025 at 02:07:00PM +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 17, 2025 at 10:13:16AM +0000, Sudeep Holla wrote:
> > The EFI RTC 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: Ard Biesheuvel <ardb@kernel.org>
> > Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> > Cc: linux-rtc@vger.kernel.org
> > Cc: linux-efi@vger.kernel.org
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  drivers/firmware/efi/efi.c |  3 ---
> >  drivers/rtc/rtc-efi.c      | 31 ++++++++++++++++++++++---------
> >  2 files changed, 22 insertions(+), 12 deletions(-)
> > 

[...]

> > -MODULE_ALIAS("platform:rtc-efi");
> > +MODULE_ALIAS("faux:rtc-efi");
> 
> No alias please.

Thanks for the review, will drop all the alias.