[PATCH 0/9] drivers: Transition to the faux device interface

[PATCH 0/9] drivers: Transition to the faux device interface

[Sudeep Holla]

Recently when debugging why one of the scmi platform device was not
showing up under /sys/devices/platform/firmware:scmi instead was
appearing directly under /sys/devices/platform, I noticed the new
faux interface /sys/devices/faux.

Looking through the discussion and the background, I got excited and
took the opportunity to clear all the platform devices under
/sys/devices/platform on the Arm Juno/FVP platforms that are really
faux devices. Only the platform devices created for the device nodes
from the DT remain under /sys/devices/platform after these changes.

All the patches are independent of each other.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
Greg Kroah-Hartman (1):
      regulator: dummy: convert to use the faux device interface

Sudeep Holla (8):
      cpuidle: psci: Transition to the faux device interface
      hwrng: arm-smccc-trng - transition to the faux device interface
      efi: Remove redundant creation of the "efivars" platform device
      rtc: efi: Transition to the faux device interface
      virt: efi_secret: Transition to the faux device interface
      ASoC: soc-utils: Transition to the faux device interface
      net: phy: fixed_phy: transition to the faux device interface
      ACPI: APEI: EINJ: Transition to the faux device interface

 drivers/acpi/apei/einj-core.c             | 32 +++++++++---------------
 drivers/char/hw_random/arm_smccc_trng.c   | 40 +++++++++++++++++++++---------
 drivers/cpuidle/cpuidle-psci.c            | 26 +++++++-------------
 drivers/firmware/efi/efi.c                | 10 --------
 drivers/firmware/smccc/smccc.c            | 21 ----------------
 drivers/net/phy/fixed_phy.c               | 16 ++++++------
 drivers/regulator/dummy.c                 | 37 +++++++---------------------
 drivers/rtc/rtc-efi.c                     | 31 ++++++++++++++++-------
 drivers/virt/coco/efi_secret/efi_secret.c | 41 ++++++++++++++++++-------------
 sound/soc/soc-utils.c                     | 34 +++++++++----------------
 10 files changed, 124 insertions(+), 164 deletions(-)
---
base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
change-id: 20250315-plat2faux_dev-8c28b35be96a
-- 
Regards,
Sudeep

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

[Sudeep Holla]

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");

-- 
2.34.1

Re: [PATCH 0/9] drivers: Transition to the faux device interface

[Greg Kroah-Hartman]

On Mon, Mar 17, 2025 at 10:13:12AM +0000, Sudeep Holla wrote:
> Recently when debugging why one of the scmi platform device was not
> showing up under /sys/devices/platform/firmware:scmi instead was
> appearing directly under /sys/devices/platform, I noticed the new
> faux interface /sys/devices/faux.
> 
> Looking through the discussion and the background, I got excited and
> took the opportunity to clear all the platform devices under
> /sys/devices/platform on the Arm Juno/FVP platforms that are really
> faux devices. Only the platform devices created for the device nodes
> from the DT remain under /sys/devices/platform after these changes.
> 
> All the patches are independent of each other.

That's great, but you need to send these all independently to each
subsystem as needed.  Having it all in one series doesn't work for any
of the maintainers of any of the subsystems.

And I'm glad to see this work happening, thanks for doing that!

greg k-h

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

[Greg Kroah-Hartman]

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.

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

[Sudeep Holla]

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.

-- 
Regards,
Sudeep

Re: [PATCH 0/9] drivers: Transition to the faux device interface

[Mark Brown]

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On Mon, Mar 17, 2025 at 10:13:12AM +0000, Sudeep Holla wrote:

> All the patches are independent of each other.

If that's the case don't send them in a series, it makes things more
complicated to apply and the CCs cause more mail.  Split independent
things up by subsystem.

[-- Attachment #2: signature.asc --]
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Re: [PATCH 0/9] drivers: Transition to the faux device interface

[Sudeep Holla]

On Mon, Mar 17, 2025 at 02:01:55PM +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 17, 2025 at 10:13:12AM +0000, Sudeep Holla wrote:
> > Recently when debugging why one of the scmi platform device was not
> > showing up under /sys/devices/platform/firmware:scmi instead was
> > appearing directly under /sys/devices/platform, I noticed the new
> > faux interface /sys/devices/faux.
> > 
> > Looking through the discussion and the background, I got excited and
> > took the opportunity to clear all the platform devices under
> > /sys/devices/platform on the Arm Juno/FVP platforms that are really
> > faux devices. Only the platform devices created for the device nodes
> > from the DT remain under /sys/devices/platform after these changes.
> > 
> > All the patches are independent of each other.
> 
> That's great, but you need to send these all independently to each
> subsystem as needed.  Having it all in one series doesn't work for any
> of the maintainers of any of the subsystems.
> 

Sure I can do that. I initially had idea of creating a macro that made
all of them depend on the macro but later dropped as I wanted to check
if that is good or a bad idea. I just asked you in the thread 2/9.

> And I'm glad to see this work happening, thanks for doing that!
> 

Thanks for adding faux interface!

-- 
Regards,
Sudeep

Re: (subset) [PATCH 0/9] drivers: Transition to the faux device interface

[Mark Brown]

On Mon, 17 Mar 2025 10:13:12 +0000, Sudeep Holla wrote:
> Recently when debugging why one of the scmi platform device was not
> showing up under /sys/devices/platform/firmware:scmi instead was
> appearing directly under /sys/devices/platform, I noticed the new
> faux interface /sys/devices/faux.
> 
> Looking through the discussion and the background, I got excited and
> took the opportunity to clear all the platform devices under
> /sys/devices/platform on the Arm Juno/FVP platforms that are really
> faux devices. Only the platform devices created for the device nodes
> from the DT remain under /sys/devices/platform after these changes.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[6/9] ASoC: soc-utils: Transition to the faux device interface
      commit: 18abb3797f1ceca97a705aa1c14cbec5c6fcab79

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark