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

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Message-Id: <20250317-plat2faux_dev-v1-4-5fe67c085ad5@arm.com>
Date: Mon, 17 Mar 2025 10:13:16 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: linux-kernel@...r.kernel.org
Cc: Sudeep Holla <sudeep.holla@....com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Ard Biesheuvel <ardb@...nel.org>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 linux-rtc@...r.kernel.org, linux-efi@...r.kernel.org
Subject: [PATCH 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@...nel.org>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: linux-rtc@...r.kernel.org
Cc: linux-efi@...r.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@....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@...nf.org>");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("EFI RTC driver");
-MODULE_ALIAS("platform:rtc-efi");
+MODULE_ALIAS("faux:rtc-efi");

-- 
2.34.1