linux-kernel - [PATCH v2 4/5] x86/microcode: move away from using a fake platform device

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Message-ID: <2025020425-try-clicker-2267@gregkh>
Date: Tue,  4 Feb 2025 12:09:16 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Lyude Paul <lyude@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Lukas Wunner <lukas@...ner.de>,
	Mark Brown <broonie@...nel.org>,
	Maíra Canal <mairacanal@...eup.net>,
	Robin Murphy <robin.murphy@....com>,
	Simona Vetter <simona.vetter@...ll.ch>,
	Zijun Hu <quic_zijuhu@...cinc.com>,
	linux-usb@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: [PATCH v2 4/5] x86/microcode: move away from using a fake platform device

Downloading firmware needs a device to hang off of, and so a platform
device seemed like the simplest way to do this.  Now that we have a faux
device interface, use that instead as this "microcode device" is not
anything resembling a platform device at all.

Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 v2: new example patch in this series

 arch/x86/kernel/cpu/microcode/core.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index b3658d11e7b6..f42e0d1b2baa 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -17,8 +17,8 @@
 
 #define pr_fmt(fmt) "microcode: " fmt
 
-#include <linux/platform_device.h>
 #include <linux/stop_machine.h>
+#include <linux/device/faux.h>
 #include <linux/syscore_ops.h>
 #include <linux/miscdevice.h>
 #include <linux/capability.h>
@@ -238,7 +238,7 @@ static void reload_early_microcode(unsigned int cpu)
 }
 
 /* fake device for request_firmware */
-static struct platform_device	*microcode_pdev;
+static struct faux_device *microcode_fdev;
 
 #ifdef CONFIG_MICROCODE_LATE_LOADING
 /*
@@ -679,7 +679,7 @@ static int load_late_locked(void)
 	if (!setup_cpus())
 		return -EBUSY;
 
-	switch (microcode_ops->request_microcode_fw(0, &microcode_pdev->dev)) {
+	switch (microcode_ops->request_microcode_fw(0, &microcode_fdev->dev)) {
 	case UCODE_NEW:
 		return load_late_stop_cpus(false);
 	case UCODE_NEW_SAFE:
@@ -828,9 +828,9 @@ static int __init microcode_init(void)
 	if (early_data.new_rev)
 		pr_info_once("Updated early from: 0x%08x\n", early_data.old_rev);
 
-	microcode_pdev = platform_device_register_simple("microcode", -1, NULL, 0);
-	if (IS_ERR(microcode_pdev))
-		return PTR_ERR(microcode_pdev);
+	microcode_fdev = faux_device_create("microcode", NULL);
+	if (!microcode_fdev)
+		return -ENODEV;
 
 	dev_root = bus_get_dev_root(&cpu_subsys);
 	if (dev_root) {
@@ -849,7 +849,7 @@ static int __init microcode_init(void)
 	return 0;
 
  out_pdev:
-	platform_device_unregister(microcode_pdev);
+	faux_device_destroy(microcode_fdev);
 	return error;
 
 }
-- 
2.48.1