Subject: [PATCH v6 2/4] firmware: hwrng: arm_smccc_trng: Register as an SMCCC device

From: "Aneesh Kumar K.V (Arm)" <[email-masked]>
Date: Wed, 27 May 2026 15:32:31 +0530

The SMCCC TRNG interface is a firmware-provided SMCCC service rather than a
standalone platform device. Now that the SMCCC core has an SMCCC bus,
create an arm-smccc-trng device for the discovered TRNG service and convert
the hwrng driver to an SMCCC driver.

The SMCCC id table preserves module autoloading for systems where the TRNG
driver is built as a module.

The sysfs device path changes from the old smccc_trng platform-device path
to an arm-smccc device path. No known userspace dependency on the old path
was found; a Debian Code Search lookup for the existing platform-device
name/path did not find any users.

Signed-off-by: Aneesh Kumar K.V (Arm) <[email-masked]>
---
 drivers/char/hw_random/arm_smccc_trng.c | 26 ++++++++++++++-----------
 drivers/firmware/smccc/smccc.c          | 14 ++++++-------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/drivers/char/hw_random/arm_smccc_trng.c b/drivers/char/hw_random/arm_smccc_trng.c
index dcb8e7f37f25..d273e6fc7129 100644
--- a/drivers/char/hw_random/arm_smccc_trng.c
+++ b/drivers/char/hw_random/arm_smccc_trng.c
@@ -16,8 +16,8 @@
 #include <linux/device.h>
 #include <linux/hw_random.h>
 #include <linux/module.h>
-#include <linux/platform_device.h>
 #include <linux/arm-smccc.h>
+#include <linux/arm-smccc-bus.h>
 
 #ifdef CONFIG_ARM64
 #define ARM_SMCCC_TRNG_RND	ARM_SMCCC_TRNG_RND64
@@ -94,29 +94,33 @@ static int smccc_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 	return copied;
 }
 
-static int smccc_trng_probe(struct platform_device *pdev)
+static int smccc_trng_probe(struct arm_smccc_device *sdev)
 {
 	struct hwrng *trng;
 
-	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
+	trng = devm_kzalloc(&sdev->dev, sizeof(*trng), GFP_KERNEL);
 	if (!trng)
 		return -ENOMEM;
 
 	trng->name = "smccc_trng";
 	trng->read = smccc_trng_read;
 
-	return devm_hwrng_register(&pdev->dev, trng);
+	return devm_hwrng_register(&sdev->dev, trng);
 }
 
-static struct platform_driver smccc_trng_driver = {
-	.driver = {
-		.name		= "smccc_trng",
-	},
-	.probe		= smccc_trng_probe,
+static const struct arm_smccc_device_id smccc_trng_id_table[] = {
+	{ .name = "arm-smccc-trng" },
+	{}
 };
-module_platform_driver(smccc_trng_driver);
+MODULE_DEVICE_TABLE(arm_smccc, smccc_trng_id_table);
+
+static struct arm_smccc_driver smccc_trng_driver = {
+	.name	  = KBUILD_MODNAME,
+	.probe	  = smccc_trng_probe,
+	.id_table = smccc_trng_id_table,
+};
+module_arm_smccc_driver(smccc_trng_driver);
 
-MODULE_ALIAS("platform:smccc_trng");
 MODULE_AUTHOR("Andre Przywara");
 MODULE_DESCRIPTION("Arm SMCCC TRNG firmware interface support");
 MODULE_LICENSE("GPL");
diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
index 695c920a8087..6d260354d0f9 100644
--- a/drivers/firmware/smccc/smccc.c
+++ b/drivers/firmware/smccc/smccc.c
@@ -9,7 +9,6 @@
 #include <linux/init.h>
 #include <linux/arm-smccc.h>
 #include <linux/kernel.h>
-#include <linux/platform_device.h>
 #include <linux/arm-smccc-bus.h>
 #include <linux/idr.h>
 #include <linux/slab.h>
@@ -241,14 +240,13 @@ subsys_initcall(arm_smccc_bus_init);
 
 static int __init smccc_devices_init(void)
 {
-	struct platform_device *pdev;
-
 	if (smccc_trng_available) {
-		pdev = platform_device_register_simple("smccc_trng", -1,
-						       NULL, 0);
-		if (IS_ERR(pdev))
-			pr_err("smccc_trng: could not register device: %ld\n",
-			       PTR_ERR(pdev));
+		struct arm_smccc_device *sdev;
+
+		sdev = arm_smccc_device_register("arm-smccc-trng");
+		if (IS_ERR(sdev))
+			pr_err("arm-smccc-trng: could not register device: %ld\n",
+			       PTR_ERR(sdev));
 	}
 
 	return 0;
-- 
2.43.0