linux-kernel - [PATCH 3/4] syscon: Wire up has-inaccessible-regs

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Message-ID: <20251129142042.344359-4-richard@nod.at>
Date: Sat, 29 Nov 2025 15:20:41 +0100
From: Richard Weinberger <richard@....at>
To: linux-kernel@...r.kernel.org
Cc: linux-omap@...r.kernel.org,
	devicetree@...r.kernel.org,
	arnd@...db.de,
	lee@...nel.org,
	dakr@...nel.org,
	rafael@...nel.org,
	gregkh@...uxfoundation.org,
	broonie@...nel.org,
	tony@...mide.com,
	rogerq@...nel.org,
	khilman@...libre.com,
	andreas@...nade.info,
	aaro.koskinen@....fi,
	conor+dt@...nel.org,
	krzk+dt@...nel.org,
	robh@...nel.org,
	Richard Weinberger <richard@....at>
Subject: [PATCH 3/4] syscon: Wire up has-inaccessible-regs

Evaluate the has-inaccessible-regs device tree property to disable
debugfs access if a register map contains dangerous/harmful registers.

Signed-off-by: Richard Weinberger <richard@....at>
---
 drivers/mfd/syscon.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index ae71a2710bed8..73fff0df3f42f 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -70,6 +70,16 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 	else if (of_property_read_bool(np, "native-endian"))
 		syscon_config.val_format_endian = REGMAP_ENDIAN_NATIVE;
 
+
+	/*
+	 * Disable debugfs access if a register map has various inaccessible
+	 * registers.
+	 * In such a case the device driver has to know exactly how and when
+	 * access is allowed but general access via userspace can cause harm.
+	 */
+	if (of_property_read_bool(np, "has-inaccessible-regs"))
+		syscon_config.debugfs_disable = true;
+
 	/*
 	 * search for reg-io-width property in DT. If it is not provided,
 	 * default to 4 bytes. regmap_init_mmio will return an error if values
-- 
2.51.0