linux-kernel - [PATCH] irqchip: Provide stronger type checking for IRQCHIP_MATCH/IRQCHIP

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Date:   Wed, 20 Oct 2021 11:45:27 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Florian Fainelli <f.fainelli@...il.com>,
        Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] irqchip: Provide stronger type checking for IRQCHIP_MATCH/IRQCHIP_DECLARE

Both IRQCHIP_DECLARE() and IRQCHIP_MATCH() use an underlying of_device_id()
structure to encode the matching property and the init callback.
However, this callback is stored in as a void * pointer, which obviously
defeat any attempt at stronger type checking.

Work around this by providing a new macro that builds on top of the
__typecheck() primitive, and that can be used to warn when there is
a discrepency between the drivers and core code.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 include/linux/irqchip.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/irqchip.h b/include/linux/irqchip.h
index 67351aac65ef..5de0dfc5d64d 100644
--- a/include/linux/irqchip.h
+++ b/include/linux/irqchip.h
@@ -14,8 +14,15 @@
 #include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_irq.h>
 #include <linux/platform_device.h>
 
+/* Undefined on purpose */
+extern of_irq_init_cb_t typecheck_irq_init_cb;
+
+#define typecheck_irq_init_cb(fn)					\
+	(__typecheck(typecheck_irq_init_cb, &fn) ? fn : fn)
+
 /*
  * This macro must be used by the different irqchip drivers to declare
  * the association between their DT compatible string and their
@@ -26,14 +33,16 @@
  * @compstr: compatible string of the irqchip driver
  * @fn: initialization function
  */
-#define IRQCHIP_DECLARE(name, compat, fn) OF_DECLARE_2(irqchip, name, compat, fn)
+#define IRQCHIP_DECLARE(name, compat, fn)	\
+	OF_DECLARE_2(irqchip, name, compat, typecheck_irq_init_cb(fn))
 
 extern int platform_irqchip_probe(struct platform_device *pdev);
 
 #define IRQCHIP_PLATFORM_DRIVER_BEGIN(drv_name) \
 static const struct of_device_id drv_name##_irqchip_match_table[] = {
 
-#define IRQCHIP_MATCH(compat, fn) { .compatible = compat, .data = fn },
+#define IRQCHIP_MATCH(compat, fn) { .compatible = compat,		\
+				    .data = typecheck_irq_init_cb(fn), },
 
 #define IRQCHIP_PLATFORM_DRIVER_END(drv_name)				\
 	{},								\
-- 
2.30.2