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

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Date:   Thu, 28 Oct 2021 10:28:49 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] irqchip: Provide stronger type checking for
 IRQCHIP_MATCH/IRQCHIP_DECLARE

On Wed, Oct 20, 2021 at 11:45:27AM +0100, Marc Zyngier wrote:
> 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>

This patch results in:

In file included from include/linux/irq.h:589,
                 from include/linux/of_irq.h:7,
                 from include/linux/irqchip.h:17,
                 from arch/h8300/include/asm/irq.h:5,
                 from arch/h8300/kernel/traps.c:27:
include/linux/irqdesc.h:113:33: error: 'NR_IRQS' undeclared here (not in a function)
  113 | extern struct irq_desc irq_desc[NR_IRQS];

and many similar errors when trying to build h8300 images.

Guenter

> ---
>  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
>