linux-kernel - Re: [PATCH RFC 03/15] drivers/base: Allocate/free platform-msi interrupts by group

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Date:   Sat, 25 Apr 2020 23:23:32 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Jiang <dave.jiang@...el.com>, vkoul@...nel.org,
        megha.dey@...ux.intel.com, maz@...nel.org, bhelgaas@...gle.com,
        rafael@...nel.org, gregkh@...uxfoundation.org, hpa@...or.com,
        alex.williamson@...hat.com, jacob.jun.pan@...el.com,
        ashok.raj@...el.com, jgg@...lanox.com, yi.l.liu@...el.com,
        baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com,
        tony.luck@...el.com, jing.lin@...el.com, dan.j.williams@...el.com,
        kwankhede@...dia.com, eric.auger@...hat.com, parav@...lanox.com
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-pci@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH RFC 03/15] drivers/base: Allocate/free platform-msi interrupts by group

Dave Jiang <dave.jiang@...el.com> writes:
> From: Megha Dey <megha.dey@...ux.intel.com>
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -135,6 +135,12 @@ enum platform_msi_type {
>  	GEN_PLAT_MSI = 1,
>  };
>  
> +struct platform_msi_group_entry {
> +	unsigned int group_id;
> +	struct list_head group_list;
> +	struct list_head entry_list;

I surely told you before that struct members want to be written tabular.

> +};
> +
>  /* Helpers to hide struct msi_desc implementation details */
>  #define msi_desc_to_dev(desc)		((desc)->dev)
>  #define dev_to_msi_list(dev)		(&(dev)->msi_list)
> @@ -145,21 +151,31 @@ enum platform_msi_type {
>  #define for_each_msi_entry_safe(desc, tmp, dev)	\
>  	list_for_each_entry_safe((desc), (tmp), dev_to_msi_list((dev)), list)
>  
> -#define dev_to_platform_msi_list(dev)	(&(dev)->platform_msi_list)
> -#define first_platform_msi_entry(dev)		\
> -	list_first_entry(dev_to_platform_msi_list((dev)), struct msi_desc, list)
> -#define for_each_platform_msi_entry(desc, dev)	\
> -	list_for_each_entry((desc), dev_to_platform_msi_list((dev)), list)
> -#define for_each_platform_msi_entry_safe(desc, tmp, dev)	\
> -	list_for_each_entry_safe((desc), (tmp), dev_to_platform_msi_list((dev)), list)
> +#define dev_to_platform_msi_group_list(dev)    (&(dev)->platform_msi_list)
> +
> +#define first_platform_msi_group_entry(dev)				\
> +	list_first_entry(dev_to_platform_msi_group_list((dev)),		\
> +			 struct platform_msi_group_entry, group_list)
>  
> -#define first_msi_entry_common(dev)	\
> -	list_first_entry_select((dev)->platform_msi_type, dev_to_platform_msi_list((dev)),	\
> +#define platform_msi_current_group_entry_list(dev)			\
> +	(&((list_last_entry(dev_to_platform_msi_group_list((dev)),	\
> +			    struct platform_msi_group_entry,		\
> +			    group_list))->entry_list))
> +
> +#define first_msi_entry_current_group(dev)				\
> +	list_first_entry_select((dev)->platform_msi_type,		\
> +				platform_msi_current_group_entry_list((dev)),	\
>  				dev_to_msi_list((dev)), struct msi_desc, list)
>  
> -#define for_each_msi_entry_common(desc, dev)	\
> -	list_for_each_entry_select((dev)->platform_msi_type, desc, dev_to_platform_msi_list((dev)), \
> -				   dev_to_msi_list((dev)), list)	\
> +#define for_each_msi_entry_current_group(desc, dev)			\
> +	list_for_each_entry_select((dev)->platform_msi_type, desc,	\
> +				   platform_msi_current_group_entry_list((dev)),\
> +				   dev_to_msi_list((dev)), list)
> +
> +#define for_each_platform_msi_entry_in_group(desc, platform_msi_group, group, dev)	\
> +	list_for_each_entry((platform_msi_group), dev_to_platform_msi_group_list((dev)), group_list)	\
> +		if (((platform_msi_group)->group_id) == (group))			\
> +			list_for_each_entry((desc), (&(platform_msi_group)->entry_list), list)

Yet more unreadable macro maze to obfuscate what the code is actually
doing. 

>  /* When an MSI domain is used as an intermediate domain */
>  int msi_domain_prepare_irqs(struct irq_domain *domain, struct device *dev,
> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
> index bc5f9e32387f..899ade394ec8 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -320,7 +320,7 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
>  	struct msi_desc *desc;
>  	int ret = 0;
>  
> -	for_each_msi_entry_common(desc, dev) {
> +	for_each_msi_entry_current_group(desc, dev) {

How is anyone supposed to figure out what the heck this means without
going through several layers of macro maze and some magic type/group
storage in struct device?

Again, function arguments exist for a reason.

Thanks,

        tglx