linux-kernel - Re: [PATCH v11 05/10] genirq/msi-doorbell: msi_doorbell

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Message-ID: <alpine.DEB.2.11.1607191624400.3596@nanos>
Date:	Tue, 19 Jul 2016 16:38:33 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Eric Auger <eric.auger@...hat.com>
cc:	eric.auger.pro@...il.com, marc.zyngier@....com,
	christoffer.dall@...aro.org, andre.przywara@....com,
	robin.murphy@....com, alex.williamson@...hat.com,
	will.deacon@....com, joro@...tes.org, jason@...edaemon.net,
	linux-arm-kernel@...ts.infradead.org, drjones@...hat.com,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	pbonzini@...hat.com, linux-kernel@...r.kernel.org,
	Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
	p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
	Jean-Philippe.Brucker@....com, yehuday@...vell.com,
	Manish.Jaggi@...iumnetworks.com, robert.richter@...iumnetworks.com
Subject: Re: [PATCH v11 05/10] genirq/msi-doorbell: msi_doorbell_pages

On Tue, 19 Jul 2016, Eric Auger wrote:
> msi_doorbell_pages sum up the number of iommu pages of a given order

adding () to the function name would make it immediately clear that
msi_doorbell_pages is a function.

> +/**
> + * msi_doorbell_pages: compute the number of iommu pages of size 1 << order
> + * requested to map all the registered doorbells
> + *
> + * @order: iommu page order
> + */

Why are you adding the kernel doc to the header and not to the implementation?

> +int msi_doorbell_pages(unsigned int order);
> +
>  #else
>  
>  static inline struct irq_chip_msi_doorbell_info *
> @@ -47,6 +55,12 @@ msi_doorbell_register_global(phys_addr_t base, size_t size,
>  static inline void
>  msi_doorbell_unregister_global(struct irq_chip_msi_doorbell_info *db) {}
>  
> +static inline int
> +msi_doorbell_pages(unsigned int order)

What's the point of this line break? 

> +{
> +	return 0;
> +}
> +
>  #endif /* CONFIG_MSI_DOORBELL */
>  
>  #endif
> diff --git a/kernel/irq/msi-doorbell.c b/kernel/irq/msi-doorbell.c
> index 0ff541e..a5bde37 100644
> --- a/kernel/irq/msi-doorbell.c
> +++ b/kernel/irq/msi-doorbell.c
> @@ -60,3 +60,55 @@ void msi_doorbell_unregister_global(struct irq_chip_msi_doorbell_info *dbinfo)
>  	mutex_unlock(&irqchip_doorbell_mutex);
>  }
>  EXPORT_SYMBOL_GPL(msi_doorbell_unregister_global);
> +
> +static int compute_db_mapping_requirements(phys_addr_t addr, size_t size,
> +					   unsigned int order)
> +{
> +	phys_addr_t offset, granule;
> +	unsigned int nb_pages;
> +
> +	granule = (uint64_t)(1 << order);
> +	offset = addr & (granule - 1);
> +	size = ALIGN(size + offset, granule);
> +	nb_pages = size >> order;
> +
> +	return nb_pages;
> +}
> +
> +static int
> +compute_dbinfo_mapping_requirements(struct irq_chip_msi_doorbell_info *dbinfo,
> +				    unsigned int order)

I'm sure you can find even longer function names which require more line
breaks.

> +{
> +	int ret = 0;
> +
> +	if (!dbinfo->doorbell_is_percpu) {
> +		ret = compute_db_mapping_requirements(dbinfo->global_doorbell,
> +						      dbinfo->size, order);
> +	} else {
> +		phys_addr_t __percpu *pbase;
> +		int cpu;
> +
> +		for_each_possible_cpu(cpu) {
> +			pbase = per_cpu_ptr(dbinfo->percpu_doorbells, cpu);
> +			ret += compute_db_mapping_requirements(*pbase,
> +							       dbinfo->size,
> +							       order);
> +		}
> +	}
> +	return ret;
> +}
> +
> +int msi_doorbell_pages(unsigned int order)
> +{
> +	struct irqchip_doorbell *db;
> +	int ret = 0;
> +
> +	mutex_lock(&irqchip_doorbell_mutex);
> +	list_for_each_entry(db, &irqchip_doorbell_list, next) {

Pointless braces

> +		ret += compute_dbinfo_mapping_requirements(&db->info, order);
> +	}
> +	mutex_unlock(&irqchip_doorbell_mutex);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(msi_doorbell_pages);

So here is a general rant about your naming choices.

   struct irqchip_doorbell
   struct irq_chip_msi_doorbell_info

   struct irq_chip {
   	  ....	  *(*msi_doorbell_info);
   }

   irqchip_doorbell_mutex

   msi_doorbell_register_global
   msi_doorbell_unregister_global

   msi_doorbell_pages

This really sucks. Your public functions start sensibly with msi_doorbell.

Though what is the _global postfix for the register/unregister functions for?
Are there _private functions in the pipeline?

msi_doorbell_pages() is not telling me what it does. msi_calc_doorbell_pages()
would describe it right away.

You doorbell info structure can really do with:

    struct msi_doorbell_info;

And the wrapper struct around it is fine with:

    struct msi_doorbell;

Thanks,

	tglx