Hi Thomas,

On 19/07/2016 16:38, Thomas Gleixner wrote:

On Tue, 19 Jul 2016, Eric Auger wrote:

quoted

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.

quoted

+/**
+ * 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?

I am confused by this comment. I was told in the past that it was better
to put the comments in the API header. On your side do you want me to
move all function kernel-doc comments to the implementation.

Looking at kernel-doc-nano-HOWTO.txt, I was not able to find any
indication about the best choice.

I will now run the kernel-doc script to check the conformance of my
comments.

Thank you for your patience!

Best Regards

Eric

quoted

+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? 

quoted

+{
+	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.

quoted

+{
+	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

quoted

+		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