Subject: [PATCH v6 06/30] PCI: Combine PCI domain and bus number in u32 arg

From: [email-masked] (Yijing Wang)
Date: Thu, 12 Mar 2015 20:14:40 +0800

On 2015/3/12 9:29, Bjorn Helgaas wrote:
> On Mon, Mar 09, 2015 at 10:34:03AM +0800, Yijing Wang wrote:
>> Currently, we use int type for bus number in
>> pci_create_root_bus(), pci_scan_root_bus() and
>> pci_scan_bus_legacy. Because PCI bus number
>> always <= 255, so we could change the bus number
>> argument type to u32, and combine PCI domain and
>> bus number in one. 
> 
> This makes no sense.  Or rather, it only states the obvious: an 8-bit value
> and a 16-bit value will both fit in a 32-bit value.  But it doesn't say
> *why* you think it's a good idea to pass a single value that contains both
> domain and bus numbers.  The obvious thing is to pass two separate values,
> and you don't say why passing a single combined value is better.

Sorry for my poor description for this patch, I combined the domain and bus, because
I think now we have too many args at pci_scan_root_bus() or other scan functions,

struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
		struct pci_ops *ops, void *sysdata, struct list_head *resources)

Now we have five args yet, plus the new introduced domain and pci_host_bridge_ops,
it will become 7.

I thought introduced a new structure which contain the necessary info to scan root bus/ host bridge,

E.g

struct pci_scan_info {
	int bus;
	struct device *parent;
	struct pci_ops *ops;
	void *sysdata;
	struct list_head *resource;
	int domain;
	struct pci_host_bridge_ops;
}

Do you like this one or keep it like now ?

pci_scan_root_bus(struct device *parent, int domain, int bus,
		struct pci_ops *ops, void *sysdata, struct list_head *resources, struct pci_host_bridge_ops *ops)

> 
> Also see whitespace mistakes below.  I get a little testy when people don't
> follow the whitespace convention of neighboring lines because if people are
> sloppy about whitespace I assume they're sloppy about the code.
> 

Sorry, I would be more careful.

>>  	int error;
>> @@ -1901,6 +1901,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>>  	resource_size_t offset;
>>  	char bus_addr[64];
>>  	char *fmt;
>> +	u8	bus = PCI_BUSNUM(db);
> 
> Whitespace botch.
> 
>>  
>>  	b = pci_alloc_bus(NULL);
>>  	if (!b)
>> @@ -1921,6 +1922,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>>  	if (!bridge)
>>  		goto err_out;
>>  
>> +	bridge->domain = PCI_DOMAIN(db);
>>  	bridge->dev.parent = parent;
>>  	bridge->dev.release = pci_release_host_bridge_dev;
>>  	dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
>> @@ -2058,7 +2060,7 @@ void pci_bus_release_busn_res(struct pci_bus *b)
>>  			res, ret ? "can not be" : "is");
>>  }
>>  
>> -struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>> +struct pci_bus *pci_scan_root_bus(struct device *parent, u32 db,
>>  		struct pci_ops *ops, void *sysdata, struct list_head *resources)
>>  {
>>  	struct resource_entry *window;
>> @@ -2072,15 +2074,15 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>>  			break;
>>  		}
>>  
>> -	b = pci_create_root_bus(parent, bus, ops, sysdata, resources);
>> +	b = pci_create_root_bus(parent, db, ops, sysdata, resources);
>>  	if (!b)
>>  		return NULL;
>>  
>>  	if (!found) {
>>  		dev_info(&b->dev,
>>  		 "No busn resource found for root bus, will use [bus %02x-ff]\n",
>> -			bus);
>> -		pci_bus_insert_busn_res(b, bus, 255);
>> +			PCI_BUSNUM(db));
>> +		pci_bus_insert_busn_res(b, PCI_BUSNUM(db), 255);
>>  	}
>>  
>>  	max = pci_scan_child_bus(b);
>> @@ -2092,7 +2094,7 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>>  }
>>  EXPORT_SYMBOL(pci_scan_root_bus);
>>  
>> -struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
>> +struct pci_bus *pci_scan_bus(u32 db, struct pci_ops *ops,
>>  					void *sysdata)
>>  {
>>  	LIST_HEAD(resources);
>> @@ -2101,7 +2103,7 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
>>  	pci_add_resource(&resources, &ioport_resource);
>>  	pci_add_resource(&resources, &iomem_resource);
>>  	pci_add_resource(&resources, &busn_resource);
>> -	b = pci_create_root_bus(NULL, bus, ops, sysdata, &resources);
>> +	b = pci_create_root_bus(NULL, db, ops, sysdata, &resources);
>>  	if (b) {
>>  		pci_scan_child_bus(b);
>>  	} else {
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 36effb8..8b3d245 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -401,6 +401,7 @@ static inline int pci_channel_offline(struct pci_dev *pdev)
>>  }
>>  
>>  struct pci_host_bridge {
>> +	u16	domain;
> 
> Please follow the existing whitespace convention, i.e., use a space, not a
> tab, between "u16 domain".
> 
>>  	struct device dev;
>>  	struct pci_bus *bus;		/* root bus */
>>  	struct list_head windows;	/* resource_entry */
>> @@ -769,14 +770,14 @@ void pcibios_bus_to_resource(struct pci_bus *bus, struct resource *res,
>>  void pcibios_scan_specific_bus(int busn);
>>  struct pci_bus *pci_find_bus(int domain, int busnr);
>>  void pci_bus_add_devices(const struct pci_bus *bus);
>> -struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops, void *sysdata);
>> -struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>> +struct pci_bus *pci_scan_bus(u32 dombus, struct pci_ops *ops, void *sysdata);
>> +struct pci_bus *pci_create_root_bus(struct device *parent, u32 dombus,
>>  				    struct pci_ops *ops, void *sysdata,
>>  				    struct list_head *resources);
>>  int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int busmax);
>>  int pci_bus_update_busn_res_end(struct pci_bus *b, int busmax);
>>  void pci_bus_release_busn_res(struct pci_bus *b);
>> -struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>> +struct pci_bus *pci_scan_root_bus(struct device *parent, u32 dombus,
>>  					     struct pci_ops *ops, void *sysdata,
>>  					     struct list_head *resources);
>>  struct pci_bus *pci_add_new_bus(struct pci_bus *parent, struct pci_dev *dev,
>> diff --git a/include/uapi/linux/pci.h b/include/uapi/linux/pci.h
>> index 3c292bc..89c6f15 100644
>> --- a/include/uapi/linux/pci.h
>> +++ b/include/uapi/linux/pci.h
>> @@ -30,6 +30,9 @@
>>  #define PCI_DEVFN(slot, func)	((((slot) & 0x1f) << 3) | ((func) & 0x07))
>>  #define PCI_SLOT(devfn)		(((devfn) >> 3) & 0x1f)
>>  #define PCI_FUNC(devfn)		((devfn) & 0x07)
>> +#define PCI_DOMAIN(db)		((db) >> 16)
>> +#define PCI_BUSNUM(db)		((db) & 0xffff)
>> +#define PCI_DOMBUS(domain, bus)		(((domain) << 16) | (bus))
>>  
>>  /* Ioctls for /proc/bus/pci/X/Y nodes. */
>>  #define PCIIOC_BASE		('P' << 24 | 'C' << 16 | 'I' << 8)
>> -- 
>> 1.7.1
>>
>> --
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> 
> .
> 

-- 
Thanks!
Yijing