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

From: Yijing Wang
Date: Thu Mar 12 2015 - 08:30:06 EST

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

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