On Thu, Mar 12, 2015 at 08:14:40PM +0800, Yijing Wang wrote:
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)
I don't think reducing the number of arguments is a good argument for
squashing some of them together.
I don't really want to add a structure like that because it adds management
complexity for all the callers because it contains per-bridge things (bus,
parent, domain, resource, sysdata). Things like struct pci_ops and struct
pci_host_bridge_ops are much simpler because drivers can statically
allocate a single copy and use it for multiple devices.
I think it might make sense to put the struct pci_ops pointer inside struct
pci_host_bridge_ops. That would get rid of one of the arguments.
You might also be able to get rid of the "bus" argument, since the caller
should be passing an IORESOURCE_BUS resource in the resource list, and
"bus" should be the same as res->start.
Bjorn
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