Subject: Re: [RFC PATCH 07/16] PCI: Separate pci_host_bridge creation out of pci_create_root_bus()

From: Yijing Wang <[email-masked]>
Date: Wed, 19 Nov 2014 10:24:52 +0800

>> We need, some platforms pass NULL pointer as host bridge parent.
> 
> Yijing,
> 
> May I suggest a different approach here? Rather than having to pass an opaque
> pointer that gets converted by the host bridge driver back to the private
> structure, what about promoting a new style of usage, that is similar to the
> way device drivers work? Lets try to promote the embedding of the generic
> pci_host_bridge structure in the host bridge specific structure! Then we can
> access the private data doing container_of().
> 
> Something like this:
> 
> struct pci_controller {
> 	struct pci_host_bridge bridge;
> 	/* private host bridge data here */
> 	.....
> };
> 
> #define PCI_CONTROLLER(bus)	({
> 	struct pci_host_bridge *hb = to_pci_host_bridge(bus->bridge); \
> 	container_of(hb, struct pci_controller, bridge); })
> 
> 
> Then we can retrieve the host bridge structure from everywhere we have a device.

Hi Liviu, it looks good to me, because this change will involve lots platforms,
I would think more about it. Thanks for your suggestion very much! :)

Thanks!
Yijing.

> 
> Best regards,
> Liviu
> 
>>
>>>
>>>> +	host = kzalloc(sizeof(*host), GFP_KERNEL);
>>>> +	if (!host)
>>>> +		return NULL;
>>>
>>> devm_kzalloc maybe?
>>
>> I don't know much detail about devm_kzalloc(), but we have no pci host driver
>> here, and I found no devm_kzalloc() uses in core PCI code before.
>>
>>>
>>>> +	if (!resources) {
>>>> +		/* Use default IO/MEM/BUS resources*/
>>>> +		pci_add_resource(&host->windows, &ioport_resource);
>>>> +		pci_add_resource(&host->windows, &iomem_resource);
>>>> +		pci_add_resource(&host->windows, &busn_resource);
>>>> +	} else {
>>>> +		list_for_each_entry_safe(window, n, resources, list)
>>>> +			list_move_tail(&window->list, &host->windows);
>>>> +	}
>>>
>>> I think we should assume that the correct resources are passed. You
>>> could add a wrapper around this function to convert old platforms
>>> though.
>>
>> OK, I will move these code out of pci_create_host_bridge, and add a wrapper
>> to setup the default resources.
>>
>>>
>>>> +EXPORT_SYMBOL(pci_create_host_bridge);
>>>
>>> EXPORT_SYMBOL_GPL() maybe?
>>
>> OK, will update it.
>>
>>>
>>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>>>> index 8b11b38..daa7f40 100644
>>>> --- a/include/linux/pci.h
>>>> +++ b/include/linux/pci.h
>>>> @@ -402,7 +402,12 @@ struct pci_host_bridge_window {
>>>>  struct pci_host_bridge {
>>>>  	struct device dev;
>>>>  	struct pci_bus *bus;		/* root bus */
>>>> +	struct list_head list;
>>>>  	struct list_head windows;	/* pci_host_bridge_windows */
>>>> +	int busnum;
>>>
>>> The busnum should already be implied through the bus resource.
>>
>> Yes, I will consider remove it and introduce a helper function to get the root bus number, thanks!
>>
>> Thanks!
>> Yijing.
>>
>>>
>>> 	Arnd
>>>
>>> .
>>>
>>
>>
>> -- 
>> Thanks!
>> Yijing
>>
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>>
> 

-- 
Thanks!
Yijing