Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> writes:
> Eric W. Biederman wrote:
>> Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> writes:
>>
>>> Eric W. Biederman wrote:
>>>> Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> writes:
>>>>
>>>>> Eric W. Biederman wrote:
>>>>>> In general a BIOS may goof or we may hotplug in a hotplug controller.
>>>>>> In either case the kernel needs to reserve resources for plugging
>>>>>> in more devices in the future instead of creating a minimal resource
>>>>>> assignment.
>>>>>>
>>>>> I think we would need the same mechanism also for PCI bus number
>>>>> assignment so that we can hot-plug devices containing bridges on
>>>>> the leaf hot-plug slots.
>>>> Yep that would be handy. I haven't had that case come up as a problem
>>>> yet.
>>>>
>>>>> (snip.)
>>>>>
>>>>>> /**
>>>>>> * pci_bus_max_busnr - returns maximum PCI bus number of given bus' children
>>>>>> * @bus: pointer to PCI bus structure to search
>>>>>> @@ -2672,6 +2678,10 @@ static int __init pci_setup(char *str)
>>>>>> strlen(str + 19));
>>>>>> } else if (!strncmp(str, "ecrc=", 5)) {
>>>>>> pcie_ecrc_get_policy(str + 5);
>>>>>> + } else if (!strncmp(str, "hpiosize=", 9)) {
>>>>>> + pci_hotplug_io_size = memparse(str + 9, &str);
>>>>>> + } else if (!strncmp(str, "hpmemsize=", 10)) {
>>>>>> + pci_hotplug_mem_size = memparse(str + 10, &str);
>>>>>> } else {
>>>>>> printk(KERN_ERR "PCI: Unknown option `%s'\n",
>>>>>> str);
>>>>> I think it would be better if we can specify the size per hotplug
>>>>> controller driver or per slot or etc.
>>>> This happens too early to do anything per driver as this all happens
>>>> before the hotplug drivers load. A per slot override seems reasonable
>>>> but I am starting with the simplest case an override of the default
>>>> allocation.
>>> Do you need to override the resource assignments by firmware
>>> at boot time?
>>
>> That has come up. Unfortunately the kernel didn't know that hardware
>> platform well enough to assign the resources correctly. So I had to
>> go back in and fix the firmware.
>>
>> I more commonly plug in pcie hotplug bridges into my pcie hotplug
>> bridges, and long before I can load a driver on them I need to assign
>> resources.
>>
>
> In addition to your requirement, I noticed another situation that
> would require the resource assignment by PCI core. I guess it
> would be required for hot-plugging PCI host bridge that contains
> some PCIe hotplug slots.
I don't quite see how that is different from my version of plugging
in pcie hotplug slots, but that certainly sounds correct. This is
also how the linux hotplug code has worked for a long time it is just
that no one has generalized this code beyond cardbus bridges before.
So we are in agreement that this is useful functionality?
Eric
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