Re: [patch 01/16] irqdomain: Introduce new interfaces to support hierarchy irqdomains

From: Jiang Liu
Date: Mon Nov 24 2014 - 09:14:30 EST


On 2014/11/24 22:01, Yun Wu (Abel) wrote:
> On 2014/11/24 21:13, Thomas Gleixner wrote:
>
>> On Mon, 24 Nov 2014, Yun Wu (Abel) wrote:
>>> Hi Thomas, Jiang,
>>> On 2014/11/12 21:42, Thomas Gleixner wrote:
>>>
>>>> From: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
>>>>
>>> [...]
>>>> /* Number of irqs reserved for a legacy isa controller */
>>>> #define NUM_ISA_INTERRUPTS 16
>>>> @@ -64,6 +66,16 @@ struct irq_domain_ops {
>>>> int (*xlate)(struct irq_domain *d, struct device_node *node,
>>>> const u32 *intspec, unsigned int intsize,
>>>> unsigned long *out_hwirq, unsigned int *out_type);
>>>> +
>>>> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
>>>> + /* extended V2 interfaces to support hierarchy irq_domains */
>>>> + int (*alloc)(struct irq_domain *d, unsigned int virq,
>>>> + unsigned int nr_irqs, void *arg);
>>>> + void (*free)(struct irq_domain *d, unsigned int virq,
>>>> + unsigned int nr_irqs);
>>>> + void (*activate)(struct irq_domain *d, struct irq_data *irq_data);
>>>> + void (*deactivate)(struct irq_domain *d, struct irq_data *irq_data);
>>>
>>> What's the usage of the parameter domain reference in activate/deactivate?
>>> I think the purpose of the two callbacks is to activate/deactivate the
>>> irq_data->hwirq in irq_data->domain. If so, the first parameter @domain is
>>> required to be equal to irq_data->domain (which makes @domain useless).
>>> Besides, the main responsibility of interrupt domains is to manage mappings
>>> between hardware and linux interrupt numbers, so would it be better if move
>>> the two callbacks into struct irq_chip?
>>
>> No. It's not a function of the irq_chip to activate/deactivate a
>> hierarchy. As I explained you before:
>>
>> The existing irqdomain code maps between hardware and virtual
>> interrupts and thereby activates the interrupt in hardware.
>>
>> In the hierarchical case we do not touch the hardware in the
>> allocation step, so we need to activate the allocated interrupt in the
>> hardware before we can use it. And that's clearly a domain interface
>> not a irq chip issue.
>>
>
> Makes sense, now the interrupt domain seems to be the best place.
> And when the @domain parameter can be really useful? I haven't see
> anyone using it so far.
We will use it for IOAPIC on x86, as below:
void mp_irqdomain_deactivate(struct irq_domain *domain,
struct irq_data *irq_data)
{
ioapic_mask_entry(mp_irqdomain_ioapic_idx(domain),
(int)irq_data->hwirq);
}

>From an object oriented point of view, we pass the object as the
first parameter. It's true that we could retrieve domain from
irq_data->domain instead of explicitly passing it in, but that
will cause irqdomain interfaces depends on irq_data, not sounds
a good situation:)
Thanks!
Gerry
>
> Thanks,
> Abel
>
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