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....@linux.intel.com>
>>>
>> [...]
>>> /* 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.
Thanks,
Abel
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