Re: [RFC PATCH] irq: add irq_domain translation infrastructure

[Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>]

Benjamin Herrenschmidt wrote:
> On Mon, 2011-06-27 at 11:00 +0200, Sebastian Andrzej Siewior wrote:
>> * Grant Likely | 2011-05-26 00:54:38 [-0600]:
>>
>>> diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
>>> index 39645b6..9891cd4 100644
>>> --- a/arch/x86/kernel/devicetree.c
>>> +++ b/arch/x86/kernel/devicetree.c
>>> @@ -371,36 +321,49 @@ static struct of_ioapic_type of_ioapic_type[] =
>>> 	},
>>> };
>>>
>>> -static int ioapic_xlate(struct irq_domain *id, const u32 *intspec, u32 intsize,
>>> -			u32 *out_hwirq, u32 *out_type)
>>> +static int ioapic_dt_translate(struct irq_domain *domain,
>>> +				struct device_node *controller,
>>> +				const u32 *intspec, u32 intsize,
>>> +				irq_hw_number_t *out_hwirq, u32 *out_type)
>>> {
>>> -	struct mp_ioapic_gsi *gsi_cfg;
>>> 	struct io_apic_irq_attr attr;
>>> 	struct of_ioapic_type *it;
>>> 	u32 line, idx, type;
>>> +	int rc;
>>>
>>> -	if (intsize < 2)
>>> +	if (controller != domain->of_node)
>>> 		return -EINVAL;
>> Is there a reason not havining the (controller != domain->of_node) check
>> in irq_create_of_mapping()?
> 
> Not all domains are associated with a single OF node.
> 
> Take xics, where there can be quite a few "source controllers" which act
> as device-tree interrupt parents but there's a single global domain.

I see. No, actually I don't. xics is pseries where I don't see the .dts. 
So you are saying that we have one irq_domain but 2+ different
interrupt-parents nodes?

How do you distinguish then between two different controllers lets say
xics and a gpio based controller? This implementation calls ->dt_translate
until one controller returns 0 which looks like brute force.

xics_host_xlate() returns always zero so you would have to go for
the compatible and check it.
Every device has an interrupt-parent node. Shouldn't the code call exact 
this irq controller xlate function instead of trying them all?

>  
> Cheers,
> Ben.
> 
Sebastian