Re: [patch 02/33] genirq/msi: Provide struct msi_parent_ops

[Thomas Gleixner]

On Wed, Nov 16 2022 at 14:57, Jason Gunthorpe wrote:
> On Fri, Nov 11, 2022 at 02:58:14PM +0100, Thomas Gleixner wrote:
>> + * This is the most complex problem of per device MSI domains and the
>> + * underlying interrupt domain hierarchy:
>> + *
>> + * The device domain to be initialized requests the broadest feature set
>> + * possible and the underlying domain hierarchy puts restrictions on it.
>> + *
>> + * That's working perfectly fine for a strict parent->device model, but it
>> + * falls apart with a root_parent->real_parent->device chain because the
>
> This language hurt my brain :)

IKR

>> +bool msi_parent_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
>> +				  struct irq_domain *real_parent, struct msi_domain_info *info)
>
> 'real_parent' is global IRQ_DOMAIN_FLAG_MSI_PARENT of the dev for
> which we are constructing a msi_domain_info to create a child aka
> IRQ_DOMAIN_FLAG_MSI_DEVICE?
>
> 'domain' is the current step in the hierarchy as we walk up the ops
> pointers?

Yes.

> Maybe:
>
> @child_info: The MSI domain info of the IRQ_DOMAIN_FLAG_MSI_DEVICE
>              domain to be created
> @parent_domain: The IRQ_DOMAIN_FLAG_MSI_PARENT domain for the child to
>                 be created
> @domain: The domain in the hierarchy this op is being called on

Definitely better.

> And perhaps it would be a bit clearer to put the parent_domain inside
> the msi_domain_info, which is basically acting as an argument bundle
> for a future allocation call?

Maybe. Let me try.