On Thu, 13 Nov 2014, Marc Zyngier wrote:
> On 12/11/14 14:46, Thomas Gleixner wrote:
> > On Wed, 12 Nov 2014, Marc Zyngier wrote:
> >> This patch introduces two optionnal fields to the msi_chip structure:
> >> - a pointer to an irq domain, describing the MSI domain associated
> >> with this msi_chip. To be populated with msi_create_irq_domain.
> >> - a domain_alloc_irqs() callback that has the same purpose as
> >> arch_setup_msi_irqs(), with the above domain as an additional
> >> parameter.
> >>
> >> If both of these fields are non-NULL, then domain_alloc_irqs() is
> >> called, bypassing the setup_irq callback. This allows the MSI driver
> >> to use the domain stacking feature without mandating core support in
> >> the architecture.
> >
> > I'd rather have the callback in the irqdomain itself. Along with a
> > callback to free the interrupts.
> >
> > AFAICT is msi_chip more or less a wrapper around the actual MSI irq
> > domain. So we rather move towards assigning irqdomain to the pci bus
> > and get rid of msi_chip instead of adding another level of obscure
> > indirection through msi_chip.
>
> I can see that putting the irq domain at the bus level makes a lot of
> sense (assuming nobody tries to have multiple MSI controllers per bus...).
That would be interesting :)
> So I'm starting with something like this:
>
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 640a1ec..07e50fc 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -41,6 +41,7 @@ struct irq_domain;
> struct of_device_id;
> struct irq_chip;
> struct irq_data;
> +struct device;
>
> /* Number of irqs reserved for a legacy isa controller */
> #define NUM_ISA_INTERRUPTS 16
> @@ -76,6 +77,10 @@ struct irq_domain_ops {
> 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);
> + int (*prepare_alloc_irqs)(struct irq_domain *d, struct device *dev,
> + unsigned int nr_irqs, int type);
> + int (*cleanup_free_irqs)(struct irq_domain *d, struct device *dev,
> + unsigned int virq, unsigned int nr_irqs);
> #endif
> };
>
> How do you see this behaving? At the moment, I have the "prepare" callback
> directly calling into pci_msi_domain_alloc_irqs() so that the irqs get
> created, but I have the nagging feeling that it's not what you want... ;-)
> The main issue I can see is that if more than one domain in the stack
> implements that, who gets to call pci_msi_domain_alloc_irqs?
>
> If we try to decouple those two, there is a problem with the creation of
> the intermediate structure (the irq_alloc_info that's in Jiang's patches),
> as this is a arch/driver/whatever specific structure.
Hard to tell. I just saw Jiangs new series arrive and I want to look
at that first before muttering nonsense.
Thanks,
tglx
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