Re: [PATCH v9 1/6] platform-msi: Add msi_remove_device_irq_domain() in platform_device_msi_free_irqs_all()

[Thomas Gleixner]

On Tue, Dec 03 2024 at 16:40, Frank Li wrote:
> On Tue, Dec 03, 2024 at 10:12:36PM +0100, Thomas Gleixner wrote:
>> Sure, but that's not a fix and not required for stable because no
>> existing driver is affected by this unless I'm missing something.
>>
>> What's the actual use case for this? You describe in great length what
>> fails, which is nice, but I'm missing the larger picture here.
>
> PCI host send a door bell to PCI endpoint, which use platform msi to
> trigger a IRQ.
>
> PCI Host side				PCI endpoint side
>
> Send "enable"  command      ->         call platform_device_msi_init_and_alloc_irqs()
> Get doorbell address        <-         send back MSI address by shared memory
> Write data to doorbell      -> 	       MSI irq handler triggered.
> Send "Disable"  command     ->	       call platform_device_msi_free_irqs_all()
>
>
> At endpoint side, need dymatic response "enable/disable" commands. Of
> course, I can call msi_remove_device_irq_domain() in my disable function.
> But I think it should be symetic in alloc/free pair functions.

No objections, but that's not a justification for a stable backport as
nothing in tree has this problem right now. You add a new use case which
requires it, so only that new use case has this dependency, no?

Thanks,

        tglx