[PATCH V2 3/6] scsi: add flag of .use_managed_irq to 'struct Scsi_Host'

[Hannes Reinecke]

On 7/6/21 9:41 AM, Ming Lei wrote:
> On Tue, Jul 06, 2021 at 07:37:19AM +0200, Christoph Hellwig wrote:
>> On Mon, Jul 05, 2021 at 05:55:49PM +0800, Ming Lei wrote:
>>> The thing is that blk_mq_pci_map_queues() is allowed to be called for
>>> non-managed irqs. Also some managed irq consumers don't use blk_mq_pci_map_queues().
>>>
>>> So this way just provides hint about managed irq uses, but we really
>>> need to get this flag set if driver uses managed irq.
>>
>> blk_mq_pci_map_queues is absolutely intended to only be used by
>> managed irqs.  I wonder if we can enforce that somehow?
> 
> It may break some scsi drivers.
> 
> And blk_mq_pci_map_queues() just calls pci_irq_get_affinity() to
> retrieve the irq's affinity, and the irq can be one non-managed irq,
> which affinity is set via either irq_set_affinity_hint() from kernel
> or /proc/irq/.
> 
But that's static, right? IE blk_mq_pci_map_queues() will be called once 
during module init; so what happens if the user changes the mapping 
later on? How will that be transferred to the driver?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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