Re: [PATCH 4/5] nvme-pci: simplify nvme_setup_irqs() via .setup_affinity callback

[Ming Lei <ming.lei@redhat.com>]

On Sun, Feb 10, 2019 at 07:49:12PM +0100, Thomas Gleixner wrote:
> On Fri, 25 Jan 2019, Ming Lei wrote:
> > +static int nvme_setup_affinity(const struct irq_affinity *affd,
> > +			       struct irq_affinity_desc *masks,
> > +			       unsigned int nmasks)
> > +{
> > +	struct nvme_dev *dev = affd->priv;
> > +	int affvecs = nmasks - affd->pre_vectors - affd->post_vectors;
> > +	int curvec, usedvecs;
> > +	int i;
> > +
> > +	nvme_calc_io_queues(dev, nmasks);
> 
> So this is the only NVME specific information. Everything else can be done
> in generic code. So what you really want is:
> 
> 	struct affd {
> 		...
> +		calc_sets(struct affd *, unsigned int nvecs);
> 		...
> 	}
> 
> And sets want to be actually inside of the affinity descriptor structure:
> 
>         unsigned int num_sets;
> 	unsigned int set_vectors[MAX_SETS];
> 
> We surely can define a sensible maximum of sets for now. If that ever turns
> out to be insufficient, then struct affd might become to large for the
> stack, but for now, using e.g. 8, there is no need to do so.
> 
> So then the logic in the generic code becomes exactly the same as what you
> added to nvme_setup_affinity():
> 
> 	if (affd->calc_sets) {
> 		affd->calc_sets(affd, nvecs);
> 	} else if (!affd->num_sets) {
> 		affd->num_sets = 1;
> 		affd->set_vectors[0] = affvecs;
> 	}
> 
> 	for (i = 0; i < affd->num_sets; i++) {
> 	    ....
> 	}
> 
> See?

OK, will do this way in V2, then we can avoid drivers to abuse
the callback.

Thanks,
Ming