Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()

Jason Gunthorpe
2021-12-01T18:47:30Z

On Wed, Dec 01, 2021 at 07:37:32PM +0100, Thomas Gleixner wrote:
> On Wed, Dec 01 2021 at 11:11, Jason Gunthorpe wrote:
> > On Wed, Dec 01, 2021 at 03:52:02PM +0100, Thomas Gleixner wrote:
> >> So we really can go and create a MSI irqdomain and stick the pointer
> >> into stdev->dev.irqdomain. The parent domain of this irqdomain is
> >>
> >> stdev->pdev.dev.irqdomain->parent
> >
> > It can work (pending some solution to the iommu stuff), but IMHO it is
> > strange/hacky to put HW objects like irqdomain on what is a character
> > struct device with a set major/minor in dev->devt and associated
> > struct cdev.
> >
> > Conceptually it makes no sense to me, cdevs are software constructs,
> > they should never go into HW areas..
>
> I picked that because it _is_ already used to establish the connection
> to the switchtec_class NTB driver which is beyond the usual cdev muck.

IMHO that is also a misuse. These days two drivers should be hooked
together using an aux device, not a cdev and the obscure
class_interface stuff. Aux device supports auto probing and module
auto loading for instance.

An interrupt on an aux device is at least somewhat conceptually
parallel to an interrupt on a mdev as both are usually representing
some slice of a device.

Thanks,
Jason