linux-kernel - Re: [patch 21/32] NTB/msi: Convert to msi_on_each

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Message-ID: <87sfvc893n.ffs@tglx>
Date:   Wed, 01 Dec 2021 19:37:32 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Logan Gunthorpe <logang@...tatee.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>, linux-ntb@...glegroups.com,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>, x86@...nel.org
Subject: Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()

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.

Thanks,

        tglx