linux-kernel - Re: [patch 00/37] genirq/msi, PCI/MSI: Spring cleaning

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Message-ID: <87y258do0o.ffs@tglx>
Date:   Sun, 28 Nov 2021 21:27:19 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     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>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        iommu@...ts.linux-foundation.org, dmaengine@...r.kernel.org,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        Vinod Koul <vkoul@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>, Sinan Kaya <okaya@...nel.org>
Subject: Re: [patch 00/37] genirq/msi, PCI/MSI: Spring cleaning - Part 2

On Sat, Nov 27 2021 at 20:39, Jason Gunthorpe wrote:
> On Sat, Nov 27, 2021 at 02:21:17AM +0100, Thomas Gleixner wrote:
>>    4) Provide a function to retrieve the Linux interrupt number for a given
>>       MSI index similar to pci_irq_vector() and cleanup all open coded
>>       variants.
>
> The msi_get_virq() sure does make a big difference.. Though it does
> highlight there is some asymmetry with how platform and PCI works here
> where PCI fills some 'struct msix_entry *'. Many drivers would be
> quite happy to just call msi_get_virq() and avoid the extra memory, so
> I think the msi_get_virq() version is good.

struct msix_entry should just go away.

90+% of the use cases fill it with a linear index range 0...N and then
use the virq entry for request_irq(). So they can just use
pci_alloc_irs_vectors_affinity() and retrieve the interrupt number via
pci_irq_vector().

The few drivers which actually use it to allocate a sparse populated MSI
index, e.g. 0, 12, 14 can be converted over to alloc vector 0 and then
use the dynamic extenstion for the rest.

Thanks,

        tglx