linux-kernel - Re: [PATCH 15/42] PCI: aardvark: Change name of INTx irq

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Date:   Mon, 24 May 2021 16:36:51 +0200
From:   Marek Behún <kabel@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Pali Rohár <pali@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Remi Pommarel <repk@...plefau.lt>, Xogium <contact@...ium.me>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/42] PCI: aardvark: Change name of INTx irq_chip to
 advk-INT

On Fri, 07 May 2021 10:08:18 +0100
Marc Zyngier <maz@...nel.org> wrote:

> On Thu, 06 May 2021 16:31:26 +0100,
> Pali Rohár <pali@...nel.org> wrote:
> > 
> > This name is visible in /proc/interrupts file and for better reading it
> > should have at most 8 characters. Also there is no need to allocate this
> > name dynamically, since there is only one PCIe controller on Armada 37xx.
> > This aligns with how the MSI irq_chip in this driver names it's interrupt
> > ("advk-MSI").  
> 
> And *because* the name is visible in /proc/interrupts, it has become
> an ABI, and cannot be changed anymore.
> 
> We had the exact same issue with Tegra this merge window as I
> accidentally changed "Tegra" to "tegra", resulting in userspace
> programs failing find stuff in /proc/interrupts.
> 
> Please keep the name as is, no matter how ugly it is.

Hmm, I am 99% sure that for the A3720 platform this ABI change would not
affect anybody. And it does make the driver's irq names confusing.
Can't we really do anything here?

Note that there were suggestions from some people to completely remove
this driver due to the many problems it has which Pali is trying to
solve. But if the driver was removed and then later introduced again
without these problems, the new version would use the "advk-INT" IRQ
name...

Marek