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From: Marc Zyngier <maz@kernel.org>
To: "Marek Behún" <kabel@kernel.org>
Cc: "Pali Rohár" <pali@kernel.org>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Russell King" <rmk+kernel@armlinux.org.uk>,
	"Remi Pommarel" <repk@triplefau.lt>, Xogium <contact@xogium.me>,
	"Tomasz Maciej Nowak" <tmn505@gmail.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 15/42] PCI: aardvark: Change name of INTx irq_chip to advk-INT
Date: Mon, 24 May 2021 16:14:59 +0100	[thread overview]
Message-ID: <87h7isw4cs.wl-maz@kernel.org> (raw)
In-Reply-To: <20210524163651.430e5497@thinkpad>

On Mon, 24 May 2021 15:36:51 +0100,
Marek Behún <kabel@kernel.org> wrote:
> 
> On Fri, 07 May 2021 10:08:18 +0100
> Marc Zyngier <maz@kernel.org> wrote:
> 
> > On Thu, 06 May 2021 16:31:26 +0100,
> > Pali Rohár <pali@kernel.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?

No, this is final. Show anything in /proc/*, maintain it forever. We
already went there with the bogomips crap showing up in
/proc/cpuinfo. There is no way you can know what userspace does, and
the best course of action is not to change things for some dubious
value of "nicer" or "less confusing".

> 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...

No, you would have to keep the *exact same output*. Userspace doesn't
know about drivers, and expect things in /proc to be stable.

Frankly, there are more important things to do than to worry about the
shape of /proc/interrupts. And if we could change it, I'd simply get
rid of it (you really should look at it on a system that has ~200
CPUs...).

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-05-24 15:23 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 15:31 [PATCH 00/42] PCI: aardvark: Various driver fixes Pali Rohár
2021-05-06 15:31 ` [PATCH 01/42] PCI: aardvark: Fix kernel panic during PIO transfer Pali Rohár
2021-05-19  8:06   ` Pali Rohár
2021-05-06 15:31 ` [PATCH 02/42] PCI: aardvark: Fix checking for PIO Non-posted Request Pali Rohár
2021-05-06 15:31 ` [PATCH 03/42] PCI: aardvark: Fix checking for PIO status Pali Rohár
2021-05-06 15:31 ` [PATCH 04/42] PCI: aardvark: Increase polling delay to 1.5s while waiting for PIO response Pali Rohár
2021-05-06 15:31 ` [PATCH 05/42] PCI: pci-bridge-emul: Add PCIe Root Capabilities Register Pali Rohár
2021-05-06 23:10   ` Bjorn Helgaas
2021-05-07 14:40     ` Pali Rohár
2021-05-07 16:41       ` Bjorn Helgaas
2021-05-06 15:31 ` [PATCH 06/42] PCI: aardvark: Fix reporting CRS Software Visibility on emulated bridge Pali Rohár
2021-05-07 13:03   ` Bjorn Helgaas
2021-05-07 15:25     ` Pali Rohár
2021-05-07 15:33     ` Pali Rohár
2021-05-06 15:31 ` [PATCH 07/42] PCI: aardvark: Fix link training Pali Rohár
2021-05-06 15:31 ` [PATCH 08/42] PCI: Add PCI_EXP_DEVCTL_PAYLOAD_* macros Pali Rohár
2021-05-06 15:31 ` [PATCH 09/42] PCI: aardvark: Fix PCIe Max Payload Size setting Pali Rohár
2021-05-06 15:31 ` [PATCH 10/42] PCI: aardvark: Implement workaround for the readback value of VEND_ID Pali Rohár
2021-05-06 15:31 ` [PATCH 11/42] PCI: aardvark: Do not touch status bits of masked interrupts in interrupt handler Pali Rohár
2021-05-06 15:31 ` [PATCH 12/42] PCI: aardvark: Check for virq mapping when processing INTx IRQ Pali Rohár
2021-05-07  9:15   ` Marc Zyngier
2021-06-04 16:24     ` Pali Rohár
2021-06-04 16:29       ` Marc Zyngier
2021-05-06 15:31 ` [PATCH 13/42] PCI: aardvark: Remove irq_mask_ack callback for INTx interrupts Pali Rohár
2021-05-07  9:16   ` Marc Zyngier
2021-05-06 15:31 ` [PATCH 14/42] PCI: aardvark: Don't mask irq when mapping Pali Rohár
2021-05-07  9:20   ` Marc Zyngier
2021-05-07  9:27     ` Pali Rohár
2021-05-06 15:31 ` [PATCH 15/42] PCI: aardvark: Change name of INTx irq_chip to advk-INT Pali Rohár
2021-05-07  9:08   ` Marc Zyngier
2021-05-24 14:36     ` Marek Behún
2021-05-24 15:14       ` Marc Zyngier [this message]
2021-05-06 15:31 ` [PATCH 16/42] PCI: aardvark: Remove unneeded goto Pali Rohár
2021-05-06 15:31 ` [PATCH 17/42] PCI: aardvark: Fix support for MSI interrupts Pali Rohár
2021-05-07 10:16   ` Marc Zyngier
2021-05-07 14:44     ` Pali Rohár
2021-05-07 16:24       ` Marc Zyngier
2021-06-04 16:02         ` Pali Rohár
2021-06-04 16:22           ` Marc Zyngier
2021-05-06 15:31 ` [PATCH 18/42] PCI: aardvark: Correctly clear and unmask all " Pali Rohár
2021-05-07 10:19   ` Marc Zyngier
2021-05-07 10:21     ` Pali Rohár
2021-05-06 15:31 ` [PATCH 19/42] PCI: aardvark: Fix setting MSI address Pali Rohár
2021-05-07 10:25   ` Marc Zyngier
2021-05-06 15:31 ` [PATCH 20/42] PCI: aardvark: Add support for more than 32 MSI interrupts Pali Rohár
2021-07-02 21:35   ` Pali Rohár
2021-05-06 15:31 ` [PATCH 21/42] PCI: aardvark: Add support for masking " Pali Rohár
2021-05-06 15:31 ` [PATCH 22/42] PCI: aardvark: Enable MSI-X support Pali Rohár
2021-05-06 15:31 ` [PATCH 23/42] PCI: aardvark: Fix support for ERR interrupt on emulated bridge Pali Rohár
2021-05-06 15:31 ` [PATCH 24/42] PCI: aardvark: Fix support for PME " Pali Rohár
2021-05-06 15:31 ` [PATCH 25/42] PCI: aardvark: Fix support for PME requester " Pali Rohár
2021-05-06 15:31 ` [PATCH 26/42] PCI: aardvark: Fix support for bus mastering and PCI_COMMAND " Pali Rohár
2021-05-06 15:31 ` [PATCH 27/42] PCI: aardvark: Disable bus mastering and mask all interrupts when unbinding driver Pali Rohár
2021-05-06 15:31 ` [PATCH 28/42] PCI: aardvark: Free config space for emulated root bridge when unbinding driver to fix memory leak Pali Rohár
2021-05-06 15:31 ` [PATCH 29/42] PCI: aardvark: Reset PCIe card and disable PHY when unbinding driver Pali Rohár
2021-05-06 15:31 ` [PATCH 30/42] PCI: aardvark: Rewrite irq code to chained irq handler Pali Rohár
2021-05-06 15:31 ` [PATCH 31/42] PCI: aardvark: Use separate INTA interrupt for emulated root bridge Pali Rohár
2021-05-06 15:31 ` [PATCH 32/42] PCI: pci-bridge-emul: Add description for class_revision field Pali Rohár
2021-05-06 15:31 ` [PATCH 33/42] PCI: pci-bridge-emul: Add definitions for missing capabilities registers Pali Rohár
2021-05-06 15:31 ` [PATCH 34/42] PCI: aardvark: Add support for DEVCAP2, DEVCTL2, LNKCAP2 and LNKCTL2 registers on emulated bridge Pali Rohár
2021-05-06 15:31 ` [PATCH 35/42] PCI: aardvark: Add support for PCI_BRIDGE_CTL_BUS_RESET " Pali Rohár
2021-05-06 15:31 ` [PATCH 36/42] PCI: aardvark: Replace custom PCIE_CORE_ERR_CAPCTL_* macros by linux/pci_regs.h macros Pali Rohár
2021-05-06 15:31 ` [PATCH 37/42] PCI: aardvark: Replace custom PCIE_CORE_INT_* macros by linux PCI_INTERRUPT_* values Pali Rohár
2021-05-06 15:31 ` [PATCH 38/42] PCI: aardvark: Cleanup some register macros Pali Rohár
2021-05-06 15:31 ` [PATCH 39/42] PCI: aardvark: Add comments for OB_WIN_ENABLE and ADDR_WIN_DISABLE Pali Rohár
2021-05-06 15:31 ` [PATCH 40/42] PCI: pci-bridge-emul: re-arrange register tests Pali Rohár
2021-05-06 15:31 ` [PATCH 41/42] PCI: pci-bridge-emul: add support for PCIe extended capabilities Pali Rohár
2021-05-06 15:31 ` [PATCH 42/42] PCI: aardvark: Add support for Advanced Error Reporting registers on emulated bridge Pali Rohár
2021-06-03 15:16 ` [PATCH 00/42] PCI: aardvark: Various driver fixes Lorenzo Pieralisi
2021-06-03 17:02   ` Pali Rohár
2021-06-03 18:02   ` Simon Glass
2021-06-03 18:18     ` Pali Rohár
2021-06-04 14:05     ` Lorenzo Pieralisi

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