linux-kernel - Re: [PATCH] PCI: rcar-host: Add static assertion to check !PCI_LOCKLESS

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Message-ID: <CAMuHMdUG_y-gb6kGd+Bgo5AQvqv009RYwVjwN5dDC0WFOuyPcg@mail.gmail.com>
Date: Mon, 22 Sep 2025 17:41:37 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-pci@...r.kernel.org, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Magnus Damm <magnus.damm@...il.com>, 
	Manivannan Sadhasivam <mani@...nel.org>, Marek Vasut <marek.vasut+renesas@...il.com>, 
	Rob Herring <robh@...nel.org>, Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, 
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] PCI: rcar-host: Add static assertion to check !PCI_LOCKLESS_CONFIG

Hi Marek,

On Mon, 22 Sept 2025 at 17:34, Marek Vasut
<marek.vasut+renesas@...lbox.org> wrote:
> This driver can not function correctly without PCIe subsystem level
> config space access serialization. In case PCI_LOCKLESS_CONFIG is
> ever enabled on ARM, complain loudly so the driver can be updated
> accordingly.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>

Thanks for your patch!

> --- a/drivers/pci/controller/pcie-rcar-host.c
> +++ b/drivers/pci/controller/pcie-rcar-host.c
> @@ -35,6 +35,14 @@
>
>  #include "pcie-rcar.h"
>
> +/*
> + * This driver can not function correctly without PCIe subsystem level
> + * config space access serialization. In case PCI_LOCKLESS_CONFIG is
> + * ever enabled on ARM, complain loudly so the driver can be updated
> + * accordingly.
> + */
> +static_assert(!IS_ENABLED(CONFIG_PCI_LOCKLESS_CONFIG));
> +
>  struct rcar_msi {
>         DECLARE_BITMAP(used, INT_PCI_MSI_NR);
>         struct irq_domain *domain;

This causes a build failure when compile-testing, e.g. x86 allmodconfig.
Using "depends on !PCI_LOCKLESS_CONFIG" instead would avoid that,
but indeed has the disadvantage that it wouldn't complain loudly when
PCI_LOCKLESS_CONFIG would ever be enabled on ARM64...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds