linux-kernel - Re: [PATCH 2/4] mm: ioremap: Add arch_ioremap/iounmap

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Date:   Wed, 27 Apr 2022 22:46:05 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 2/4] mm: ioremap: Add arch_ioremap/iounmap_check()

On Wed, Apr 27, 2022 at 8:25 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Wed, 27 Apr 2022 20:20:30 +0200 Arnd Bergmann <arnd@...db.de> wrote:
> > On Wed, Apr 27, 2022 at 2:14 PM Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
> > >
> > > +bool __weak arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot)
> > > +{
> > > +       return true;
> > > +}
> > > +
> > > +bool __weak arch_iounmap_check(void __iomem *addr)
> > > +{
> > > +       return true;
> > > +}
> > > +
> >
> > I don't really like the weak functions.
>
> How come?  They work quite nicely here?

I find them rather confusing, mostly because it is less clear whether the
fallback function is used in a given configuration, or a replacement one is
present.

This is a bigger problem in some subsystems than others, and the main
place I don't like is the drivers/pci/ subsystem. A number of the uses
there should be driver specific but happen to be implemented by
architectures instead. Maybe I'm just projecting that onto other uses,
but I definitely have a bad feeling about them here.

       Arnd