Re: [PATCH v3 4/6] mm: ioremap: Add arch_ioremap/iounmap()

[Kefeng Wang]

On 2022/5/24 22:47, Arnd Bergmann wrote:
> On Tue, May 24, 2022 at 4:32 PM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > On 2022/5/24 20:37, Arnd Bergmann wrote:
> > > On Thu, May 19, 2022 at 10:25 AM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > > > Add special hook for architecture to verify or setup addr, size
> > > > or prot when ioremap() or iounmap(), which will make the generic
> > > > ioremap more useful.
> > > >
> > > >     arch_ioremap() return a pointer,
> > > >       - IS_ERR means return an error
> > > >       - NULL means continue to remap
> > > >       - a non-NULL, non-IS_ERR pointer is directly returned
> > > >     arch_iounmap() return a int value,
> > > >       - 0 means continue to vunmap
> > > >       - error code means skip vunmap and return directly
> > > >
> > > > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > > I don't really like interfaces that mix error pointers and NULL pointer
> > > returns.
> > >
> > > Would it be possible to have a special error code other than NULL
> > > for the fallback case?
> > I don't find a good error code, maybe  ENOTSUPP, any better suggestion?
> I had another look at the resulting arm64 function, and it appears that
> you never actually return a non-error pointer here. If I didn't miss anything,
> I think the best way would be to change the return type to just indicate
> success or an error code, and drop the case of returning the actual result,
> and changing the function name accordingly.
>
> Would that work, or do you actually require returning an __iomem
> token from somewhere else?

Christoph  suggested in the first version,

https://lore.kernel.org/linux-arm-kernel/Ymq2uX%2FY15HlIpo7@xxxxxxxxxxxxx/

>         Arnd
>
> .