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

[Kefeng Wang]

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?
>         arnd
>
> .