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

[Arnd Bergmann]

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?

       arnd