linux-kernel - Re: [PATCH v3 4/6] mm: ioremap: Add arch

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Message-ID: <CAK8P3a1DbNY6NzcwzjVFvd9yw6L3YBHQos_hmE=nG=6cuv1DAg@mail.gmail.com>
Date:   Tue, 24 May 2022 14:37:40 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Christoph Hellwig <hch@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v3 4/6] mm: ioremap: Add arch_ioremap/iounmap()

On Thu, May 19, 2022 at 10:25 AM Kefeng Wang <wangkefeng.wang@...wei.com> 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@...wei.com>

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