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

From: Arnd Bergmann <arnd@arndb.de>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: kernel test robot <lkp@intel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	kbuild-all@lists.01.org, Linux-MM <linux-mm@kvack.org>,
	Christoph Hellwig <hch@infradead.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH v3 4/6] mm: ioremap: Add arch_ioremap/iounmap()
Date: Tue, 24 May 2022 14:35:27 +0200	[thread overview]
Message-ID: <CAK8P3a1qEk3hLUOijtzXRhT4-nZO8KUe1a_3mvUVSSzaGt2itg@mail.gmail.com> (raw)
In-Reply-To: <c4ea8f50-f445-f4ee-1d17-f21954e52a83@huawei.com>

On Tue, May 24, 2022 at 11:48 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >>> mm/ioremap.c:59:16: sparse: sparse: incorrect type in argument 1 (different address spaces) @@     expected void const *addr @@     got void [noderef] __iomem *vaddr @@
> >     mm/ioremap.c:59:16: sparse:     expected void const *addr
> >     mm/ioremap.c:59:16: sparse:     got void [noderef] __iomem *vaddr
> >
> > vim +59 mm/ioremap.c
> >
> >      51
> >      52       void iounmap(volatile void __iomem *addr)
> >      53       {
> >      54               void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
> >      55
> >      56               if (arch_iounmap(vaddr))
> >      57                       return;
> >      58
> >    > 59               vunmap(vaddr);
>
> 1) Will add generic "arch_ioremap/arch_iounmap define"
>
> 2) and change this to vunmap((void *)vaddr);

I think this need an extra __force to actually suppress the sparse
warning, as in

        vunmap((void __force *)vaddr);

Using __force is usually wrong, this is one of the exceptions, so
maybe add a comment
as well.

         Arnd