linux-kernel - Re: [PATCH 2/4] mm: ioremap: Add arch_ioremap/iounmap

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Message-ID: <a0e058a5-3f46-1d05-5007-d339fa50e957@huawei.com>
Date:   Thu, 28 Apr 2022 14:20:25 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Arnd Bergmann <arnd@...db.de>
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>
Subject: Re: [PATCH 2/4] mm: ioremap: Add arch_ioremap/iounmap_check()


On 2022/4/28 2:20, Arnd Bergmann wrote:
> On Wed, Apr 27, 2022 at 2:14 PM Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
>> @@ -964,6 +964,9 @@ static inline void iounmap(volatile void __iomem *addr)
>>   #elif defined(CONFIG_GENERIC_IOREMAP)
>>   #include <linux/pgtable.h>
>>
>> +bool arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot);
>> +bool arch_iounmap_check(void __iomem *addr);
>> +
>>   void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot);
>>   void iounmap(volatile void __iomem *addr);
>>
>> diff --git a/mm/ioremap.c b/mm/ioremap.c
>> index 522ef899c35f..d1117005dcc7 100644
>> --- a/mm/ioremap.c
>> +++ b/mm/ioremap.c
>> @@ -11,6 +11,16 @@
>>   #include <linux/io.h>
>>   #include <linux/export.h>
>>
>> +bool __weak arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot)
>> +{
>> +       return true;
>> +}
>> +
>> +bool __weak arch_iounmap_check(void __iomem *addr)
>> +{
>> +       return true;
>> +}
>> +
> I don't really like the weak functions. The normal way to do this in
> asm-generic headers
> is to have something like
>
> #ifndef arch_ioremap_check
> static inline bool arch_ioremap_check(phys_addr_t addr, size_t size,
> unsigned long prot)
> {
>         return true;
> }
> #endif
>
> and then in architectures that actually do some checking, have these
> bits in asm/io.h
>
> bool arch_ioremap_check(phys_addr_t addr, size_t size, unsigned long prot);
> #define arch_ioremap_check arch_ioremap_check
Ok, I could use this way, and keep consistent with others definitions in 
asm/io.h
> (or alternatively an extern declaration, if the implementation is nontrivial)
>
> It may be worth pointing out that either way requires including
> asm-generic/io.h,
> which most architectures don't. This is probably fine, as only csky, riscv and
> now arm64 use CONFIG_GENERIC_IOREMAP, and we can probably require
> that any further architectures using this symbol also have to use
> asm-generic/io.h.

It looks the arch is already include it,

$ git grep "asm-generic/io.h" arch/

arch/arc/include/asm/io.h:#include <asm-generic/io.h>
arch/arm/include/asm/io.h:#include <asm-generic/io.h>
arch/arm64/include/asm/io.h:#include <asm-generic/io.h>
arch/csky/include/asm/io.h:#include <asm-generic/io.h>
arch/h8300/include/asm/io.h:#include <asm-generic/io.h>
arch/ia64/include/asm/io.h:#include <asm-generic/io.h>
arch/m68k/include/asm/io.h:#include <asm-generic/io.h>
arch/m68k/include/asm/io_no.h: * that behavior here first before we 
include asm-generic/io.h.
arch/microblaze/include/asm/io.h:#include <asm-generic/io.h>
arch/nios2/include/asm/io.h:#include <asm-generic/io.h>
arch/openrisc/include/asm/io.h:#include <asm-generic/io.h>
arch/powerpc/include/asm/io.h:#include <asm-generic/io.h>
arch/riscv/include/asm/io.h:#include <asm-generic/io.h>
arch/s390/include/asm/io.h:#include <asm-generic/io.h>
arch/sparc/include/asm/io_32.h:#include <asm-generic/io.h>
arch/um/include/asm/io.h:#include <asm-generic/io.h>
arch/x86/include/asm/io.h:#include <asm-generic/io.h>
arch/xtensa/include/asm/io.h:#include <asm-generic/io.h>

>        Arnd
>
> .