linux-kernel - Re: [PATCH v2 1/5] memblock test: fix implicit declaration of function 'virt_to

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Message-ID: <20240802005353.z6udm2tw45i7phqy@master>
Date: Fri, 2 Aug 2024 00:53:53 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: Wei Yang <richard.weiyang@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH v2 1/5] memblock test: fix implicit declaration of
 function 'virt_to_phys'

On Thu, Aug 01, 2024 at 09:09:14AM +0300, Mike Rapoport wrote:
>On Thu, Aug 01, 2024 at 12:07:39AM +0000, Wei Yang wrote:
>> On Mon, Jul 29, 2024 at 08:37:23AM +0300, Mike Rapoport wrote:
>> >On Mon, Jul 29, 2024 at 01:47:21AM +0000, Wei Yang wrote:
>> >> Commit 94ff46de4a73 ("memblock: Move late alloc warning down to phys
>> >> alloc") introduce the usage of virt_to_phys(), which is not defined in
>> >> memblock tests.
>> >> 
>> >> Define it in mm.h to fix the build error.
>> >> 
>> >> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
>> >> 
>> >> ---
>> >> v2: move definition to mm.h
>> >> ---
>> >>  tools/include/linux/mm.h | 2 ++
>> >>  1 file changed, 2 insertions(+)
>> >> 
>> >> diff --git a/tools/include/linux/mm.h b/tools/include/linux/mm.h
>> >> index cad4f2927983..9db45c5d00fc 100644
>> >> --- a/tools/include/linux/mm.h
>> >> +++ b/tools/include/linux/mm.h
>> >> @@ -20,6 +20,8 @@
>> >>  #define pfn_to_page(pfn) ((void *)((pfn) * PAGE_SIZE))
>> >>  
>> >>  #define phys_to_virt phys_to_virt
>> >> +#define virt_to_phys(p) ((unsigned long)p)
>> >> +
>> >
>> >Please don't break #define of phys_to_virt from the static inline
>> >implementation.
>> >
>> 
>> I don't touch the definition of phys_to_virt, so you are willing me to adjust
>> it?
>> 
>> The macro here will be expanded to code at preprocessing stage. I don't get
>> how static inline would help here. Do I miss something?
>
>static inline allows type checking of the parameters and #define with the
>same name as of the static inline allows catching other defines with the
>same name.
>
>So it's common practice to use this combination, line phys_to_virt does.
> 

Thanks, I finally get why we write code like this.

>> >And please make virt_to_phys a static inline similarly to phys_to_virt.
>> >
>> >>  static inline void *phys_to_virt(unsigned long address)
>> >>  {
>> >>  	return __va(address);
>> >> -- 
>> >> 2.34.1
>> >> 
>> >
>> >-- 
>> >Sincerely yours,
>> >Mike.
>> 
>> -- 
>> Wei Yang
>> Help you, Help me
>
>-- 
>Sincerely yours,
>Mike.

-- 
Wei Yang
Help you, Help me