linux-kernel - Re: [PATCH] include/asm-generic/io.h: add 'UML' case just like 'no-MMU'

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Date:	Wed, 26 Jun 2013 16:34:20 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Richard Weinberger <richard@....at>
CC:	Jeff Dike <jdike@...toit.com>, Arnd Bergmann <arnd@...db.de>,
	dhsharp@...gle.com,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>,
	uml-user <user-mode-linux-user@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] include/asm-generic/io.h: add 'UML' case just like 'no-MMU'

On 06/26/2013 04:05 PM, Richard Weinberger wrote:
>>>> >>> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
>>>> >>> index d5afe96..e80331d 100644
>>>> >>> --- a/include/asm-generic/io.h
>>>> >>> +++ b/include/asm-generic/io.h
>>>> >>> @@ -303,10 +303,10 @@ static inline void *phys_to_virt(unsigned long address)
>>>> >>>  /*
>>>> >>>   * Change "struct page" to physical address.
>>>> >>>   *
>>>> >>> - * This implementation is for the no-MMU case only... if you have an MMU
>>>> >>> + * This implementation is for the no-MMU or UML case only... if you have an MMU
>>>> >>>   * you'll need to provide your own definitions.
>>>> >>>   */
>>>> >>> -#ifndef CONFIG_MMU
>>>> >>> +#if !CONFIG_MMU || CONFIG_UML
>>>> >>>  static inline void __iomem *ioremap(phys_addr_t offset, unsigned long size)
>>>> >>>  {
>>>> >>>  	return (void __iomem*) (unsigned long)offset;
>>>> >>> @@ -325,7 +325,7 @@ static inline void __iomem *ioremap(phys_addr_t offset, unsigned long size)
>>>> >>>  static inline void iounmap(void __iomem *addr)
>>>> >>>  {
>>>> >>>  }
>>>> >>> -#endif /* CONFIG_MMU */
>>>> >>> +#endif /* !CONFIG_MMU || CONFIG_UML */
>>>> >>>  
>>>> >>>  #ifdef CONFIG_HAS_IOPORT
>>>> >>>  #ifndef CONFIG_GENERIC_IOMAP
>>>> >>>
>>> >>
>>> >> UML has no io memory but a MMU, so I'd argue that you better fix drivers/ptp/ptp_pch.c dependencies.
>>> >> _If_ ptp_pch.c really works without real io memory, you can look what I did in my GENERIC_IO series[1]
>>> >> to make nandsim work on UML. Maybe this helps.
>>> >>
>> > 
>> > But "no io memory" is not the excuse to not define the related dummy
>> > function.
> UML has no io memory, period.
> Same applies for s390, it also includes asm-generic/io.h in the !CONFIG_PCI
> case.
> UML and s390 are very special here.
> 

Oh, yes, really the same.

>> > The drivers internal code has already check the related return value,
>> > so it is the architecture's duty to 'tell' the driver whether support
>> > io memory (e.g. define ioremap, but return NULL).
> It does so already by setting CONFIG_HAS_IOMEM=n

Excuse me, I use "grep -rn ioremap *" under "include/" and "arch/um/"
directory, but can not find the related definition for 'ioremap'.

Is there another declaration or definition way which I don't know ?
(maybe it is).

For our case, the ".config" file does not define 'CONFIG_HAS_IOMEM', can
I assume it means "CONFIG_HAS_IOMEM=n" ?


Thanks
-- 
Chen Gang

Asianux Corporation
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