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

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Message-ID: <51CAA8D6.9000505@nod.at>
Date:	Wed, 26 Jun 2013 10:39:50 +0200
From:	Richard Weinberger <richard@....at>
To:	Chen Gang <gang.chen@...anux.com>
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'

Am 26.06.2013 10:34, schrieb Chen Gang:
> 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).

Both UML and s390 (in the !CONFIG_PCI) do not define ioremap() because
without io memory you cannot have a ioremap().

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

If I'm not mistaken it works the other way around.
All archs except UML and s390 set CONFIG_HAS_IOMEM=y.

Thanks,
//richard
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