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 10:05:26 +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'

Hi!

Am 26.06.2013 09:56, schrieb Chen Gang:
> On 06/26/2013 02:54 PM, Richard Weinberger wrote:
>> Hi!
>>
>> Am 26.06.2013 08:31, schrieb Chen Gang:
>>> For "User Mode Linux", it may enable 'MMU', but not need implement
>>> ioremap and iounmap, so "include/asm-generic/io.h" need notice this
>>> case to keep itself 'generic'.
>>>
>>> The related error (with allmodconfig, without pcap):
>>>
>>>     CC [M]  drivers/ptp/ptp_pch.o
>>>   drivers/ptp/ptp_pch.c: In function �pch_remove�:
>>>   drivers/ptp/ptp_pch.c:571:3: error: implicit declaration of function �iounmap� [-Werror=implicit-function-declaration]
>>>   drivers/ptp/ptp_pch.c: In function �pch_probe�:
>>>   drivers/ptp/ptp_pch.c:621:2: error: implicit declaration of function �ioremap� [-Werror=implicit-function-declaration]
>>>   drivers/ptp/ptp_pch.c:621:13: warning: assignment makes pointer from integer without a cast [enabled by default]
>>>   cc1: some warnings being treated as errors
>>>
>>>
>>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
>>> ---
>>>  arch/um/include/asm/Kbuild |    1 +
>>>  include/asm-generic/io.h   |    6 +++---
>>>  2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
>>> index b30f34a..a34ea5d 100644
>>> --- a/arch/um/include/asm/Kbuild
>>> +++ b/arch/um/include/asm/Kbuild
>>> @@ -3,3 +3,4 @@ generic-y += hw_irq.h irq_regs.h kdebug.h percpu.h sections.h topology.h xor.h
>>>  generic-y += ftrace.h pci.h io.h param.h delay.h mutex.h current.h exec.h
>>>  generic-y += switch_to.h clkdev.h
>>>  generic-y += trace_clock.h
>>> +generic-y += io.h
>>
>> We include that file already. See three lines above.
>>
> 
> Oh, really it is, thanks.
> 
>>> 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.


> 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

Thanks,
//richard
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