linux-kernel - Re: [PATCH V3 0/3] PNP: Allow PNP resources to be disabled (interface)

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Date:	Thu, 02 Aug 2012 23:57:06 +0200
From:	Witold Szczeponik <Witold.Szczeponik@....net>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Borislav Petkov <bp@...en8.de>, bhelgaas@...gle.com,
	lenb@...nel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH V3 0/3] PNP: Allow PNP resources to be disabled (interface)

On 02/08/12 23:40, Rafael J. Wysocki wrote:

> On Thursday, August 02, 2012, Witold Szczeponik wrote:
>> On 02/08/12 22:09, Rafael J. Wysocki wrote:
>>> On Monday, July 30, 2012, Borislav Petkov wrote:
>>>> On Sun, Jul 29, 2012 at 09:31:53PM +0200, Witold Szczeponik wrote:

[... snip ...]

>>>>
>>>> Shouldn't this be rather "disable_irq" or something which is a single
>>>> word and thus would simplify parsing a lot?
>>>
>>> Or just "irq", which isn't going to be confused with anything else it seems.
>>>
>>> Thanks,
>>> Rafael
>>>
>>
>> Hi Rafael, 
>>
>> the code in "drivers/pnp/interface.c" implements a (non-trivial) interface
>> which accepts the keywords "disable", "activate", "fill", "auto", "clear",
>> and "get" as simple, one word commands.  The remaining "set" command is
>> more complex, for it determines which resource is to be set ("io", "mem",
>> "irq", "dma", and "bus"), followed by the actual value(s) of this resource
>> (e.g., "0x0200-0x021f", or "7"). 
>>
>> The patch series allows to use the term "disabled" or "<none>" as a 
>> resource value (c.f. my example above) when needed (c.f. my motivation for
>> the patch series). 
>>
>> We could, of course, change the parser in "interface.c", but this would 
>> change the ABI, I am afraid.  Something that I'd rather not do... 
> 
> Still, you _are_ doing that by extending the ABI, aren't you?

As the special value "disabled" is available as of these patches, one could
consider this an extension.  I agree. 

> 
>> I hope, this makes the scope of the patch series clear(er).
> 
> Yes, it does, thanks.
> 
> My opinion is that the whole interface is wrong and should be changed.  How to
> do that is a different matter that would require some consideration.  Perhaps
> the least painful way would be to add a new, hopefully better, interface along
> with the old one and then deprecate the latter at one point.

Personally, I too think that the PNP ABI in sysfs has its rough edges.  However, 
as with the deprecation of any existing ABI, this would require a new ABI first, 
then some time where the old and new ABI live in co-existence, and then to remove 
the currently available ABI. 

> 
> Now, since I don't like the existing interface, I'd prefer it not to be
> extended.

The current ABI does not allow for the kernel to run on my hardware: this is 
a/the problem.  The proposed extension fixes the problem.  

While I agree with your first statement, for the time being I do not see a 
better solution other than to extend the ABI. 

At this point I am repeating my "call for comments" to the community. :-) 

--- Witold

> 
> Thanks,
> Rafael
> 
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