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

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Date:	Mon, 30 Jul 2012 12:58:16 +0200
From:	"Witold Szczeponik" <Witold.Szczeponik@....net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...nel.org, bhelgaas@...gle.com, rjw@...k.pl
Subject: Re: [PATCH V3 0/3] PNP: Allow PNP resources to be disabled (interface)

> On Sun, Jul 29, 2012 at 09:31:53PM +0200, Witold Szczeponik wrote:
> > the aim is to select a PNP ACPI option where resources can be disabled
> > (or are not needed).  E.g., the parallel port of the 600E can be used
> > with and without IRQ lines.  The means to allow for this is to use the
> > sysfs interface to select disabled resources (just like any other 
> > resource value).  In https://lkml.org/lkml/2011/7/3/41, I used the 
> > following example:
> > 
> >   echo disable > /sys/bus/pnp/devices/$device/resources
> >   echo clear > /sys/bus/pnp/devices/$device/resources
> >   echo set irq disabled > /sys/bus/pnp/devices/$device/resources
> >   echo fill > /sys/bus/pnp/devices/$device/resources
> >   echo activate > /sys/bus/pnp/devices/$device/resources
> > 
> > The third line is made possible by the patch series.  All other
> > lines are already implemented.
> 
> Shouldn't this be rather "disable_irq" or something which is a single
> word and thus would simplify parsing a lot?
> 
> Also, <Documentation/filesystems/sysfs.txt> says
> 
> "Attributes should be ASCII text files, preferably with only one value
> per file. It is noted that it may not be efficient to contain only one
> value per file, so it is socially acceptable to express an array of
> values of the same type."
> 
> Thanks.
> 
> -- 
> Regards/Gruss,
>     Boris.

Hi Boris, 

the patch series is about adding the term "disabled" (or "<none") to
the list of possible values for resources.  The current state of the
kernel ABI already allows to use the following statement (cf. DSDT
excerpt from https://lkml.org/lkml/2011/7/3/41): 

  echo set irq 7 > /sys/bus/pnp/devices/$device/resources

i.e., the "resources" file can already parse all the values necessary for setting PNP values.  

The patch series is not about adding a new ABI or changing an existing ABI.  It is about extending the existing one to be able to handle the term "disabled" (or "<none>") as a special for a resource value. 

--- Witold
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