linux-kernel - Re: [PATCH 2/4] ACPI: Make acpi_dev_get

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Date:   Wed, 26 Jul 2017 02:23:10 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Robert Moore <robert.moore@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>, Feng Kan <fkan@....com>,
        Jon Masters <jcm@...hat.com>, Zhang Rui <rui.zhang@...el.com>,
        Nate Watterson <nwatters@...eaurora.org>
Subject: Re: [PATCH 2/4] ACPI: Make acpi_dev_get_resources() method agnostic

On Tuesday, July 25, 2017 10:15:38 AM Lorenzo Pieralisi wrote:
> On Sat, Jul 22, 2017 at 12:05:39AM +0200, Rafael J. Wysocki wrote:
> > On Thursday, July 20, 2017 03:45:14 PM Lorenzo Pieralisi wrote:
> > > The function acpi_dev_get_resources() is completely generic and
> > > can be used to parse resource objects that are not necessarily
> > > coming from the _CRS method but also from other objects eg _DMA
> > > that have the same _CRS resource format.
> > > 
> > > Create an acpi_dev_get_resources() helper, internal to the ACPI
> > > resources parsing compilation unit, acpi_dev_get_resources_method(),
> > > that takes a char* parameter to detect which ACPI method should be
> > > called to retrieve the resources list and make acpi_dev_get_resources()
> > > call it with a method name _CRS leaving the API behaviour unchanged.
> > > 
> > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> > > Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> > > ---
> > >  drivers/acpi/resource.c | 54 +++++++++++++++++++++++++++++--------------------
> > >  1 file changed, 32 insertions(+), 22 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
> > > index cd4c427..2b20a09 100644
> > > --- a/drivers/acpi/resource.c
> > > +++ b/drivers/acpi/resource.c
> > > @@ -573,6 +573,36 @@ static acpi_status acpi_dev_process_resource(struct acpi_resource *ares,
> > >  	return AE_OK;
> > >  }
> > >  
> > > +static
> > > +int acpi_dev_get_resources_method(struct acpi_device *adev,
> > 
> > Do not break lines like this, please.
> > 
> > It should be
> > 
> > static int acpi_dev_get...
> > 
> > Also I would call it differently, maybe simply __acpi_dev_get_resources()?
> > 
> > > +				  struct list_head *list,
> > > +				  int (*preproc)(struct acpi_resource *, void *),
> > > +				  void *preproc_data, char *method)
> > 
> > const char *method ?
> 
> drivers/acpi/resource.c: In function '__acpi_dev_get_resources':
> drivers/acpi/resource.c:587:37: warning: passing argument 2 of
> 'acpi_has_method' discards 'const' qualifier from pointer target type
> [-Wdiscarded-qualifiers]
>   if (!acpi_has_method(adev->handle, method))
>                                        ^~~~~~
> In file included from ./include/linux/acpi.h:44:0,
>                  from drivers/acpi/resource.c:21:
> 		 ./include/acpi/acpi_bus.h:55:6: note: expected 'char *'
> 		 but argument is of type 'const char *'
> 		  bool acpi_has_method(acpi_handle handle, char *name);
> 
> Same problem with acpi_walk_resources().
> 
> So either I fiddle (eg cast the const away) with the method string 
> in __acpi_dev_get_resources() or I can add an int/bool to detect
> which method to use ( _CRS or _DMA) instead of passing a const char *.

No, that'd be overkill.  Let's keep the (char *) in there.

Thanks,
Rafael