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List:       linux-spi
Subject:    Re: [PATCH v2 3/4] ACPI / scan: Recognize Apple SPI and I2C slaves
From:       Mika Westerberg <mika.westerberg () linux ! intel ! com>
Date:       2017-06-29 9:22:22
Message-ID: 20170629092222.GC629 () lahna ! fi ! intel ! com
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On Thu, Jun 29, 2017 at 10:46:04AM +0200, Lukas Wunner wrote:
> On Thu, Jun 29, 2017 at 10:34:20AM +0300, Mika Westerberg wrote:
> > On Wed, Jun 28, 2017 at 07:20:19PM +0200, Lukas Wunner wrote:
> > > --- a/drivers/acpi/scan.c
> > > +++ b/drivers/acpi/scan.c
> > > @@ -1444,6 +1444,12 @@ static bool acpi_is_spi_i2c_slave(struct acpi_device *device)
> > >  	struct list_head resource_list;
> > >  	bool is_spi_i2c_slave = false;
> > >  
> > > +	/* Macs use device properties in lieu of _CRS resources */
> > > +	if (IS_ENABLED(CONFIG_X86) && dmi_match(DMI_SYS_VENDOR, "Apple Inc.") &&
> > 
> > Do we really need these checks?
> 
> With these checks present, searching for the properties can be optimized
> away on ARM and skipped on x86 non-Macs.  (Each property query requires
> decoding the _DSD Package and performing an O(n) search of the properties.)

Well, you add dmi_match() that gets called every time and I was under
the impression that we already performed _DSD decode when the property
set was initially parsed.

Those checks just uglify the code IMHO.

No strong feelings though, so up to Rafael to decide :-)
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