From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: Re: [PATCH 2/3] acpi i2c: Initialize info.type from of_compatible
Date: Fri, 17 Jun 2016 15:19:28 +0300
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To: Crestez Dan Leonard <leonard.crestez@intel.com>
Cc: linux-acpi@vger.kernel.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <lenb@kernel.org>, linux-i2c@vger.kernel.org, Wolfram Sang <wsa@the-dreams.de>, linux-spi@vger.kernel.org, Mark Brown <broonie@kernel.org>, linux-kernel@vger.kernel.org, Octavian Purdila <octavian.purdila@intel.com>, Jarkko Nikula <jarkko.nikula@intel.com>

On Fri, Jun 17, 2016 at 03:07:39PM +0300, Crestez Dan Leonard wrote:
> On 06/16/2016 11:11 AM, Mika Westerberg wrote:
> > On Wed, Jun 15, 2016 at 09:30:28PM +0300, Crestez Dan Leonard wrote:
> >> When using devicetree i2c_board_info.type is set to the compatible
> >> string with the vendor prefix removed. For I2C devices described via
> >> ACPI the i2c_board_info.type string is set to the ACPI device name. When
> >> using ACPI and DT ids this string ends up something like "PRP0001:00".
> >>
> >> If the of_compatible property is present try to use that instead. This
> >> makes it easier to instantiate i2c drivers through ACPI with DT ids.
> > 
> > Adding Jarkko -- he was the original author of I2C/SPI device naming in
> > ACPI. Since this only affects devices with PRP0001 in their _HID/_CID,
> > it should not break anything.
> 
> It's possible to have something like this:
> 
>             Name (_HID, "XXX1234")
>             Name (_CID, "PRP0001")
>             Name (_DSD, Package () {
>                 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>                 Package () {
>                     Package () {"compatible", "vendor,x1234"},
>                 }
>             })
> 
> With these patches the i2c device name changes from "XXX1234:00" to
> "x1234". This would happen even if a driver matches the XXX1234 acpi ID.
> It's not clear if anyone actually uses that or if this change would be
> harmful.

I have not seen a single machine using _DSD with PRP0001 so I don't
think it is a problem.

> It theory it would be possible to use of_compatible for naming only if
> there are no other real IDs. I don't think it's worthwhile.

I agree.