Re: [PATCH] iio: dac: ad5593r: Dynamically set AD5593R channel modes

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: "Hennerich, Michael" <Michael.Hennerich@analog.com>
Cc: AceLan Kao <acelan.kao@canonical.com>,
	"Ardelean, Alexandru" <alexandru.Ardelean@analog.com>,
	William Sung <william.sung@advantech.com.tw>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Jonathan Cameron <jic23@kernel.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	linux-iio <linux-iio@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Campion Kang <Campion.Kang@advantech.com.tw>
Subject: Re: [PATCH] iio: dac: ad5593r: Dynamically set AD5593R channel modes
Date: Wed, 2 Sep 2020 11:52:29 +0300	[thread overview]
Message-ID: <CAHp75VdvnUsEf=fsRQRmyxQO=1m09M5U19GBtSPkjxSGA5cRBA@mail.gmail.com> (raw)
In-Reply-To: <BN6PR03MB25968259EBEAD55E040367308E2F0@BN6PR03MB2596.namprd03.prod.outlook.com>

On Wed, Sep 2, 2020 at 11:09 AM Hennerich, Michael
<Michael.Hennerich@analog.com> wrote:
> > From: Andy Shevchenko <andy.shevchenko@gmail.com>
> > Sent: Montag, 31. August 2020 14:46
> > On Mon, Aug 31, 2020 at 2:28 PM AceLan Kao <acelan.kao@canonical.com>
> > wrote:

...

> > P.S. Jonathan, it seems this driver has artificial ACPI HID. We probably have to
> > remove it. However, ADS is indeed reserved for Analog Devices in PNP registry.
> > Can we have AD's official answer on this?
> > Cc'ing additional AD people.
>
> Agreed, this ID was chosen under the PNP ID Vendor Space for Analog Devices Inc.
> Days back, I did a quick kernel grep, and there are many drivers which use the 3-letter
> PNP ID as acpi_device_id. So, I thought this being not an issue.

No, no, the use of PNP ID is not an issue. The point is if the ID is
artificial or official.

> I'm against removing it since I know people shipping this in their ACPI tables already.

I see. Can we consider this email as the official answer from AD that
this ID is being allocated for this certain component?

> Regarding ACPI DSD customization, one way to do this is to move this into the BIOS.
> This way the particular piece of HW can be customized rather than manage HW
> connections in software.

Assuming the confirmation on the above, indeed, one may use ACPI HID
with DSD properties in the firmware. Main purpose of PRP0001 is the
*development* stage of the product at which a vendor should take care
about allocation of proper ACPI IDs for the components in use. Yes, I
know that this is not always feasible b/c some HW component vendors
don't care about ACPI at all.

-- 
With Best Regards,
Andy Shevchenko