linux-kernel - Re: [PATCH v3 01/11] ACPI: delay enumeration of devices with a

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Message-ID: <0c08069e-7758-fc09-c200-d867d097b499@redhat.com>
Date:   Mon, 11 Oct 2021 09:11:05 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Mark Gross <markgross@...nel.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Daniel Scally <djrscally@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Len Brown <lenb@...nel.org>,
        linux-acpi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Kate Hsuan <hpa@...hat.com>, linux-media@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v3 01/11] ACPI: delay enumeration of devices with a _DEP
 pointing to an INT3472 device

Hi,

On 10/11/21 8:19 AM, Mika Westerberg wrote:
> Hi,
> 
> On Sun, Oct 10, 2021 at 08:56:57PM +0200, Hans de Goede wrote:
>> +/* List of HIDs for which we honor deps of matching ACPI devs, when checking _DEP lists. */
>> +static const char * const acpi_honor_dep_ids[] = {
>> +	"INT3472", /* Camera sensor PMIC / clk and regulator info */
> 
> Is there some reason why we can't do this for all devices with _DEP?
> That way we don't need to maintain lists like this.

Up until now the ACPI core deliberate mostly ignores _DEP-s because the
_DEP method may point to pretty much any random ACPI object and Linux does
not necessarily have a driver for all ACPI objects the driver points too,
which would lead to the devices never getting instantiated.

In hindsight this might not have been the best solution (1), but if we
now start honoring _DEP-s for all devices all of a sudden then this
will almost certainly lead to a whole bunch of regressions.

Note that in this case the HID which triggers this is for the device
being depended upon and for all camera sensors used with the IPU3 and
IPU4 Intel camera blocks this is the INT3472 device. By triggering on
this HID (rather then on the sensor HIDs) I expect that we will not
need to update this list all that often.

Regards,

Hans

1) I believe that Windows does pay more reference to the _DEP-s and we've
had some other related issues lately.