From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Hans de Goede <hdegoede@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Carlo Caione <carlo@endlessm.com>
Subject: Re: [PATCH] ACPI / LPSS: Add device link for CHT SD card dependency on I2C
Date: Mon, 04 Dec 2017 15:56:23 +0100
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On Monday, December 4, 2017 3:33:29 PM CET Hans de Goede wrote:
> Hi,
> 
> On 04-12-17 15:30, Adrian Hunter wrote:
> > On 04/12/17 15:48, Hans de Goede wrote:
> >> Hi,
> >>
> >> Wouldn't it be easier to use the ACPI _DEP tracking for this, e.g.
> > 
> > It is using _DEP, see acpi_lpss_dep()
> > 
> >> add something like this to the the probe function:
> >>
> >>      struct acpi_device = ACPI_COMPANION(device);
> >>
> >>      if (acpi_device->dep_unmet)
> >>          return -EPROBE_DEFER;
> >>
> >> No idea if this will work, but if it does work, using the deps described
> >> in the ACPI tables seems like a better solution then hardcoding this.
> > 
> > That would not work because there are other devices listed in the _DEP
> > method so dep_unmet is always true.  So we are left checking _DEP but only
> > for specific device dependencies.
> 
> Ugh, understood thank you for explaining this. Perhaps it is a good idea
> to mention in the commit message why acpi_dev->dep_unmet cannot be used
> here?

Not just in the commit message, but I'd suggest adding a comment to that effect
next to the definition of lpss_device_links[].

Thanks,
Rafael