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Subject: Re: [PATCH 4.4 28/74] ACPI / scan: Prefer devices without _HID/_CID
 for _ADR matching
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Hans de Goede <hdegoede@redhat.com>
References: <20180129123847.507563674@linuxfoundation.org>
 <20180129123848.888319573@linuxfoundation.org>
 <ffdd5d23-0080-6b00-1b46-2b7952200ac7@suse.cz>
From:   Jiri Slaby <jslaby@suse.cz>
Message-ID: <bdb6b0ed-0c79-0053-ddd3-78da186fc33e@suse.cz>
Date:   Thu, 1 Feb 2018 09:57:21 +0100
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On 02/01/2018, 09:46 AM, Jiri Slaby wrote:
> On 01/29/2018, 01:56 PM, Greg Kroah-Hartman wrote:
>> 4.4-stable review patch.  If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> commit c2a6bbaf0c5f90463a7011a295bbdb7e33c80b51 upstream.
>>
>> The way acpi_find_child_device() works currently is that, if there
>> are two (or more) devices with the same _ADR value in the same
>> namespace scope (which is not specifically allowed by the spec and
>> the OS behavior in that case is not defined), the first one of them
>> found to be present (with the help of _STA) will be returned.
>>
>> This covers the majority of cases, but is not sufficient if some of
>> the devices in question have a _HID (or _CID) returning some valid
>> ACPI/PNP device IDs (which is disallowed by the spec) and the
>> ASL writers' expectation appears to be that the OS will match
>> devices without a valid ACPI/PNP device ID against a given bus
>> address first.
>>
>> To cover this special case as well, modify find_child_checks()
>> to prefer devices without ACPI/PNP device IDs over devices that
>> have them.
>>
>> Suggested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Tested-by: Hans de Goede <hdegoede@redhat.com>
>> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> 
> You seem you took this from SLE12-SP2? But where did you take the
> upstream commit SHA from? In SLE, I have "Git-commit: fdad4e7a876a2..."
> which is the correct SHA of this patch. The above c2a6bbaf0c is a
> different patch. So are your scripts broken or is this a manual oversight?

Not only the SHA, the whole commit message is taken from c2a6bbaf0c. But
the diff below is fdad4e7a876a2.

To clarify: upstream c2a6bbaf0c is in 4.4.80 already (as f4a42f8492).
The diff below is a fix for it with upstream SHA fdad4e7a876a2 (in 4.4
as 1fe277d48f). So the code is correct, unlike meta data.

>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>
>> ---
>>  drivers/acpi/glue.c |   12 ++++++------
>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> --- a/drivers/acpi/glue.c
>> +++ b/drivers/acpi/glue.c
>> @@ -99,13 +99,13 @@ static int find_child_checks(struct acpi
>>  		return -ENODEV;
>>  
>>  	/*
>> -	 * If the device has a _HID (or _CID) returning a valid ACPI/PNP
>> -	 * device ID, it is better to make it look less attractive here, so that
>> -	 * the other device with the same _ADR value (that may not have a valid
>> -	 * device ID) can be matched going forward.  [This means a second spec
>> -	 * violation in a row, so whatever we do here is best effort anyway.]
>> +	 * If the device has a _HID returning a valid ACPI/PNP device ID, it is
>> +	 * better to make it look less attractive here, so that the other device
>> +	 * with the same _ADR value (that may not have a valid device ID) can be
>> +	 * matched going forward.  [This means a second spec violation in a row,
>> +	 * so whatever we do here is best effort anyway.]
>>  	 */
>> -	return sta_present && list_empty(&adev->pnp.ids) ?
>> +	return sta_present && !adev->pnp.type.platform_id ?
>>  			FIND_CHILD_MAX_SCORE : FIND_CHILD_MIN_SCORE;
>>  }

thanks,
-- 
js
suse labs