From: Rafael J. Wysocki Date: Fri, 30 Dec 2016 01:27:31 +0000 (+0100) Subject: ACPI / scan: Prefer devices without _HID/_CID for _ADR matching X-Git-Tag: v4.10-rc3~15^2~1 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c2a6bbaf0c5f;p=karo-tx-linux.git ACPI / scan: Prefer devices without _HID/_CID for _ADR matching 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 Signed-off-by: Rafael J. Wysocki Tested-by: Hans de Goede --- diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c index eb709e7c9ffd..fb19e1cdb641 100644 --- a/drivers/acpi/glue.c +++ b/drivers/acpi/glue.c @@ -98,7 +98,15 @@ static int find_child_checks(struct acpi_device *adev, bool check_children) if (check_children && list_empty(&adev->children)) return -ENODEV; - return sta_present ? FIND_CHILD_MAX_SCORE : FIND_CHILD_MIN_SCORE; + /* + * 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.] + */ + return sta_present && list_empty(&adev->pnp.ids) ? + FIND_CHILD_MAX_SCORE : FIND_CHILD_MIN_SCORE; } struct acpi_device *acpi_find_child_device(struct acpi_device *parent,