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platform/x86: dell-rbtn: Improve explanation about DELLABC6 

According to Mario at Dell, the DELLABC6 device should not be used on a
Linux system. It also conflicts with Intel-HID and its interactions with
Network Manager. Document that we are aware of the device, but that we
are intentionally ignoring it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
[dvhart: New commit message and minor comment wording fixes]
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: "Pali Rohár" <pali.rohar@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
This commit is contained in:
Andy Lutomirski 2016-02-17 12:43:06 -08:00 committed by Darren Hart (VMware)
parent e4f2e3f0ea
commit 5d4be5f2b1
1 changed files with 20 additions and 9 deletions
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29
drivers/platform/x86/dell-rbtn.c
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@ -221,16 +221,27 @@ static const struct acpi_device_id rbtn_ids[] = {
/*
* This driver can also handle the "DELLABC6" device that
* appears on the XPS 13 9350, but that device is disabled
* by the DSDT unless booted with acpi_osi="!Windows 2012"
* acpi_osi="!Windows 2013". Even if we boot that and bind
* the driver, we seem to have inconsistent behavior in
* which NetworkManager can get out of sync with the rfkill
* state.
* appears on the XPS 13 9350, but that device is disabled by
* the DSDT unless booted with acpi_osi="!Windows 2012"
* acpi_osi="!Windows 2013".
*
* On the XPS 13 9350 and similar laptops, we're not supposed to
* use DELLABC6 at all. Instead, we handle the rfkill button
* via the intel-hid driver.
* According to Mario at Dell:
*
* DELLABC6 is a custom interface that was created solely to
* have airplane mode support for Windows 7. For Windows 10
* the proper interface is to use that which is handled by
* intel-hid. A OEM airplane mode driver is not used.
*
* Since the kernel doesn't identify as Windows 7 it would be
* incorrect to do attempt to use that interface.
*
* Even if we override _OSI and bind to DELLABC6, we end up with
* inconsistent behavior in which userspace can get out of sync
* with the rfkill state as it conflicts with events from
* intel-hid.
*
* The upshot is that it is better to just ignore DELLABC6
* devices.
*/
{ "", 0 },