dell-rbtn: Add a comment about the XPS 13 9350

On the XPS 13 9350, the dell-rbtn mechanism has a new device id, and
the DSDT turns it off if a new enough _OSI is supported.  Add a
comment about why we don't bother supporting it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

diff --git a/drivers/platform/x86/dell-rbtn.c b/drivers/platform/x86/dell-rbtn.c
index cd410e3..b51a200 100644 (file)
--- a/drivers/platform/x86/dell-rbtn.c
+++ b/drivers/platform/x86/dell-rbtn.c
@@ -217,6 +217,21 @@ static void rbtn_notify(struct acpi_device *device, u32 event);
 static const struct acpi_device_id rbtn_ids[] = {
        { "DELRBTN", 0 },
        { "DELLABCE", 0 },
+
+       /*
+        * 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.
+        *
+        * 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.
+        */
+
        { "", 0 },
 };