i915: Fix opregion notifications

opregion-based platforms will send ACPI video event 0x80 for a range of
notification types for legacy compatibility. This is interpreted as a
display switch event, which may not be appropriate in the circumstances.
When we receive such an event we should make sure that the platform is
genuinely requesting a display switch before passing that event through
to userspace.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Tested-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index d2c710422908..b7c5ddb564d1 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -297,19 +297,26 @@ static int intel_opregion_video_event(struct notifier_block *nb,
         /* The only video events relevant to opregion are 0x80. These indicate
            either a docking event, lid switch or display switch request. In
            Linux, these are handled by the dock, button and video drivers.
-           We might want to fix the video driver to be opregion-aware in
-           future, but right now we just indicate to the firmware that the
-           request has been handled */
+        */
 
         struct opregion_acpi *acpi;
+        struct acpi_bus_event *event = data;
+        int ret = NOTIFY_OK;
+
+        if (strcmp(event->device_class, ACPI_VIDEO_CLASS) != 0)
+                return NOTIFY_DONE;
 
         if (!system_opregion)
                 return NOTIFY_DONE;
 
         acpi = system_opregion->acpi;
+
+        if (event->type == 0x80 && !(acpi->cevt & 0x1))
+                ret = NOTIFY_BAD;
+
         acpi->csts = 0;
 
-        return NOTIFY_OK;
+        return ret;
 }
 
 static struct notifier_block intel_opregion_notifier = {