acpi: tie ACPI backlight devices to PCI devices if possible

Dual-GPU machines may provide more than one ACPI backlight interface.  Tie
the backlight device to the GPU in order to allow userspace to identify
the correct interface.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index a9eec8c95a1f..a18e497f1c3c 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -782,6 +782,9 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
 
         if (acpi_video_backlight_support()) {
                 struct backlight_properties props;
+                struct pci_dev *pdev;
+                acpi_handle acpi_parent;
+                struct device *parent = NULL;
                 int result;
                 static int count = 0;
                 char *name;
@@ -794,10 +797,20 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
                         return;
                 count++;
 
+                acpi_get_parent(device->dev->handle, &acpi_parent);
+
+                pdev = acpi_get_pci_dev(acpi_parent);
+                if (pdev) {
+                        parent = &pdev->dev;
+                        pci_dev_put(pdev);
+                }
+
                 memset(&props, 0, sizeof(struct backlight_properties));
                 props.type = BACKLIGHT_FIRMWARE;
                 props.max_brightness = device->brightness->count - 3;
-                device->backlight = backlight_device_register(name, NULL, device,
+                device->backlight = backlight_device_register(name,
+                                                              parent,
+                                                              device,
                                                               &acpi_backlight_ops,
                                                               &props);
                 kfree(name);