Commit 9661e92c10a9775243c1ecb73373528ed8725a10: sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/device'

[Jeff Chua <jeff.chua.linux@gmail.com>]

Commit 9661e92c10a9775243c1ecb73373528ed8725a10 causes this bug. Reverting it solves the problem.

Notebook is Lenovo X201s.

Thanks,
Jeff



------------[ cut here ]------------
WARNING: at fs/sysfs/dir.c:455 sysfs_add_one+0x8c/0x9e()
Hardware name: 5413FGA
sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/device'
Modules linked in: i915(+) drm_kms_helper
Pid: 2010, comm: modprobe Not tainted 2.6.38 #15
Call Trace:
[<ffffffff81032548>] ? warn_slowpath_common+0x78/0x8c
[<ffffffff810325fb>] ? warn_slowpath_fmt+0x45/0x4a
[<ffffffff810f70bc>] ? sysfs_add_one+0x8c/0x9e
[<ffffffff810f7e21>] ? sysfs_do_create_link+0x100/0x1a7
[<ffffffff8123c054>] ? acpi_video_device_lcd_get_level_current+0x47/0x10e
[<ffffffff8123d076>] ? acpi_video_bus_add+0x961/0xc5b
[<ffffffff810f7798>] ? sysfs_addrm_finish+0x29/0xc2
[<ffffffff81219b7d>] ? acpi_device_probe+0x42/0x10d
[<ffffffff8128a83a>] ? driver_probe_device+0xa8/0x138
[<ffffffff8128a919>] ? __driver_attach+0x4f/0x6f
[<ffffffff8128a8ca>] ? __driver_attach+0x0/0x6f
[<ffffffff8128a0a4>] ? bus_for_each_dev+0x44/0x78
[<ffffffff81289a52>] ? bus_add_driver+0xb9/0x201
[<ffffffff8128ae45>] ? driver_register+0x90/0xf8
[<ffffffff8123c698>] ? acpi_video_register+0x1b/0x34
[<ffffffffa00104e0>] ? i915_driver_load+0xcb9/0xd99 [i915]
[<ffffffff8127a112>] ? drm_get_minor+0x209/0x25b
[<ffffffff8127bb79>] ? drm_get_pci_dev+0x14f/0x259
[<ffffffff811f6ce8>] ? local_pci_probe+0x49/0x93
[<ffffffff811f79ef>] ? pci_device_probe+0xbf/0xec
[<ffffffff8128a6f9>] ? driver_sysfs_add+0x66/0x8d
[<ffffffff8128a83a>] ? driver_probe_device+0xa8/0x138
[<ffffffff8128a919>] ? __driver_attach+0x4f/0x6f
[<ffffffff8128a8ca>] ? __driver_attach+0x0/0x6f
[<ffffffff8128a0a4>] ? bus_for_each_dev+0x44/0x78
[<ffffffff81289a52>] ? bus_add_driver+0xb9/0x201
[<ffffffff8128ae45>] ? driver_register+0x90/0xf8
[<ffffffff811f7c41>] ? __pci_register_driver+0x4e/0xc0
[<ffffffffa0051000>] ? i915_init+0x0/0x8d [i915]
[<ffffffffa0051000>] ? i915_init+0x0/0x8d [i915]
[<ffffffff81000208>] ? do_one_initcall+0x78/0x131
[<ffffffff8105bc32>] ? sys_init_module+0x97/0x1d5
[<ffffffff814b8592>] ? system_call_fastpath+0x16/0x1b
---[ end trace 7ad4522ea6dca630 ]---



commit 9661e92c10a9775243c1ecb73373528ed8725a10
Author: Matthew Garrett <mjg@redhat.com>
Date:   Tue Mar 22 16:30:25 2011 -0700

     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>

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index a9eec8c..a18e497 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);