[Intel-gfx] How to disable (not working) native backlight support?

[Niccolò Belli]

I have a Samsung X360 laptop and I always used the samsung-backlight 
patches. (Un?)fortunately since 2.6.39 they merged native backlight 
support, it would have been a wonderful news if it would have worked 
flawlessly. Unfortunately sometimes it does not work, the screen 
flickers and /var/log/messages if full of tons of

Aug 18 18:39:47 laptop logger: ACPI event unhandled: 
video/brightnessdown BRTDN 00000087 00000000

If I apply samsung-backlight on top of >=2.6.39 I get:


Aug 18 18:35:00 laptop kernel: [  117.717567] samsung_backlight: found 
laptop model 'X360'
Aug 18 18:35:00 laptop kernel: [  117.717591] ------------[ cut here 
]------------
Aug 18 18:35:00 laptop kernel: [  117.717599] WARNING: at 
drivers/video/backlight/backlight.c:314 
backlight_device_register+0xfb/0x16e()
Aug 18 18:35:00 laptop kernel: [  117.717603] Hardware name: X360 

Aug 18 18:35:00 laptop kernel: [  117.717606] samsung: invalid backlight 
type
Aug 18 18:35:00 laptop kernel: [  117.717608] Modules linked in: 
samsung_backlight(+) snd_hda_codec_realtek iwlagn(+) mac80211 sg 
snd_hda_intel(+) snd_hda_codec snd_hwdep tpm_tis tpm samsung_laptop 
snd_pcm tpm_bios snd_timer psmouse iTCO_wdt cfg80211 snd 
iTCO_vendor_support serio_raw soundcore pcspkr rfkill snd_page_alloc 
sky2 battery thermal fan evdev container ac processor power_supply
Aug 18 18:35:00 laptop kernel: [  117.717645] Pid: 401, comm: modprobe 
Not tainted 3.0.0-gentoo #1
Aug 18 18:35:00 laptop kernel: [  117.717648] Call Trace:
Aug 18 18:35:00 laptop kernel: [  117.717655]  [<ffffffff81042d65>] ? 
warn_slowpath_common+0x78/0x8c
Aug 18 18:35:00 laptop kernel: [  117.717661]  [<ffffffff81042e18>] ? 
warn_slowpath_fmt+0x45/0x4a
Aug 18 18:35:00 laptop kernel: [  117.717667]  [<ffffffff812b7f7d>] ? 
device_private_init+0x3a/0x40
Aug 18 18:35:00 laptop kernel: [  117.717673]  [<ffffffff8122dd01>] ? 
backlight_device_register+0xfb/0x16e
Aug 18 18:35:00 laptop kernel: [  117.717679]  [<ffffffffa00d901a>] ? 
dmi_check_cb+0x1a/0x1a [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717686]  [<ffffffffa00d90e8>] ? 
samsung_init+0xce/0xfe6 [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717692]  [<ffffffffa00d901a>] ? 
dmi_check_cb+0x1a/0x1a [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717697]  [<ffffffff81002078>] ? 
do_one_initcall+0x78/0x131
Aug 18 18:35:00 laptop kernel: [  117.717703]  [<ffffffff8106f180>] ? 
sys_init_module+0xb7/0x207
Aug 18 18:35:00 laptop kernel: [  117.717710]  [<ffffffff81403d52>] ? 
system_call_fastpath+0x16/0x1b
Aug 18 18:35:00 laptop kernel: [  117.717713] ---[ end trace 
c6966c0be6e01b72 ]---
Aug 18 18:35:00 laptop kernel: [  117.717725] ------------[ cut here 
]------------
Aug 18 18:35:00 laptop kernel: [  117.717732] WARNING: at 
fs/sysfs/dir.c:455 sysfs_add_one+0x8c/0x9e()
Aug 18 18:35:00 laptop kernel: [  117.717735] Hardware name: X360 

Aug 18 18:35:00 laptop kernel: [  117.717737] sysfs: cannot create 
duplicate filename '/class/backlight/samsung'
Aug 18 18:35:00 laptop kernel: [  117.717740] Modules linked in: 
samsung_backlight(+) snd_hda_codec_realtek iwlagn(+) mac80211 sg 
snd_hda_intel(+) snd_hda_codec snd_hwdep tpm_tis tpm samsung_laptop 
snd_pcm tpm_bios snd_timer psmouse iTCO_wdt cfg80211 snd 
iTCO_vendor_support serio_raw soundcore pcspkr rfkill snd_page_alloc 
sky2 battery thermal fan evdev container ac processor power_supply
Aug 18 18:35:00 laptop kernel: [  117.717772] Pid: 401, comm: modprobe 
Tainted: G        W   3.0.0-gentoo #1
Aug 18 18:35:00 laptop kernel: [  117.717774] Call Trace:
Aug 18 18:35:00 laptop kernel: [  117.717779]  [<ffffffff81042d65>] ? 
warn_slowpath_common+0x78/0x8c
Aug 18 18:35:00 laptop kernel: [  117.717784]  [<ffffffff81042e18>] ? 
warn_slowpath_fmt+0x45/0x4a
Aug 18 18:35:00 laptop kernel: [  117.717789]  [<ffffffff811399ec>] ? 
sysfs_add_one+0x8c/0x9e
Aug 18 18:35:00 laptop kernel: [  117.717793]  [<ffffffff8113a6f5>] ? 
sysfs_do_create_link+0x100/0x1a7
Aug 18 18:35:00 laptop kernel: [  117.717799]  [<ffffffff812b85c1>] ? 
device_add+0x216/0x5d0
Aug 18 18:35:00 laptop kernel: [  117.717805]  [<ffffffff810372c4>] ? 
complete_all+0x32/0x41
Aug 18 18:35:00 laptop kernel: [  117.717810]  [<ffffffff8122dd12>] ? 
backlight_device_register+0x10c/0x16e
Aug 18 18:35:00 laptop kernel: [  117.717816]  [<ffffffffa00d901a>] ? 
dmi_check_cb+0x1a/0x1a [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717822]  [<ffffffffa00d90e8>] ? 
samsung_init+0xce/0xfe6 [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717829]  [<ffffffffa00d901a>] ? 
dmi_check_cb+0x1a/0x1a [samsung_backlight]
Aug 18 18:35:00 laptop kernel: [  117.717833]  [<ffffffff81002078>] ? 
do_one_initcall+0x78/0x131
Aug 18 18:35:00 laptop kernel: [  117.717838]  [<ffffffff8106f180>] ? 
sys_init_module+0xb7/0x207
Aug 18 18:35:00 laptop kernel: [  117.717843]  [<ffffffff81403d52>] ? 
system_call_fastpath+0x16/0x1b
Aug 18 18:35:00 laptop kernel: [  117.717846] ---[ end trace 
c6966c0be6e01b73 ]---



How can I disable native backlight support so that I can apply 
samsung-backlight flawlessly?

Thank you,
Darkbasic