On Thu, Nov 1, 2018 at 2:21 AM João Paulo Rechi Vita <jprvita@xxxxxxxxx> wrote: > > Asus laptops have a hotkey function on the F7 key to turn the display > backlight OFF, labeled with a screen with a X inside, as shown on > https://dlcdnimgs.asus.com/websites/global/products/Xep1ZcSY8dyWXK11/images/keyboard.png > > This hotkey worked on very few Asus models, where the EC acts on the > backlight and input events are generated only to notify userspace of the > backlight status. On these machines the first hotkey press turns the > display backlight OFF and notifies the OS with 0x34, which asus-nb-wmi > forwards to userspace as KEY_DISPLAY_OFF, and a second press turns it > back ON and notifies the OS with 0x33, which asus-nb-wmi forwards to > userspace as KEY_DISPLAYTOGGLE. No other keys turn the display backlight > back ON, but their input is forwarded normally to the application under > focus. > > But for the majority of models, the EC actually does not act on the > backlight and we simply get a 0x33 notification every time the key is > pressed, or alternating values of 0x33 / 0x34. We have confirmed this > behavior on the following models: E203NAS, GL553VE, X441NC, X441UVK, > X541UVK, X555DG, X555UB, X555UQ, X560UD, X570ZD and X705FD, and the DSDT > on these machines and the working one (only confirmed on N552VW) is the > same for the query involved here. > > After trying to get information from Asus for quite some time on how > this works on Windows, we finally recently got a contact that was able > to give us a definitive answer and a specification for this feature. > According this contact the 0x33 / 0x34 is an old behavior and all newer > machines should only be notifying the OS with 0x35 instead, as newer ECs > don't control the backlight anymore. When a 0x35 notification is > received the OS should act on the display backlight. From the spec > (machine-translated from Chinese): > > 1.4 Fn+F7 > Function introduction > > After the user presses Fn + F7, the screen will be closed through the > Windows API. The user will immediately open the screen with the mouse > and keyboard. > The API used can be found in the Sample URL: > https://code.msdn.microsoft.com/windowsdesktop/Coalescable-Timer-Sample-d9da954c > BIOS implementation > Increase Notify code > LCD On: 0x33 (display OSD) > LCD Off: 0x34 (display OSD) > LCD Switch: 0x35 (using API switch) > > The behavior on Windows with the ATKACPI driver from Asus installed > matches what is described above, with the hotkey turning OFF the > backlight of all connected displays with a fading effect, and any cursor > input or key press turning the backlight back ON. The key press or > cursor input is passed through to the application under focus or under > the cursor. > > With this information from the spec, a simple analysis of the DSDT > (pasted on the first commit of this series) shows that in order to have > the firmware notify the OS with 0x35 and have the OS act on the > backlight, we need to call WMNB(ASUS_WMI_DEVID_BACKLIGHT==0x00050011, 2) > on the _WDG device. Then we can simply map that scan code to the > appropriate key code in the driver. > > In include/uapi/linux/input-event-codes.h KEY_DISPLAY_OFF is defined as > "display device to off state", but it is not actually handled by > userspace on a GNOME+Xorg stack. There are also KEY_SCREENSAVER and > KEY_SCREENLOCK / KEY_COFFEE. The former seems to be ignored by userspace > as well (and its value is higher than 255 so it can't be handled by Xorg > IIUC), and the later is mapped to XF86ScreenSaver by Xorg and triggers > the lock screen action on GNOME. KEY_SCREENLOCK seems to be what closest > matches the behavior described above in a Xorg world. I am not sure if > any of this changes with Wayland, so any clarifications in that regard > would be greatly appreciated. > Pushed to my review and testing queue, thanks! > João Paulo Rechi Vita (3): > asus-wmi: Tell the EC the OS will handle the display off hotkey > asus-nb-wmi: Map 0x35 to KEY_SCREENLOCK > asus-nb-wmi: Drop mapping of 0x33 and 0x34 scan codes > > drivers/platform/x86/asus-nb-wmi.c | 3 +-- > drivers/platform/x86/asus-wmi.c | 3 ++- > 2 files changed, 3 insertions(+), 3 deletions(-) > > -- > 2.19.1 > -- With Best Regards, Andy Shevchenko
