Closed dos1 closed 6 years ago
hadess
commented
6 years ago Detecting tablet mode, or tent mode, is out of scope (and would be utterly unreliable if we did it based on the values of the accelerometers), and should be handled in the kernel and libinput, so that the keyboard and touchpad can be disabled appropriately.
About reporting the accelerometer reading values, see #166
dos1
commented
6 years ago I don't think that's right. While the 100%-keyboard-behind-the-screen tablet mode is indeed kernel/libinput thing, as it's usually based on hall sensor similarly to the lid switch (and there is some code for handling it already there), in some devices there's also a full range of motion available with so-called tent and presentation modes that has to be detected using values from multiple accelerometers (/gyros/inclinometers/etc.) and is definitely out of kernel and libinput scope.
I probably made a mistake by mentioning the tablet mode as an example, just thought it's the simplest one :P
But yeah, #166 seems like the interesting one.
hadess
commented
6 years ago I don't think that's right. While the 100%-keyboard-behind-the-screen tablet mode is indeed kernel/libinput thing, as it's usually based on hall sensor similarly to the lid switch (and there is some code for handling it already there), in some devices there's also a full range of motion available with so-called tent and presentation modes that has to be detected using values from multiple accelerometers (/gyros/inclinometers/etc.) and is definitely out of kernel and libinput scope.
The kernel wouldn't have to interpret the accelerometer readings, the BIOS or firmware usually does, and exports it. That's how modes toggling are usually implemented in platform drivers in the kernel. Then libinput sees a switch.
Look for Tablet swivel in https://www.kernel.org/doc/Documentation/laptops/thinkpad-acpi.txt
dos1
commented
6 years ago Yes, the BIOS even turns off the keyboard and its backlight automatically for me without Linux noticing at all. However, that doesn't use accelerometers at all, at least on my device, and is only a binary switch that detects whether the tablet mode is fully engaged or not (and it can be toggled with a magnet put into right place).
For other modes, you have to use two accelerometers, since otherwise when the screen stays in the same position and only the keyboard moves (but doesn't close completely on either of the screen sides), it's undetectable, and yet you might want to disable the keyboard and touchpad when the laptop is standing on them.
hadess
commented
6 years ago
Some laptops, especially laptop-convertibles with 360° hinges like Lenovo Yoga series, usually contain a pair of two sensors: an accelerometer mounted at the screen, and a gyroscope or a second accelerometer mounted at the keyboard.
iio-sensor-proxy could be extended to also provide the second orientation value, so use-cases like tent or tablet mode can be detected and supported.
It also has to be made sure that iio-sensor-proxy uses correct accelerometer for screen orientation purpose (not sure if it does already - my laptop has a gyro instead of 2nd accel). A case where there's only gyro(s) and no accels could also be considered - not sure if there's some hardware like that though.
[edit] I have played more and seems like the keyboard sensor isn't visible yet from Linux on my Yoga 2 Pro at all and the available gyroscope seems to come from the screen as well; however, some laptops do expose two accels already, see: https://github.com/alesguzik/linux_detect_tablet_mode so it could be supported by iio-sensor-proxy anyway.