Samsung Galaxy Book DriverÂķ

Joshua Grisham <josh@joshuagrisham.com>

This is a Linux x86 platform driver for Samsung Galaxy Book series notebook devices which utilizes Samsung’s SCAI ACPI device in order to control extra features and receive various notifications.

Supported devicesÂķ

Any device with one of the supported ACPI device IDs should be supported. This covers most of the “Samsung Galaxy Book” series notebooks that are currently available as of this writing, and could include other Samsung notebook devices as well.

StatusÂķ

The following features are currently supported:

Because different models of these devices can vary in their features, there is logic built within the driver which attempts to test each implemented feature for a valid response before enabling its support (registering additional devices or extensions, adding sysfs attributes, etc). Therefore, it can be important to note that not all features may be supported for your particular device.

The following features might be possible to implement but will require additional investigation and are therefore not supported at this time:

  • “Dolby Atmos” mode for the speakers

  • “Outdoor Mode” for increasing screen brightness on models with SAM0427

  • “Silent Mode” on models with SAM0427

Keyboard backlightÂķ

A new LED class named samsung-galaxybook::kbd_backlight is created which will then expose the device using the standard sysfs-based LED interface at /sys/class/leds/samsung-galaxybook::kbd_backlight. Brightness can be controlled by writing the desired value to the brightness sysfs attribute or with any other desired userspace utility.

Note

Most of these devices have an ambient light sensor which also turns off the keyboard backlight under well-lit conditions. This behavior does not seem possible to control at this time, but can be good to be aware of.

Performance modeÂķ

This driver implements the Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile) interface for working with the “performance mode” function of the Samsung ACPI device.

Mapping of each Samsung “performance mode” to its respective platform profile is performed dynamically by the driver, as not all models support all of the same performance modes. Your device might have one or more of the following mappings:

  • “Silent” maps to low-power

  • “Quiet” maps to quiet

  • “Optimized” maps to balanced

  • “High performance” maps to performance

The result of the mapping can be printed in the kernel log when the module is loaded. Supported profiles can also be retrieved from /sys/firmware/acpi/platform_profile_choices, while /sys/firmware/acpi/platform_profile can be used to read or write the currently selected profile.

The balanced platform profile will be set during module load if no profile has been previously set.

Battery charge control end thresholdÂķ

This platform driver will add the ability to set the battery’s charge control end threshold, but does not have the ability to set a start threshold.

This feature is typically called “Battery Saver” by the various Samsung applications in Windows, but in Linux we have implemented the standardized “charge control threshold” sysfs interface on the battery device to allow for controlling this functionality from the userspace.

The sysfs attribute /sys/class/power_supply/BAT1/charge_control_end_threshold can be used to read or set the desired charge end threshold.

If you wish to maintain interoperability with the Samsung Settings application in Windows, then you should set the value to 100 to represent “off”, or enable the feature using only one of the following values: 50, 60, 70, 80, or 90. Otherwise, the driver will accept any value between 1 and 100 as the percentage that you wish the battery to stop charging at.

Note

Some devices have been observed as automatically “turning off” the charge control end threshold if an input value of less than 30 is given.

Firmware AttributesÂķ

The following enumeration-typed firmware attributes are set up by this driver and should be accessible under /sys/class/firmware-attributes/samsung-galaxybook/attributes/ if your device supports them:

  • power_on_lid_open (device should power on when the lid is opened)

  • usb_charging (USB ports can deliver power to connected devices even when the device is powered off or in a low sleep state)

  • block_recording (blocks access to camera and microphone)

All of these attributes are simple boolean-like enumeration values which use 0 to represent “off” and 1 to represent “on”. Use the current_value attribute to get or change the setting on the device.

Note that when block_recording is updated, the input device “Samsung Galaxy Book Lens Cover” will receive a SW_CAMERA_LENS_COVER switch event which reflects the current state.

Keyboard hotkey actions (i8042 filter)Âķ

The i8042 filter will swallow the keyboard events for the Fn+F9 hotkey (Multi- level keyboard backlight toggle) and Fn+F10 hotkey (Block recording toggle) and instead execute their actions within the driver itself.

Fn+F9 will cycle through the brightness levels of the keyboard backlight. A notification will be sent using led_classdev_notify_brightness_hw_changed so that the userspace can be aware of the change. This mimics the behavior of other existing devices where the brightness level is cycled internally by the embedded controller and then reported via a notification.

Fn+F10 will toggle the value of the “block recording” setting, which blocks or allows usage of the built-in camera and microphone (and generates the same Lens Cover switch event mentioned above).

ACPI notifications and hotkey actionsÂķ

ACPI notifications will generate ACPI netlink events under the device class samsung-galaxybook and bus ID matching the Samsung ACPI device ID found on your device. The events can be received using userspace tools such as acpi_listen and acpid.

The Fn+F11 Performance mode hotkey will be handled by the driver; each keypress will cycle to the next available platform profile.