• Daniel Drake's avatar
    Input: synaptics - add support for Relative mode · 7968a5dd
    Daniel Drake authored
    Currently, the synaptics driver puts the device into Absolute mode.
    As explained in the synaptics documentation section 3.2, in this mode,
    the device sends a continuous stream of packets at the maximum rate
    to the host when the user's fingers are near or on the pad or
    pressing buttons, and continues streaming for 1 second afterwards.
    These packets are even sent when there is no new information to report,
    even when they are duplicates of the previous packet.
    
    For embedded systems this is a bit much - it results in a huge
    and uninterrupted stream of interrupts at high rate.
    
    This patch adds support for Relative mode, which can be selected as
    a new psmouse protocol. In this mode, the device does not send duplicate
    packets and acts like a standard PS/2 mouse. However, synaptics-specific
    functionality is still available, such as the ability to set the packet
    rate, and rather than disabling gestures and taps at the hardware level
    unconditionally, a 'synaptics_disable_gesture' sysfs attribute has
    been added to allow control of this functionality.
    
    This solves a long standing OLPC issue: synaptics hardware enables
    tap to click by default (even in the default relative mode), but we
    have found this to be inappropriate for young children and first
    time computer users. Enabling the synaptics driver disables tap-to-click,
    but we have previously been unable to use this because it also enables
    Absolute mode, which is too "spammy" for our desires and actually
    overloads our EC with its continuous stream of packets. Now we can enable
    the synaptics driver, disabling tap to click while retaining the less
    noisy Relative mode.
    Signed-off-by: default avatarDaniel Drake <dsd@laptop.org>
    Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
    7968a5dd
synaptics.h 6.41 KB