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128 lines
4.6 KiB
ReStructuredText
128 lines
4.6 KiB
ReStructuredText
.. _t440_support:
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==============================================================================
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Lenovo \*40 series touchpad support
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==============================================================================
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The Lenovo \*40 series emulates trackstick buttons on the top part of the
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touchpads.
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.. _t440_support_overview:
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------------------------------------------------------------------------------
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Overview
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------------------------------------------------------------------------------
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The Lenovo \*40 series introduced a new type of touchpad. Previously, all
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laptops had a separate set of physical buttons for the
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`trackstick <http://en.wikipedia.org/wiki/Pointing_stick>`_. This
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series removed these buttons, relying on a software emulation of the top
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section of the touchpad. This is visually marked on the trackpad itself,
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and clicks can be triggered by pressing the touchpad down with a finger in
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the respective area:
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.. figure:: top-software-buttons.svg
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:align: center
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Left, right and middle-button click with top software button areas
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This page only covers the top software buttons, the bottom button behavior
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is covered in :ref:`Clickpad software buttons <clickpad_softbuttons>`.
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Clickpads with a top button area are marked with the
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`INPUT_PROP_TOPBUTTONPAD <https://www.kernel.org/doc/Documentation/input/event-codes.txt>`_
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property.
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.. _t440_support_btn_size:
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------------------------------------------------------------------------------
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Size of the buttons
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------------------------------------------------------------------------------
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The size of the buttons matches the visual markings on this touchpad.
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The width of the left and right buttons is approximately 42% of the
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touchpad's width, the middle button is centered and assigned 16% of the
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touchpad width.
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The line of the buttons is 5mm from the top edge of the touchpad,
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measurements of button presses showed that the size of the buttons needs to
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be approximately 10mm high to work reliable (especially when using the
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thumb to press the button).
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.. _t440_support_btn_behavior:
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------------------------------------------------------------------------------
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Button behavior
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------------------------------------------------------------------------------
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Movement in the top button area does not generate pointer movement. These
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buttons are not replacement buttons for the bottom button area but have
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their own behavior. Semantically attached to the trackstick device, libinput
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re-routes events from these buttons to appear through the trackstick device.
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.. graphviz::
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digraph top_button_routing
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{
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rankdir="LR";
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node [shape="box";]
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trackstick [label="trackstick kernel device"];
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touchpad [label="touchpad kernel device"];
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subgraph cluster0 {
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bgcolor = floralwhite
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label = "libinput"
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libinput_ts [label="trackstick libinput_device"
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style=filled
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fillcolor=white];
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libinput_tp [label="touchpad libinput_device"
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style=filled
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fillcolor=white];
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libinput_tp -> libinput_ts [constraint=false
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color="red4"];
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}
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trackstick -> libinput_ts [arrowhead="none"]
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touchpad -> libinput_tp [color="red4"]
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events_tp [label="other touchpad events"];
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events_topbutton [label="top software button events"];
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libinput_tp -> events_tp [arrowhead="none"]
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libinput_ts -> events_topbutton [color="red4"]
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}
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The top button areas work even if the touchpad is disabled but will be
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disabled when the trackstick device is disabled. If the finger starts inside
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the top area and moves outside the button area the finger is treated as dead
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and must be lifted to generate future buttons. Likewise, movement into the
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top button area does not trigger button events, a click has to start inside
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this area to take effect.
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.. _t440_support_identification:
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------------------------------------------------------------------------------
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Kernel support
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------------------------------------------------------------------------------
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The firmware on the first generation of touchpads providing top software
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buttons is buggy and announces wrong ranges.
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`Kernel patches <https://lkml.org/lkml/2014/3/7/722>`_ are required;
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these fixes are available in kernels 3.14.1, 3.15 and later but each
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touchpad needs a separate fix.
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The October 2014 refresh of these laptops do not have this firmware bug
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anymore and should work without per-device patches, though
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`this kernel commit <http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=02e07492cdfae9c86e3bd21c0beec88dbcc1e9e8>`_
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is required.
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For a complete list of supported touchpads check
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`the kernel source <http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/input/mouse/synaptics.c>`_
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(search for "topbuttonpad_pnp_ids").
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