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    SubjectRe: [PATCH 4/9 v4] Input: synaptics - add image sensor support
    On 08/18/2011 04:28 AM, Daniel Kurtz wrote:
    > Synaptics makes (at least) two kinds of touchpad sensors:
    > * Older pads use a profile sensor that could only infer the location
    > of individual fingers based on the projection of their profiles
    > onto row and column sensors.
    > * Newer pads use an image sensor that can track true finger position
    > using a two-dimensional sensor grid.
    >
    > Both sensor types support an "Advanced Gesture Mode":
    > When multiple fingers are detected, the touchpad sends alternating
    > "Advanced Gesture Mode" (AGM) and "Simple Gesture Mode" (SGM)
    > packets.
    > The AGM packets have w=2, and contain reduced resolution finger data
    > The SGM packets have w={0,1} and contain full resolution finger data
    >
    > Profile sensors try to report the "upper" (larger y value) finger in
    > the SGM packet, and the lower (smaller y value) in the AGM packet.
    > However, due to the nature of the profile sensor, they easily get
    > confused when fingers cross, and can start reporting the x-coordinate
    > of one with the y-coordinate of the other. Thus, for profile
    > sensors, "semi-mt" was created, which reports a "bounding box"
    > created by pairing min and max coordinates of the two pairs of
    > reported fingers.
    >
    > Image sensors can report the actual coordinates of two of the fingers
    > present. This patch detects if the touchpad is an image sensor and
    > reports finger data using the MT-B protocol.
    >
    > NOTE: This patch only adds partial support for 2-finger gestures.
    > The proper interpretation of the slot contents when more than
    > two fingers are present is left to later patches. Also,
    > handling of 'number of fingers' transitions is incomplete.
    >
    > Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>

    Acked-by: Chase Douglas <chase.douglas@canonical.com>


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