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    SubjectRe: [RFC/RFT] [patch] Elo serial touchscreen driver
    Vojtech Pavlik wrote:
    > Hi!
    > I've written a driver for probably the most common touchscreen type -
    > the serial Elo touchscreen.

    If we are serious about getting support for serial touchscreens into the
    kernel, I can certainly give a hand there.

    I work for a company that develops software for restaurants, and we have
    a Linux port of our main application running in actual restaurants with
    a custom made Linux distribution for about 2 years now.

    We had to support a number of touchscreens, and we do it in the
    application itself, reading the serial port and processing the data.

    If this could go into the kernel, then our application needed only to
    read the input device, and handle events, no matter what touch screen
    was there. That would be a great improvement :)

    > The driver should handle all generations of serial Elos, as it handles
    > Elo 10-byte, 6-byte, 4-byte and 3-byte protocols.

    > I do not have any touchscreen, so I can't test the driver myself.

    I have one that uses the 10 byte protocol (I've never seen one ELOtouch
    that used one of the other protocols). I can give you some feedback as
    soon as I have some time to test it.

    > So if you have the time, please comment on the code of the patch,
    > and if you have an Elo, please try the driver with it.
    > [...]
    > + case 9:
    > + if (elo->csum) {
    > + input_regs(dev, regs);
    > + input_report_abs(dev, ABS_X, (elo->data[4] << 8) | elo->data[3]);
    > + input_report_abs(dev, ABS_Y, (elo->data[6] << 8) | elo->data[5]);
    > + input_report_abs(dev, ABS_PRESSURE, (elo->data[8] << 8) | elo->data[7]);
    > + input_report_key(dev, BTN_TOUCH, elo->data[8] || elo->data[7]);

    This one is weird. In my code I have this:

    > button = ((buf[2] & 0x03) != 0);

    So maybe, ELO touchscreens that don't have pressure sense output, only
    send "touch down / up" information on the 2 LSB's of the third byte(?)

    Anyway, inputattach should have a command line option to set the
    baudrate manually, as some of these touchscreens have configurable
    baudrates, and some POS manufacturers set them to non-default values.

    Also, I've already seen touchscreens where the POS manufacturer got the
    pin-out wrong (or something like that) so the touch reports the X
    coordinate where the Y should be, and vice-versa. I really don't know
    where this should be handled (driver, input layer, application?), but it
    must be handled somewhere for the applications to work.

    Paulo Marques -

    All that is necessary for the triumph of evil is that good men do nothing.
    Edmund Burke (1729 - 1797)
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