• Hans de Goede's avatar
    i2c: acpi: Do not create i2c-clients for LNXVIDEO ACPI devices · 3a4991a9
    Hans de Goede authored
    ACPI video devices get tagged by the kernel with the custom LNXVIDEO
    HID so that normal pnp-id matching can be used and are handled by the
    acpi-video driver.
    
    Sometimes the ACPI nodes describing these contain a SERIAL_TYPE_I2C ACPI
    resource. Before this commit the presence of this resource would cause the
    i2c-core to create a /sys/bus/i2c/devices/i2c-LNXVIDEO:00 device for this
    with a modalias of: "i2c:LNXVIDEO:00".
    
    There is no i2c driver for this custom HID, the acpi-video driver binds
    directly to the ACPI device /sys/bus/acpi/devices/LNXVIDEO\:00 which has
    a modalias of "acpi:LNXVIDEO:" .
    
    Not only is the creation of an i2c-client for this undesirable, it is
    actually causing problems. This weird pseudo-resource claims an i2c
    speed of 100KHz and typically points to the i2c bus which is used by the
    touchscreen controller. Some touchscreen controllers only work properly at
    400KHz, at 100KHz they cause errors like these:
    
    i2c_designware 80860F41:03: i2c_dw_handle_tx_abort: lost arbitration
    i2c_designware 80860F41:03: i2c_dw_handle_tx_abort: lost arbitration
    i2c_designware 80860F41:03: i2c_dw_handle_tx_abort: lost arbitration
    i2c_designware 80860F41:03: i2c_dw_handle_tx_abort: lost arbitration
    silead_ts i2c-MSSL1680:00: Registers clear error -11
    
    This commit makes the i2c-core ignore LNXVIDEO compatible ACPI devices
    which has 2 positive results:
    
    1) The bogus i2c-client for these is no longer created.
    2) i2c_acpi_lookup_speed now ignores the 100KHz speed from the pseudo
    i2c-resouce and properly returns 400KHz as speed for the touchscreen
    i2c bus, fixing the touchscreen not working on various devies.
    Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
    Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
    Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
    3a4991a9
i2c-core-acpi.c 15.6 KB