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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: Hans de Goede <hdegoede@redhat.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.