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[ Upstream commit bee447e224b2645911c5d06e35dc90d8433fcef6 ] The DDC/CI protocol involves sending a multi-byte request to the display via I2C, which is typically followed by a multi-byte response. The internal I2C controller only allows single byte reads/writes or reads of 8 sequential bytes, hence DDC/CI is not supported when the internal I2C controller is used. The I2C transfers complete without errors, however the data in the response is garbage. Abort transfers to/from slave address 0x37 (DDC) with -EOPNOTSUPP, to make it evident that the communication is failing. Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Reviewed-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Sean Paul <sean@poorly.run> Acked-by: Neil Armstrong <narmstrong@baylibre.com> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191002124354.v2.1.I709dfec496f5f0b44a7b61dcd4937924da8d8382@changeid Signed-off-by: Sasha Levin <sashal@kernel.org>
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.