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It is possible to update the backlight power and the brightness using the sysfs and on writing it either returns the count or if the callback function does not exist then returns the error code 'ENXIO'. We have a situation where the userspace client is writing to the sysfs to update the power and since the callback function exists the client receives the return value as count and considers the operation to be successful. That is correct as the write to the sysfs was successful. But there is no way to know if the actual operation was done or not. backlight_update_status() returns the error code if it fails. Pass that to the userspace client who is trying to update the power so that the client knows that the operation failed. Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.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.