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The camera driver passes messages back and forth between the firmware with requests and replies. One of the fields of the message header called context is a pointer so the size changes between 32 bit and 64 bit. The context field is used to pair reply messages from the firmware with request messages from the kernel. The simple solution would be to use the padding field for the upper 32 bits of pointers, but this would rely on the firmware always copying the pad field. So instead handles are generated that are 32 bit numbers and a mapping stored in a btree as implemented by the btree library in the kernel lib directory. The mapping pairs the handle with the pointer to the actual data. The btree library was chosen since it's very easy to use and red black trees would be overkill. The camera driver also now forces in the btree library if the camera is included in the build. The btree library is a hidden configuration option. Signed-off-by: Michael Zoran <mzoran@crowfest.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.