The system normally has kernel headers shipped with the distribution.
These typically lag behind actual kernel releases. Thus they would not
have the latest API additions, such as the V4L2 request API this driver
uses.
However, it is also bad practice to just install new kernel headers into
the system wide default location, as there may be some differences
between it and what the C library was built against.
Add an option to specify a path to a set of up-to-date kernel headers.
This would allow the user to build this project in a safe but working
environment.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Chen-Yu Tsai