On Tue, Oct 08, 2013 at 08:59:58AM +0300, Terje Bergström wrote:
On 07.10.2013 11:34, Thierry Reding wrote:
Most of the included files are either not required or already included by some other header file.
What's the general policy? I personally feel that each source file should #include all the header files it needs, and should not rely on header files #including other header files.
This way if header file A stops needing header file B, we don't need to go and fix all users of header file A that assume B is included.
I've been hit by this multiple times in Linux kernel - sometimes some header files just assume another header file is #included and refuses to compile it it isn't.
Explicit includes are probably the safest route when dealing with headers from include/linux, which can be volatile. However, in this case any of the general header files are already included by driver private header files, which are not subject to the same volatility. Or when they change we'll see breakage immediately because pretty much everything about the driver will be rebuilt.
It even has the advantage that if a file in include/linux or include/drm changes in a way that breaks compilation, we only have to change one of the driver private headers instead of all source files.
Thierry