after reading the overview of the uapi refactoring, let me summarize what i *think* is going on, point out some oddities, and ask some questions. (good writeup is here: http://lwn.net/Articles/507794/) first, a question -- is the uapi reorg meant to completely obsolete "make headers_install"? with userspace API content now broken off into its own uapi/ subdirectories, does this not make that target entirely superfluous? or is there something else happening here? i can see the Kbuild infrastructure is still there but, theoretically, why would it be necessary anymore given the refactoring? next, as i read it, all of the kernel header file content can be broken into exactly three (reasonable) categories: * kernel-only * shared between kernel and userspace * userspace only so far, so good, so let's look at each category. header files that contain kernel-only content should now reside in a "normal" include directory like include/linux and, as i read it, they shouldn't need any "__KERNEL__" preprocessor checks anymore, but there's still a lot of that: $ cd include/linux $ grep -r "#if.*__KERNEL__" * | wc -l 101 $ admittedly, those checks don't *hurt*, but is the plan that all of that eventually gets cleared out? in the other category/categories, we have all userspace content that should now be moved under some uapi/ directory. now those files *might* have checks of the form: #ifndef __KERNEL__ to reflect userspace-only content, that's fine. what they *shouldn't* have is: #ifdef __KERNEL__ since that reflects kernel space content and shouldn't be in a uapi/ directory, correct? unless, as i see it, it's a test that affects an actual structure definition, then there's really no way around it, like this in acct.h: #ifdef __KERNEL__ __u32 ac_etime; /* Elapsed Time */ #else float ac_etime; /* Elapsed Time */ #endif and i mentioned the strangeness with coda.h yesterday as well; here's the regular file: #if defined(__linux__) typedef unsigned long long u_quad_t; #else <-- that's a bit strange #endif #include <uapi/linux/coda.h> and here's the uapi version: ... snip ... #ifdef KERNEL <--- why is this here? typedef unsigned long u_long; typedef unsigned int u_int; typedef unsigned short u_short; typedef u_long ino_t; typedef u_long dev_t; typedef void * caddr_t; ... snip ... anyway, i'm sure this all works fine, but it certainly seems that there's a lot of leftover cruft that could still be deleted. is that still part of the plan? rday p.s. amusingly, what's still left in some of the uapi/ headers are *comments* referring to kernel checks that obviously don't exist anymore. eg., in include/uapi/linux/virtio_config.h: /* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so * anyone can use the definitions to implement compatible drivers/servers. i might throw together some cheap patches to get rid of that stuff. it offends my pedantic sensibilities. :-) -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================