On Mon, Jan 03, 2005 at 10:46:49 -0800, Om wrote: > Michael R. Hines wrote: > > > >The ones with underscores usually have matching functions withOUT > >underscores. They are meant to be private calls. > > > >The ones without underscores usually call the one with underscores, and > >these are the ones that actually do the work. > > > >The kernel will sometimes call the underscore'd functions directly > >because it knows what it's doing....... > > > >But while programming, we should generally call the ones without them. > Yes, unless we know what we do ;-) > for example, lets take arch/i386/lib/usercopy.c : copy_to_user(). This > function performs some checks (access_ok()) on the passed parameter and > then call the actual function that implements the functionlity > include/asm/uaccess.h:__copy_to_user(). The implementation might use > other functions as well. > > If the target area is already checked for access_ok, then the caller > call skip the call copy_to_user() and make a call directly to > __copy_to_user(). This will save some time/code size. > > I am not familiar with functions with single underscore starting. But > the idea is same. In fact I believe it's not. While __ means something like "bare bones version to use if you are sure you have made all sanity-checks and hold all the locks", _ rather means "this function isn't here". Symbols starting with one _ are traditionaly used for library symbols, that should have been static, but for some techical reason can't. I believe it's the same in kernel. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@xxxxxx>
Attachment:
signature.asc
Description: Digital signature
