On Wed, Aug 26, 2020 at 12:55:28PM +0300, Dan Carpenter wrote: > On Wed, Aug 26, 2020 at 07:21:35AM +0530, Allen Pais wrote: > > On Thu, Aug 20, 2020 at 3:09 AM James Bottomley > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Wed, 2020-08-19 at 21:54 +0530, Allen wrote: > > > > > [...] > > > > > > > Since both threads seem to have petered out, let me suggest in > > > > > > > kernel.h: > > > > > > > > > > > > > > #define cast_out(ptr, container, member) \ > > > > > > > container_of(ptr, typeof(*container), member) > > > > > > > > > > > > > > It does what you want, the argument order is the same as > > > > > > > container_of with the only difference being you name the > > > > > > > containing structure instead of having to specify its type. > > > > > > > > > > > > Not to incessantly bike shed on the naming, but I don't like > > > > > > cast_out, it's not very descriptive. And it has connotations of > > > > > > getting rid of something, which isn't really true. > > > > > > > > > > Um, I thought it was exactly descriptive: you're casting to the > > > > > outer container. I thought about following the C++ dynamic casting > > > > > style, so out_cast(), but that seemed a bit pejorative. What about > > > > > outer_cast()? > > > > > > > > > > > FWIW, I like the from_ part of the original naming, as it has > > > > > > some clues as to what is being done here. Why not just > > > > > > from_container()? That should immediately tell people what it > > > > > > does without having to look up the implementation, even before > > > > > > this becomes a part of the accepted coding norm. > > > > > > > > > > I'm not opposed to container_from() but it seems a little less > > > > > descriptive than outer_cast() but I don't really care. I always > > > > > have to look up container_of() when I'm using it so this would just > > > > > be another macro of that type ... > > > > > > > > > > > > > So far we have a few which have been suggested as replacement > > > > for from_tasklet() > > > > > > > > - out_cast() or outer_cast() > > > > - from_member(). > > > > - container_from() or from_container() > > > > > > > > from_container() sounds fine, would trimming it a bit work? like > > > > from_cont(). > > > > > > I'm fine with container_from(). It's the same form as container_of() > > > and I think we need urgent agreement to not stall everything else so > > > the most innocuous name is likely to get the widest acceptance. > > > > Kees, > > > > Will you be sending the newly proposed API to Linus? I have V2 > > which uses container_from() > > ready to be sent out. > > I liked that James swapped the first two arguments so that it matches > container_of(). Plus it's nice that when you have: > > struct whatever *foo = container_from(ptr, foo, member); > > Then it means that "ptr == &foo->member". I'm a bit stalled right now -- the merge window was keeping me busy, and this week is the Linux Plumbers Conference. This is on my list, but I haven't gotten back around to it. If you want, feel free to send the container_from() patch; you might be able to unblock this faster than me right now. :) -Kees -- Kees Cook
