On Wed, Apr 3, 2024 at 5:13 AM Jonathan Corbet <corbet@xxxxxxx> wrote: > > So I'm not sure what your desired path for getting this upstream is. I > can take it, but I'm generally quite leery of taking coding-style > changes without some serious acks on them - nobody elected me as the > arbiter of proper coding style. Hi Jonathan, Thanks! Andrew previously integrated it into mm-nomm and tagged it as [TO-BE-UPDATED] before removing it a few days back. Here's the link: https://lore.kernel.org/mm-commits/20240330025857.CD609C433F1@xxxxxxxxxxxxxxx/ So if feasible, I'd prefer to stick with Andrew's channel. > > A nit below > > Barry Song <21cnbao@xxxxxxxxx> writes: > > > From: Barry Song <v-songbaohua@xxxxxxxx> > > > > Recent commit 77292bb8ca69c80 ("crypto: scomp - remove memcpy if > > sg_nents is 1 and pages are lowmem") leads to warnings on xtensa > > and loongarch, > > In file included from crypto/scompress.c:12: > > include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone': > > include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable] > > 76 | struct page *page; > > | ^~~~ > > crypto/scompress.c: In function 'scomp_acomp_comp_decomp': > >>> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable] > > 174 | struct page *dst_page = sg_page(req->dst); > > | > > > > The reason is that flush_dcache_page() is implemented as a noop > > macro on these platforms as below, > > > > #define flush_dcache_page(page) do { } while (0) > > > > The driver code, for itself, seems be quite innocent and placing > > maybe_unused seems pointless, > > > > struct page *dst_page = sg_page(req->dst); > > > > for (i = 0; i < nr_pages; i++) > > flush_dcache_page(dst_page + i); > > > > And it should be independent of architectural implementation > > differences. > > > > Let's provide guidance on coding style for requesting parameter > > evaluation or proposing the migration to a static inline > > function. > > > > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > > Suggested-by: Max Filippov <jcmvbkbc@xxxxxxxxx> > > Reviewed-by: Mark Brown <broonie@xxxxxxxxxx> > > Cc: Chris Zankel <chris@xxxxxxxxxx> > > Cc: Huacai Chen <chenhuacai@xxxxxxxxxxx> > > Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > > Cc: Guenter Roeck <linux@xxxxxxxxxxxx> > > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > > Cc: Andy Whitcroft <apw@xxxxxxxxxxxxx> > > Cc: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx> > > Cc: Joe Perches <joe@xxxxxxxxxxx> > > Cc: Jonathan Corbet <corbet@xxxxxxx> > > Cc: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx> > > Cc: Xining Xu <mac.xxn@xxxxxxxxxxx> > > --- > > Documentation/process/coding-style.rst | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst > > index 9c7cf7347394..791d333a57fd 100644 > > --- a/Documentation/process/coding-style.rst > > +++ b/Documentation/process/coding-style.rst > > @@ -827,6 +827,22 @@ Macros with multiple statements should be enclosed in a do - while block: > > do_this(b, c); \ > > } while (0) > > > > +Function-like macros with unused parameters should be replaced by static > > +inline functions to avoid the issue of unused variables: > > + > > +.. code-block:: c > > I would just use the "::" notation here; the ..code-block:: just adds > noise IMO. I am not quite sure we want this. as reading the whole coding-style.rst, .. code-block:: c is everywhere :-) Should I do something different or just follow the tradition? > > > + static inline void fun(struct foo *foo) > > + { > > + } > > + > > +For historical reasons, many files still use the cast to (void) to evaluate > > +parameters, but this method is not recommended: > > + > > +.. code-block:: c > > + > > + #define macrofun(foo) do { (void) (foo); } while (0) > > + > > 1) If you're putting in examples of something *not* to do, it's probably > better to also put in something like: > > /* don't do this */ > > people don't always read closely. ok. > > 2) Can we say *why* it's not recommended? > Andrew makes a valid point. https://lore.kernel.org/all/20240321104427.730b859087afecf5973d1c58@xxxxxxxxxxxxxxxxxxxx/ "I think so. My overall view is that we should write things in C. Only use macros if the thing we're trying to do simply cannot be done in a C function. - inline functions don't have the "expression with side effects evaluated more than once" problem. - inline functions avoid the unused-variable issue which started this thread - inline functions look better - for some reason, people are more inclined to document inline functions than macros." Andrew's point seems too lengthy for inclusion in the coding-style.rst document? I'll attempt to condense it. > Thanks, > > jon Thanks Barry
