Re: [RFC PATCH v5 0/2] sysctl: add CTLTBL_ENTRY_XXX() macros for ctl_table initialization

[Joel Granados <joel.granados@kernel.org>]

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On Sun, Oct 25, 2026 at 12:43:37AM +0800, Wen Yang wrote:
> 
> 
> On 6/17/26 23:25, Joel Granados wrote:
> > Hey Wen
> > 
> > Sorry for not getting back to you sooner.
> > 
> > IMO, this is approach is the way to go to bring back the control of the
> > sysctl variables into the sysctl subsys files. Would like to get another
> > set of eyes on it before committing to it though.
> > 
> > I think it has not gotten too much attention because it does not touch
> > any other subsystem. Would you consider adding one subsys to the series?
> > Something like implementing it for the users in arch/ or fs/ or
> > drivers/.
> > 
> > Also, this might be a signal to park this temporarily and let it simmer
> > until more ppl are annoyed at making changes to the sysctl API.
> > 
> > Best
> > 
> 
> Hi Joel,
> 
> Apologies for the long delay, and thank you for your helpful feedback.
> 
> I've been tied up with other commitments, but can now return to this
> 
> work and prepare v3 based on your suggestions.
> 
> 
> 
> Given the time that has passed, I'd appreciate any updated advice or
> 
> related developments I should take into account.

There is now more clarity that the use of MACROS like we had discussed
for this series is probably not the way to go. In [1] it is clear that
the overuse of macros will probably be rejected once it gets upstream.
So for now I would let this implementation go.

Best

[1] https://lore.kernel.org/all/CAHk-=wjUmLrJd4KM4xvJHUN4P0r8oSu5LyvG4JipnhxizBrE9Q@mail.gmail.com
> 
> 
> 
> Thanks again for your time and patience.
> 
> 
> -- 
> 
> Best regards,                                                            Wen
> 
> > On Sat, Jun 13, 2026 at 11:56:50PM +0800, Wen Yang wrote:
> > > Hi Kees, H jioel,
> > > 
> > > Gentle ping on this series. Please let me know if there are any
> > > concerns or if further changes are needed.
> > > 
> > > The series is available at:
> > > https://lore.kernel.org/all/x5stdwwsfp2h22zyexn5ycbxnkyc4ioxscninxsa6q7lf6djqr@jkuppwwqubkp/
> > > 
> > > Thanks for your time,
> > > Wen
> > > 
> > > 
> > > On 3/26/26 02:39, wen.yang@linux.dev wrote:
> > > > From: Wen Yang <wen.yang@linux.dev>
> > > > 
> > > > Historically, changes to how struct ctl_table entries are initialized
> > > > (e.g. removing the child field, const-qualifying ctl_table) required
> > > > touching hundreds of files across all subsystems.  Such series require
> > > > the attention of many maintainers, sometimes need to be pulled into
> > > > mainline in a special way, and create lots of unnecessary churn.  With
> > > > CTLTBL_ENTRY_XXX(), future structural changes to struct ctl_table need
> > > > only update the macro definitions.
> > > > 
> > > > Conversion of existing call sites will proceed incrementally from
> > > > kernel/sysctl.c outward, rather than as a treewide sweep.
> > > > 
> > > > This series:
> > > >    1. Introduces the CTLTBL_ENTRY_XXX() macros in include/linux/sysctl.h,
> > > >       using _Generic() for automatic proc_handler selection, auto
> > > >       address-of, auto maxlen via sizeof(), and compile-time validation.
> > > >       Supported types: int, unsigned int, long, unsigned long, bool, u8.
> > > >    2. Converts kernel/sysctl-test.c as a demonstration, adding a
> > > >       parameterized KUnit test covering all macro variants (V, VM, VMR,
> > > >       VN, VNM, VNMH) across int, u8, bool, and char[] types.
> > > > 
> > > > Based on discussion and suggestions from:
> > > > [1] https://sysctl-dev-rtd.readthedocs.io/en/latest/notes/ctltable_entry_macro.html
> > > > [2] https://lore.kernel.org/all/psot4oeauxi3yyj2w4ajm3tfgtcsvao4rhv5sgd5s6ymmjgojk@p3vrj3qluban/
> > > > 
> > > > ---
> > > > Changes in v5:
> > > >     - Extend __CTL_AUTO_HANDLER to support bool and u8
> > > >     - Replace individual test functions with a single parameterized KUnit
> > > >       test (KUNIT_CASE_PARAM) covering all variants and types
> > > >     - Use struct ctl_table as the expected-value container in the param
> > > >       struct, eliminating custom expected_* fields
> > > > 
> > > > Changes in v4:
> > > >     - Fix Wpointer-type-mismatch warnings detected by lkp:
> > > >       https://lore.kernel.org/oe-kbuild-all/202603050724.SZxrEyyu-lkp@intel.com/
> > > > 
> > > > Changes in v3:
> > > >     - Replace the unique macro with "capital letter approach"
> > > >     - Reduce the name further
> > > >     https://lore.kernel.org/all/rn4rsazh7kxf5byq65vw2phyqgzvwm3scczu3l5h2r4aqit2r6@znlpb24z2zuo/
> > > > 
> > > > Changes in v2:
> > > >     - Add lvalue check, handler type check, etc.
> > > >     https://lore.kernel.org/all/xptwb3uwbzposd4xf7khj52ifv4tchcjdgllhv7aabi6d7wgef@2msurl564v53/
> > > > 
> > > > 
> > > > Wen Yang (2):
> > > >     sysctl: introduce CTLTBL_ENTRY_XXX() helper macros
> > > >     sysctl: convert kernel/sysctl-test.c to use CTLTBL_ENTRY_XXX()
> > > > 
> > > >    include/linux/sysctl.h | 307 +++++++++++++++++++++++++++++++++++++++++
> > > >    kernel/sysctl-test.c   | 237 ++++++++++++++++++-------------
> > > >    kernel/sysctl.c        |   2 +
> > > >    3 files changed, 447 insertions(+), 99 deletions(-)
> > > > 
> > 

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