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

[Joel Granados]

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

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@xxxxxxxxx wrote:
> > From: Wen Yang <wen.yang@xxxxxxxxx>
> > 
> > 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@xxxxxxxxx/
> > 
> > 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(-)
> > 

-- 

Joel Granados

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