Re: [cocci] [PATCH] coccinelle: Detect clk_register() anti-pattern

On Sun, 2 Aug 2026, Guru Das Srinagesh wrote:

> Enforce commit 12a0fd23e870 ("clk: Print an error when clk registration
> fails"): clk_register(), clk_hw_register(), and their devm_/of_ variants
> log their own error on failure, so driver-side error prints after these
> calls are redundant.
>
> Two independent match families, one per return-value convention:
> pointer return checked via IS_ERR() (clk_register()/devm_clk_register()),
> and int return checked via a nonzero value (clk_hw_register()/
> devm_clk_hw_register()/of_clk_hw_register()).
>
> Assisted-by: Claude:claude-sonnet-5 coccinelle
> Signed-off-by: Guru Das Srinagesh <[email protected]>
> ---
> Add a Coccinelle semantic patch enforcing commit 12a0fd23e870 ("clk:
> Print an error when clk registration fails"): flags, and in "patch"
> mode removes, driver-side error prints that are now redundant after
> clk_register()/clk_hw_register() and their devm_/of_ variants.
>
> Two independent match families, one per return-value convention.
>
> Pointer return, IS_ERR()-checked (clk_register()/devm_clk_register()),
> e.g. drivers/clk/clk-xgene.c:152-157:
>
>     clk = clk_register(dev, &apmclk->hw);
>     if (IS_ERR(clk)) {
> -       pr_err("%s: could not register clk %s\n", __func__, name);
>         kfree(apmclk);
>         return NULL;
>     }
>
> Int return, nonzero-checked (clk_hw_register()/devm_clk_hw_register()/
> of_clk_hw_register()), e.g. drivers/clk/meson/meson-clkc-utils.c:49-54:
>
>     ret = devm_clk_hw_register(dev, hw);
>     if (ret) {
> -       dev_err(dev, "registering %s clock failed\n",
> -               hw->init->name);
>         return ret;
>     }
>
> Testing:
> - Baseline: coccinelle 1.3.1, the Torvalds tree at v7.2-rc5.
> - "make coccicheck COCCI=<path> MODE=report M=drivers/clk" produced 73
>   hits and verified to have zero false positives.
> - "MODE=patch" verified separately on scratch copies of affected files
>   to confirm minimal, correct diffs.
>
> checkpatch flagged that this new file needs a MAINTAINERS entry, and I'd

I don't have an opinion about this.  If you want to be responsible for it
that's fine with me.

> like to maintain it, so this adds a standalone entry rather than leaving
> the file uncovered. There's no direct precedent for an individual .cocci
> file getting its own entry - the only other named .cocci file in
> MAINTAINERS, scripts/coccinelle/api/string_choices.cocci, was added to
> the existing GENERIC STRING LIBRARY entry by that subsystem's
> maintainer, not as a new one. Happy to fold this into COMMON CLK
> FRAMEWORK or drop it entirely depending on what the maintainers prefer.
> ---
>  MAINTAINERS                               |   5 ++
>  scripts/coccinelle/api/clk_register.cocci | 125 ++++++++++++++++++++++++++++++
>  2 files changed, 130 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 716acfc3d7c1..26788ccbf98c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6363,6 +6363,11 @@ L:	[email protected]
>  S:	Maintained
>  F:	include/linux/clk.h
>
> +CLK_REGISTER() COCCINELLE CHECK
> +M:	Guru Das Srinagesh <[email protected]>
> +S:	Maintained
> +F:	scripts/coccinelle/api/clk_register.cocci
> +
>  CLOCKSOURCE, CLOCKEVENT DRIVERS
>  M:	Daniel Lezcano <[email protected]>
>  M:	Thomas Gleixner <[email protected]>
> diff --git a/scripts/coccinelle/api/clk_register.cocci b/scripts/coccinelle/api/clk_register.cocci
> new file mode 100644
> index 000000000000..fe5bcd4b00d4
> --- /dev/null
> +++ b/scripts/coccinelle/api/clk_register.cocci
> @@ -0,0 +1,125 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/// Remove error messages after clk registration failures, because
> +/// clk_register(), clk_hw_register(), and their variants already log
> +/// an error when they fail. See commit 12a0fd23e870 ("clk: Print an
> +/// error when clk registration fails").
> +//
> +// Confidence: Medium
> +// Options: --include-headers
> +
> +virtual patch
> +virtual context
> +virtual org
> +virtual report
> +
> +@depends on context@
> +expression clk;
> +identifier reg =~ "^(devm_)?clk_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +clk = reg(...);

From a performance point of view, it would be desirable to put instead
\(devm_clk_register\|clk_register\).  This will trigger some
optimizations that won't be triggered by a regular expression.


> +if ( \( IS_ERR(clk) \| IS_ERR(clk) == 1 \) )
> +{
> +...
> +*voidfn(...);
> +...
> +}
> +
> +@depends on patch@
> +expression clk;
> +identifier reg =~ "^(devm_)?clk_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +clk = reg(...);
> +if ( \( IS_ERR(clk) \| IS_ERR(clk) == 1 \) )
> +{
> +...
> +-voidfn(...);
> +...
> +}
> +
> +@r1 depends on org || report@
> +position p1;
> +expression clk;
> +identifier reg =~ "^(devm_)?clk_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +clk = reg(...);
> +if ( \( IS_ERR(clk) \| IS_ERR(clk) == 1 \) )
> +{
> +...
> +voidfn@p1(...);
> +...
> +}
> +
> +@depends on context@
> +expression ret;
> +identifier reg =~ "^(devm_)?(of_)?clk_hw_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +ret = reg(...);
> +if ( \( ret \| ret != 0 \| ret < 0 \) )
> +{
> +...
> +*voidfn(...);
> +...
> +}
> +
> +@depends on patch@
> +expression ret;
> +identifier reg =~ "^(devm_)?(of_)?clk_hw_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +ret = reg(...);
> +if ( \( ret \| ret != 0 \| ret < 0 \) )
> +{
> +...
> +-voidfn(...);
> +...
> +}

I think yourpatch rule should have an extra case for where there are
currently only two statements in the if branch.  In that case the {}
should be removed.

julia

> +
> +@r2 depends on org || report@
> +position p2;
> +expression ret;
> +identifier reg =~ "^(devm_)?(of_)?clk_hw_register$";
> +identifier voidfn =~ "^(dev_err|dev_warn|pr_err|pr_warn)$";
> +@@
> +
> +ret = reg(...);
> +if ( \( ret \| ret != 0 \| ret < 0 \) )
> +{
> +...
> +voidfn@p2(...);
> +...
> +}
> +
> +@script:python depends on org@
> +p1 << r1.p1;
> +@@
> +
> +cocci.print_main(p1)
> +
> +@script:python depends on report@
> +p1 << r1.p1;
> +@@
> +
> +msg = "line %s is redundant because clk_register() already prints an error on failure" % (p1[0].line)
> +coccilib.report.print_report(p1[0], msg)
> +
> +@script:python depends on org@
> +p2 << r2.p2;
> +@@
> +
> +cocci.print_main(p2)
> +
> +@script:python depends on report@
> +p2 << r2.p2;
> +@@
> +
> +msg = "line %s is redundant because clk_hw_register() already prints an error on failure" % (p2[0].line)
> +coccilib.report.print_report(p2[0], msg)
>
> ---
> base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
> change-id: 20260802-cocci-clk-register-951d94251af4
>
> Best regards,
> --
> Guru Das Srinagesh <[email protected]>
>
>