[PATCH v1] cpufreq: Add defensive checks during driver registration

[PATCH v1] cpufreq: Add defensive checks during driver registration

[Zihuan Zhang]

Currently, cpufreq allows drivers to implement both has_target() and
has_target_index(), which can lead to ambiguous or incorrect behavior.

This patch adds defensive checks in the driver registration path to
prevent invalid implementations. For example, a driver is no longer
allowed to implement both has_target() and has_target_index() at the
same time. These checks help catch driver mistakes early and improve
overall robustness, without affecting existing valid drivers.

Signed-off-by: Zihuan Zhang <zhangzihuan@kylinos.cn>
---
 drivers/cpufreq/cpufreq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index a615c98d80ca..cead6d4fa1ad 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2922,6 +2922,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 		return -EPROBE_DEFER;
 
 	if (!driver_data || !driver_data->verify || !driver_data->init ||
+	     (driver_data->target_index && driver_data->target) ||
 	     (!!driver_data->setpolicy == (driver_data->target_index || driver_data->target)) ||
 	     (!driver_data->get_intermediate != !driver_data->target_intermediate) ||
 	     (!driver_data->online != !driver_data->offline) ||
-- 
2.25.1

Re: [PATCH v1] cpufreq: Add defensive checks during driver registration

[Rafael J. Wysocki]

On Mon, Sep 8, 2025 at 10:57 AM Zihuan Zhang <zhangzihuan@kylinos.cn> wrote:
>
> Currently, cpufreq allows drivers to implement both has_target() and
> has_target_index(), which can lead to ambiguous or incorrect behavior.
>
> This patch adds defensive checks in the driver registration path to
> prevent invalid implementations. For example, a driver is no longer
> allowed to implement both has_target() and has_target_index() at the
> same time. These checks help catch driver mistakes early and improve
> overall robustness, without affecting existing valid drivers.
>
> Signed-off-by: Zihuan Zhang <zhangzihuan@kylinos.cn>
> ---
>  drivers/cpufreq/cpufreq.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index a615c98d80ca..cead6d4fa1ad 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2922,6 +2922,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>                 return -EPROBE_DEFER;
>
>         if (!driver_data || !driver_data->verify || !driver_data->init ||
> +            (driver_data->target_index && driver_data->target) ||
>              (!!driver_data->setpolicy == (driver_data->target_index || driver_data->target)) ||
>              (!driver_data->get_intermediate != !driver_data->target_intermediate) ||
>              (!driver_data->online != !driver_data->offline) ||
> --

Applied as 6.18 material with edits in the subject and changelog, thanks!