linux-kernel - Re: [PATCH v1 7/9] ACPI: processor: idle: Remove died codes about the verification of cstate count

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Message-ID: <CAJZ5v0j4F5fPwhKup768EUdgWfUHXATiK0zuNwK2fJyC2fqy2A@mail.gmail.com>
Date: Tue, 21 Oct 2025 21:51:30 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Huisong Li <lihuisong@...wei.com>
Cc: rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Sudeep.Holla@....com, linuxarm@...wei.com, 
	jonathan.cameron@...wei.com, zhanjie9@...ilicon.com, zhenglifeng1@...wei.com, 
	yubowen8@...wei.com
Subject: Re: [PATCH v1 7/9] ACPI: processor: idle: Remove died codes about the
 verification of cstate count

On Mon, Sep 29, 2025 at 11:38 AM Huisong Li <lihuisong@...wei.com> wrote:
>
> The acpi_processor_setup_cstates and acpi_processor_setup_cpuidle_cx will
> be called after successfully obtaining the power information. These setup
> functions have their own main role, but also verify the validity of cstate
> count.
>
> Actually, the acpi_processor_get_power_info_cst() will return failure
> if the cstate count is zero and acpi_processor_get_power_info() will return
> failure.
>
> So the verification of cstate count in these functions are died code.

It is useless overhead rather because the conditions checked cannot be true.

> Signed-off-by: Huisong Li <lihuisong@...wei.com>
> ---
>  drivers/acpi/processor_idle.c | 22 +++++++---------------
>  1 file changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 92b231f5d514..2d672afc7498 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -732,8 +732,8 @@ static int __cpuidle acpi_idle_enter_s2idle(struct cpuidle_device *dev,
>         return 0;
>  }
>
> -static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
> -                                          struct cpuidle_device *dev)
> +static void acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
> +                                           struct cpuidle_device *dev)
>  {
>         int i, count = ACPI_IDLE_STATE_START;
>         struct acpi_processor_cx *cx;
> @@ -753,14 +753,9 @@ static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
>                 if (count == CPUIDLE_STATE_MAX)
>                         break;
>         }
> -
> -       if (!count)
> -               return -EINVAL;
> -
> -       return 0;
>  }
>
> -static int acpi_processor_setup_cstates(struct acpi_processor *pr)
> +static void acpi_processor_setup_cstates(struct acpi_processor *pr)
>  {
>         int i, count;
>         struct acpi_processor_cx *cx;
> @@ -822,11 +817,6 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)
>         }
>
>         drv->state_count = count;
> -
> -       if (!count)
> -               return -EINVAL;
> -
> -       return 0;
>  }
>
>  static inline void acpi_processor_cstate_first_run_checks(void)
> @@ -1246,7 +1236,8 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
>         if (pr->flags.has_lpi)
>                 return acpi_processor_setup_lpi_states(pr);
>
> -       return acpi_processor_setup_cstates(pr);
> +       acpi_processor_setup_cstates(pr);
> +       return 0;
>  }
>
>  /**
> @@ -1266,7 +1257,8 @@ static int acpi_processor_setup_cpuidle_dev(struct acpi_processor *pr,
>         if (pr->flags.has_lpi)
>                 return 0;
>
> -       return acpi_processor_setup_cpuidle_cx(pr, dev);
> +       acpi_processor_setup_cpuidle_cx(pr, dev);
> +       return 0;
>  }
>
>  static int acpi_processor_get_power_info(struct acpi_processor *pr)
> --
> 2.33.0
>