linux-kernel - Re: [PATCH v4 1/6] ACPI: CPPC: Add IS_OPTIONAL_CPC

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Message-ID: <CAJZ5v0ja7AaJza0PeNgutebXRV3tsgxZRwZUBcFksD9thyKg1Q@mail.gmail.com>
Date: Tue, 14 Jan 2025 14:27:12 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lifeng Zheng <zhenglifeng1@...wei.com>
Cc: rafael@...nel.org, lenb@...nel.org, robert.moore@...el.com, 
	viresh.kumar@...aro.org, mario.limonciello@....com, gautham.shenoy@....com, 
	ray.huang@....com, pierre.gondois@....com, acpica-devel@...ts.linux.dev, 
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-pm@...r.kernel.org, linuxarm@...wei.com, jonathan.cameron@...wei.com, 
	zhanjie9@...ilicon.com, lihuisong@...wei.com, hepeng68@...wei.com, 
	fanghao11@...wei.com
Subject: Re: [PATCH v4 1/6] ACPI: CPPC: Add IS_OPTIONAL_CPC_REG macro

On Mon, Jan 13, 2025 at 1:21 PM Lifeng Zheng <zhenglifeng1@...wei.com> wrote:
>
> Add IS_OPTIONAL_CPC_REG macro to judge if a cpc_reg is an optional one.

This requires a bit more explanation, especially what's the purpose of
it (ie. the "why").

> Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
> ---
>  drivers/acpi/cppc_acpi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index f193e713825a..6454b469338f 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -129,6 +129,12 @@ static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);
>  #define CPC_SUPPORTED(cpc) ((cpc)->type == ACPI_TYPE_INTEGER ?         \
>                                 !!(cpc)->cpc_entry.int_value :          \
>                                 !IS_NULL_REG(&(cpc)->cpc_entry.reg))
> +
> +/* These indicate optional of the per-cpu cpc_regs[]. */

Again, you need to say more here, like how this is supposed to work.

> +#define REG_OPTIONAL (0b111111100011111010000)

A hex literal would work too AFAICS.

> +
> +#define IS_OPTIONAL_CPC_REG(reg_idx) (REG_OPTIONAL & (1U << (reg_idx)))

You need to explain what reg_idx is.

> +
>  /*
>   * Arbitrary Retries in case the remote processor is slow to respond
>   * to PCC commands. Keeping it high enough to cover emulators where
> --