linux-kernel - Re: [PATCH v8 05/16] ACPI: processor: Add acpi_get_processor

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Date: Tue, 30 Apr 2024 14:26:06 +1000
From: Gavin Shan <gshan@...hat.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra <peterz@...radead.org>,
 linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 kvmarm@...ts.linux.dev, x86@...nel.org, Russell King
 <linux@...linux.org.uk>, "Rafael J . Wysocki" <rafael@...nel.org>,
 Miguel Luis <miguel.luis@...cle.com>, James Morse <james.morse@....com>,
 Salil Mehta <salil.mehta@...wei.com>,
 Jean-Philippe Brucker <jean-philippe@...aro.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Marc Zyngier <maz@...nel.org>, Hanjun Guo <guohanjun@...wei.com>
Cc: Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, linuxarm@...wei.com,
 justin.he@....com, jianyong.wu@....com,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v8 05/16] ACPI: processor: Add acpi_get_processor_handle()
 helper

On 4/26/24 23:51, Jonathan Cameron wrote:
> If CONFIG_ACPI_PROCESSOR provide a helper to retrieve the
> acpi_handle for a given CPU allowing access to methods
> in DSDT.
> 
> Tested-by: Miguel Luis <miguel.luis@...cle.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 
> ---
> v8: Code simplification suggested by Rafael.
>      Fixup ;; spotted by Gavin
> ---
>   drivers/acpi/acpi_processor.c | 11 +++++++++++
>   include/linux/acpi.h          |  7 +++++++
>   2 files changed, 18 insertions(+)
> 

Reviewed-by: Gavin Shan <gshan@...hat.com>

> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 3b180e21f325..ecc2721fecae 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -35,6 +35,17 @@ EXPORT_PER_CPU_SYMBOL(processors);
>   struct acpi_processor_errata errata __read_mostly;
>   EXPORT_SYMBOL_GPL(errata);
>   
> +acpi_handle acpi_get_processor_handle(int cpu)
> +{
> +	struct acpi_processor *pr;
> +
> +	pr = per_cpu(processors, cpu);
> +	if (pr)
> +		return pr->handle;
> +
> +	return NULL;
> +}
> +

Maybe it's worthy to have more check here, something like below.
However, it's also fine without the extra check.

	if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
		return NULL;

>   static int acpi_processor_errata_piix4(struct pci_dev *dev)
>   {
>   	u8 value1 = 0;
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 34829f2c517a..9844a3f9c4e5 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -309,6 +309,8 @@ int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 acpi_id,
>   int acpi_unmap_cpu(int cpu);
>   #endif /* CONFIG_ACPI_HOTPLUG_CPU */
>   
> +acpi_handle acpi_get_processor_handle(int cpu);
> +
>   #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
>   int acpi_get_ioapic_id(acpi_handle handle, u32 gsi_base, u64 *phys_addr);
>   #endif
> @@ -1077,6 +1079,11 @@ static inline bool acpi_sleep_state_supported(u8 sleep_state)
>   	return false;
>   }
>   
> +static inline acpi_handle acpi_get_processor_handle(int cpu)
> +{
> +	return NULL;
> +}
> +
>   #endif	/* !CONFIG_ACPI */
>   
>   extern void arch_post_acpi_subsys_init(void);

Thanks,
Gavin