linux-kernel - Re: [PATCH v2 1/3] selftests/resctrl: Add CPU vendor detection for Hygon

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Message-ID: <d28d3e39-3f09-4187-934a-19b71ce188cc@open-hieco.net>
Date: Wed, 10 Dec 2025 12:46:48 +0800
From: Xiaochen Shen <shenxiaochen@...n-hieco.net>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Fenghua Yu <fenghuay@...dia.com>, tony.luck@...el.com, bp@...en8.de,
 shuah@...nel.org, skhan@...uxfoundation.org
Cc: babu.moger@....com, james.morse@....com, Dave.Martin@....com,
 x86@...nel.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, shenxiaochen@...n-hieco.net
Subject: Re: [PATCH v2 1/3] selftests/resctrl: Add CPU vendor detection for
 Hygon

Hi Reinette,

On 12/10/2025 7:02 AM, Reinette Chatre wrote:
> I suggest this be simplified to not have the vendor ID be used both as a value and as a state.
> Here is some pseudo-code that should be able to accomplish this:
> 
> 
> 	unsigned int detect_vendor(void)
> 	{
> 		static bool initialized = false;
> 		static unsigned int vendor_id;
> 		...
> 		FILE *inf;
> 
> 
> 		if (initialized)
> 			return vendor_id;
> 
> 		inf = fopen("/proc/cpuinfo", "r");
> 		if (!inf) {
> 			vendor_id = 0;
> 			initialized = true;
> 			return vendor_id;
> 		}
> 
> 		/* initialize vendor_id from /proc/cpuinfo */
> 
> 		initialized = true;
> 		return vendor_id;
> 	}
> 
> 	unsigned int get_vendor(void)
> 	{
> 		unsigned int vendor;
> 		
> 		vendor = detect_vendor();
> 
> 		if (vendor == 0)
> 			ksft_print_msg(...);
> 
> 		return vendor;
> 	}
> 
> Reinette


Thank you very much! I will make the change in v3 patch series.

Could you help review the revised patch description for the change?
--------------------------------
    ...
    and makes it obvious when adding new vendor IDs.

    Accordingly, update the return types of detect_vendor() and get_vendor()
    from 'int' to 'unsigned int' to align with their usage as bitmask values
    and to prevent potentially risky type conversions.

    Furthermore, introduce a bool flag 'initialized' to simplify the
    get_vendor() -> detect_vendor() logic. This ensures the vendor ID is
    detected only once and resolves the ambiguity of using the same variable
    'vendor' both as a value and as a state.

--------------------------------

Thank you!
 
Best regards,
Xiaochen Shen