linux-kernel - Re: [PATCH 2/7] perf tools: apply evsel__set_config_if

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Message-ID: <6661f623-0b27-429d-92ee-785caf04e682@linaro.org>
Date: Thu, 4 Dec 2025 10:55:30 +0000
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>,
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/7] perf tools: apply evsel__set_config_if_unset() to all
 config fields



On 02/12/2025 11:14 am, Leo Yan wrote:
> On Mon, Dec 01, 2025 at 04:41:05PM +0000, Coresight ML wrote:
> 
> [...]
> 
>>   void evsel__set_config_if_unset(struct perf_pmu *pmu, struct evsel *evsel,
>>   				const char *config_name, u64 val)
>>   {
>>   	u64 user_bits = 0, bits;
>> -	struct evsel_config_term *term = evsel__get_config_term(evsel, USR_CHG_CONFIG);
>> +	struct evsel_config_term *term;
>> +	struct perf_pmu_format *format = pmu_find_format(&pmu->format, config_name);
>> +	__u64 *vp;
> 
> Should check (format == NULL) here and bail out for a unknown config name?
> 

Good point, yes I'll return without any errors. It will be slightly 
inconsistent with the other config functions that return an error if 
it's not found, but it's consistent with the existing function which is 
a nop in that case.

>> +
>> +	switch (format->value) {
>> +	case PERF_PMU_FORMAT_VALUE_CONFIG:
>> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG);
>> +		vp = &evsel->core.attr.config;
>> +		break;
>> +	case PERF_PMU_FORMAT_VALUE_CONFIG1:
>> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG1);
>> +		vp = &evsel->core.attr.config1;
>> +		break;
>> +	case PERF_PMU_FORMAT_VALUE_CONFIG2:
>> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG2);
>> +		vp = &evsel->core.attr.config2;
>> +		break;
>> +	case PERF_PMU_FORMAT_VALUE_CONFIG3:
>> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG3);
>> +		vp = &evsel->core.attr.config3;
>> +		break;
>> +	case PERF_PMU_FORMAT_VALUE_CONFIG4:
>> +		term = evsel__get_config_term(evsel, USR_CHG_CONFIG4);
>> +		vp = &evsel->core.attr.config4;
>> +		break;
>> +	default:
>> +		pr_err("Unknown format value: %d\n", format->value);
>> +		return;
>> +	}
>>   
>>   	if (term)
>>   		user_bits = term->val.cfg_chg;
>> @@ -1396,20 +1436,8 @@ void evsel__set_config_if_unset(struct perf_pmu *pmu, struct evsel *evsel,
>>   		return;
>>   
>>   	/* Otherwise replace it */
>> -	evsel->core.attr.config &= ~bits;
>> -	evsel->core.attr.config |= field_prep(bits, val);
>> -}
>> -
>> -static struct perf_pmu_format *
>> -pmu_find_format(const struct list_head *formats, const char *name)
>> -{
>> -	struct perf_pmu_format *format;
>> -
>> -	list_for_each_entry(format, formats, list)
>> -		if (!strcmp(format->name, name))
>> -			return format;
>> -
>> -	return NULL;
>> +	*vp &= ~bits;
>> +	*vp |= FIELD_PREP(bits, val);
>>   }