linux-kernel - [PATCH v1 1/2] perf/core: Add API to look up PMU type by name

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Date:   Fri, 23 Feb 2018 16:19:37 -0800
From:   Saravana Kannan <skannan@...eaurora.org>
To:     mark.rutland@....com, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Cc:     skannan@...eaurora.org, avilaj@...eaurora.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/2] perf/core: Add API to look up PMU type by name

When the event numbers registered by multiple PMUs overlap, the
attr->type value passed to perf_event_create_kernel_counter() is used
to determine which PMU to use to create a perf_event.

However, when the PMU in question is not a standard PMU (defined in
perf_type_id), there is no way for a kernel client to look up the PMU
type for the PMU of interest and set the attr->type appropriately.

So, add an API to look up the PMU type by name. That way, the kernel
APIs can function in a fashion similar to the user space interface.

Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
---
 kernel/events/core.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 96db9ae..5d3df58 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10310,6 +10310,29 @@ static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
 	return err;
 }
 
+int perf_find_pmu_type_by_name(const char *name)
+{
+	struct pmu *pmu;
+	int ret = -1;
+
+	mutex_lock(&pmus_lock);
+
+	list_for_each_entry(pmu, &pmus, entry) {
+		if (!pmu->name || pmu->type < 0)
+			continue;
+
+		if (!strcmp(name, pmu->name)) {
+			ret = pmu->type;
+			goto out;
+		}
+	}
+
+out:
+	mutex_unlock(&pmus_lock);
+
+	return ret;
+}
+
 /**
  * perf_event_create_kernel_counter
  *
-- 
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