linux-kernel - [PATCH] thermal/drivers/exynos_tmu: Fix warnings in temp_to_code / code_to

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Date:   Fri, 13 Apr 2018 13:00:09 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     b.zolnierkie@...sung.com, edubezval@...il.com, rui.zhang@...el.com
Cc:     philip.li@...el.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, daniel.lezcano@...aro.org,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-samsung-soc@...r.kernel.org (open list:SAMSUNG THERMAL DRIVER),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/SAMSUNG EXYNOS
        ARM ARCHITECTURES)
Subject: [PATCH] thermal/drivers/exynos_tmu: Fix warnings in temp_to_code / code_to_temp

The latest driver cleanup introduced a compilation warning

 drivers/thermal/samsung/exynos_tmu.c: In function ‘exynos_get_temp’:
 drivers/thermal/samsung/exynos_tmu.c:931:37: warning: ‘temp’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   *temp = code_to_temp(data, value) * MCELSIUS;
                                        ^

 drivers/thermal/samsung/exynos_tmu.c: In function ‘temp_to_code’
 drivers/thermal/samsung/exynos_tmu.c:304:9: warning: ‘temp_code’ may be used uninitialized in this function [-Wmaybe-uninitialized]
					  return temp_code;
					           ^~~~~~~~~

The compiler gives a warning because semantically speaking the
function has no default value. However the code path, were the
variable is never initialized is a dead branch because the switch
statement always choose one of the two cases as the data->cal_type is
initialized in the init function to one of both values.

This is unclear as it adds a dependency on the initialization function
and it is prone to error. Make things clearer by converting the
functions with if ... return statements, thus showing we are expecting
the values to be correctly filled before calling this function.

This change fixes the couple of function warnings.

Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/thermal/samsung/exynos_tmu.c | 46 ++++++++++--------------------------
 1 file changed, 12 insertions(+), 34 deletions(-)

diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
index 2ec8548..197f267 100644
--- a/drivers/thermal/samsung/exynos_tmu.c
+++ b/drivers/thermal/samsung/exynos_tmu.c
@@ -284,24 +284,13 @@ static void exynos_report_trigger(struct exynos_tmu_data *p)
  */
 static int temp_to_code(struct exynos_tmu_data *data, u8 temp)
 {
-	int temp_code;
-
-	switch (data->cal_type) {
-	case TYPE_TWO_POINT_TRIMMING:
-		temp_code = (temp - EXYNOS_FIRST_POINT_TRIM) *
-			(data->temp_error2 - data->temp_error1) /
-			(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) +
-			data->temp_error1;
-		break;
-	case TYPE_ONE_POINT_TRIMMING:
-		temp_code = temp + data->temp_error1 - EXYNOS_FIRST_POINT_TRIM;
-		break;
-	default:
-		WARN_ON(1);
-		break;
-	}
+	if (data->cal_type == TYPE_ONE_POINT_TRIMMING)
+		return temp + data->temp_error1 - EXYNOS_FIRST_POINT_TRIM;
 
-	return temp_code;
+	return (temp - EXYNOS_FIRST_POINT_TRIM) *
+		(data->temp_error2 - data->temp_error1) /
+		(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) +
+		data->temp_error1;
 }
 
 /*
@@ -310,24 +299,13 @@ static int temp_to_code(struct exynos_tmu_data *data, u8 temp)
  */
 static int code_to_temp(struct exynos_tmu_data *data, u16 temp_code)
 {
-	int temp;
-
-	switch (data->cal_type) {
-	case TYPE_TWO_POINT_TRIMMING:
-		temp = (temp_code - data->temp_error1) *
-			(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) /
-			(data->temp_error2 - data->temp_error1) +
-			EXYNOS_FIRST_POINT_TRIM;
-		break;
-	case TYPE_ONE_POINT_TRIMMING:
-		temp = temp_code - data->temp_error1 + EXYNOS_FIRST_POINT_TRIM;
-		break;
-	default:
-		WARN_ON(1);
-		break;
-	}
+	if (data->cal_type == TYPE_ONE_POINT_TRIMMING)
+		return temp_code - data->temp_error1 + EXYNOS_FIRST_POINT_TRIM;
 
-	return temp;
+	return (temp_code - data->temp_error1) *
+		(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) /
+		(data->temp_error2 - data->temp_error1) +
+		EXYNOS_FIRST_POINT_TRIM;
 }
 
 static void sanitize_temp_error(struct exynos_tmu_data *data, u32 trim_info)
-- 
2.7.4