LM75 bug fix for negative temperatures

When the LM75 temperature sensor measures a temperature below 0 C, the current driver does not perform sign extension, so the result returned is 256 C too high. This patch fixes the problem. Signed-off-by: Larry Johnson <lrj@acm.org>

LM75 bug fix for negative temperatures
When the LM75 temperature sensor measures a temperature below 0 C, the current driver does not perform sign extension, so the result returned is 256 C too high. This patch fixes the problem. Signed-off-by: Larry Johnson <lrj@acm.org>
Larry Johnson · Wolfgang Denk
1 parent 5a910c224b
Showing 1 changed file with 7 additions and 1 deletions Side-by-side Diff
drivers/hwmon/lm75.c
@@ -179,7 +179,13 @@
  
 int dtt_get_temp(int sensor)
 {
-    return (dtt_read(sensor, DTT_READ_TEMP) / 256);
+    int const ret = dtt_read(sensor, DTT_READ_TEMP);
+
+    if (ret < 0) {
+	printf("DTT temperature read failed.\n");
+	return 0;
+    }
+    return (int)((int16_t) ret / 256);
 } /* dtt_get_temp() */
  
 #endif /* CONFIG_DTT_LM75 */
...	...	@@ -179,7 +179,13 @@
179	179
180	180	int dtt_get_temp(int sensor)
181	181	{
182		- return (dtt_read(sensor, DTT_READ_TEMP) / 256);
	182	+ int const ret = dtt_read(sensor, DTT_READ_TEMP);
	183	+
	184	+ if (ret < 0) {
	185	+ printf("DTT temperature read failed.\n");
	186	+ return 0;
	187	+ }
	188	+ return (int)((int16_t) ret / 256);
183	189	} /* dtt_get_temp() */
184	190
185	191	#endif /* CONFIG_DTT_LM75 */