HID: simplify snto32()

snto32() does exactly what sign_extend32() does, but handles
potentially malformed data coming from the device. Keep the checks,
but then call sign_extend32() to perform the actual conversion.

Signed-off-by: Dmitry Torokhov <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Benjamin Tissoires <[email protected]>

Author: dtor

drivers/hid/hid-core.c

@@ -1313,9 +1313,7 @@ int hid_open_report(struct hid_device *device)
 EXPORT_SYMBOL_GPL(hid_open_report);
 
 /*
- * Convert a signed n-bit integer to signed 32-bit integer. Common
- * cases are done through the compiler, the screwed things has to be
- * done by hand.
+ * Convert a signed n-bit integer to signed 32-bit integer.
  */
 
 static s32 snto32(__u32 value, unsigned n)
@@ -1326,12 +1324,7 @@ static s32 snto32(__u32 value, unsigned n)
 	if (n > 32)
 		n = 32;
 
-	switch (n) {
-	case 8:  return ((__s8)value);
-	case 16: return ((__s16)value);
-	case 32: return ((__s32)value);
-	}
-	return value & (1 << (n - 1)) ? value | (~0U << n) : value;
+	return sign_extend32(value, n - 1);
 }
 
 s32 hid_snto32(__u32 value, unsigned n)