sensors: detect SmartSens SC1135 by 0x3008/0x3005

src/sensors.c

@@ -468,6 +468,17 @@ static int detect_onsemi_sensor(sensor_ctx_t *ctx, int fd,
     return sid;
 }
 
+// SC1135 holds no ID in 0x3107/0x3108; it is told by 0x3008 = 0x60 and
+// 0x3005 = 0x22. That is the pair the Xiongmai XM510 isp daemon accepts as an
+// SC1135 once 0x3107/0x3108 matched none of its IDs: a sweep of every 0x3005
+// value with 0x3008 = 0x60 under emulation accepted 0x22 alone. The reads are
+// 16-bit addressed, which an 8-bit device takes as a register write, so they
+// are made only when 0x3107/0x3108 read empty.
+static bool is_smartsens_sc1135(int fd, unsigned char i2c_addr) {
+    return i2c_read_register(fd, i2c_addr, 0x3008, 2, 1) == 0x60 &&
+           i2c_read_register(fd, i2c_addr, 0x3005, 2, 1) == 0x22;
+}
+
 static int detect_smartsens_sensor(sensor_ctx_t *ctx, int fd,
                                    unsigned char i2c_addr) {
     if (i2c_change_addr(fd, i2c_addr) < 0)
@@ -483,8 +494,6 @@ static int detect_smartsens_sensor(sensor_ctx_t *ctx, int fd,
     if (lower == -1)
         return false;
 
-    // check for SC1035, SC1145, SC1135 '0x3008' reg val is equal to 0x60
-
     int res = high << 8 | lower;
     switch (res) {
     case 0x0010:
@@ -709,7 +718,11 @@ static int detect_smartsens_sensor(sensor_ctx_t *ctx, int fd,
         return true;
     case 0:
     case 0xffff:
-        // SC1135 catches here
+        // SC1135 has no ID here; only then are two more registers read
+        if (is_smartsens_sc1135(fd, i2c_addr)) {
+            strcpy(ctx->sensor_id, "SC1135");
+            return true;
+        }
         return false;
     default:
         SENSOR_ERR("SmartSens", res);

src/sensors_golden.txt

@@ -63,6 +63,7 @@ smartsens da23 SC1345
 smartsens da4d SC1346
 smartsens dc42 SC4336
 smartsens eb2c SC2355
+smartsens-sc1135 6022 SC1135
 soi 0500 JXK00
 soi 0501 JXK01
 soi 0502 JXK02

src/sensors_test.c

@@ -139,6 +139,14 @@ static void sc_smartsens(uint32_t id) {
     mock_set(0x3107, 2, 1, id >> 8);
     mock_set(0x3108, 2, 1, id & 0xff);
 }
+/* SC1135 has no ID in 0x3107/0x3108: they read empty, and 0x3008/0x3005
+ * name it. */
+static void sc_smartsens_sc1135(uint32_t id) {
+    mock_set(0x3107, 2, 1, 0x00);
+    mock_set(0x3108, 2, 1, 0x00);
+    mock_set(0x3008, 2, 1, id >> 8);
+    mock_set(0x3005, 2, 1, id & 0xff);
+}
 static void sc_soi(uint32_t id) {
     mock_set(0x0a, 1, 1, id >> 8);
     mock_set(0x0b, 1, 1, id & 0xff);
@@ -221,6 +229,7 @@ static void sc_techpoint(uint32_t id) {
 
 static const struct scenario scenarios[] = {
     {"smartsens", detect_smartsens_sensor, sc_smartsens},
+    {"smartsens-sc1135", detect_smartsens_sensor, sc_smartsens_sc1135},
     {"soi", detect_soi_sensor, sc_soi},
     {"onsemi", detect_onsemi_sensor, sc_onsemi},
     {"omni", detect_omni_sensor, sc_omni},