mcp23018: add return status to init (#18178)

drivers/gpio/mcp23018.c

@@ -18,14 +18,20 @@ enum {
     CMD_GPIOB  = 0x13,
 };
 
-void mcp23018_init(uint8_t addr) {
+bool mcp23018_init(uint8_t slave_addr) {
     static uint8_t s_init = 0;
-    if (!s_init) {
+    uint8_t        addr   = SLAVE_TO_ADDR(slave_addr);
+    if (0 == s_init) {
         i2c_init();
-        wait_ms(1000);
+        wait_ms(100);
 
-        s_init = 1;
+        // probe that the expander is actually connected by reading from it
+        uint8_t data = 0;
+        if (I2C_STATUS_SUCCESS == i2c_readReg(addr, 0, &data, sizeof(data), 150)) {
+            s_init = 1;
+        }
     }
+    return (s_init > 0);
 }
 
 bool mcp23018_set_config(uint8_t slave_addr, mcp23018_port_t port, uint8_t conf) {

drivers/gpio/mcp23018.h

@@ -33,7 +33,7 @@ enum {
 /**
  * Init expander and any other dependent drivers
  */
-void mcp23018_init(uint8_t slave_addr);
+bool mcp23018_init(uint8_t slave_addr);
 
 /**
  * Configure input/output to a given port