eeprom: check I2C (n)ack on read/write

libboard_zynq/src/i2c/eeprom.rs

@@ -51,11 +51,17 @@ impl<'a> EEPROM<'a> {
         self.select()?;
 
         self.i2c.start()?;
-        self.i2c.write(self.address << 1)?;
+        if !self.i2c.write(self.address << 1)? {
-        self.i2c.write(addr)?;
+            return Err("eeprom failed to ack control byte (write)");
+        }
+        if !self.i2c.write(addr)? {
+            return Err("eeprom failed to ack read address");
+        }
 
         self.i2c.restart()?;
-        self.i2c.write((self.address << 1) | 1)?;
+        if !self.i2c.write((self.address << 1) | 1)? {
+            return Err("eeprom failed to ack control byte (read)");
+        }
         let buf_len = buf.len();
         for (i, byte) in buf.iter_mut().enumerate() {
             *byte = self.i2c.read(i < buf_len - 1)?;
@@ -80,10 +86,16 @@ impl<'a> EEPROM<'a> {
         for (i, byte) in buf.iter().enumerate() {
             if (i == 0) || (pb == 0) {
                 self.i2c.start()?;
-                self.i2c.write(self.address << 1)?;
+                if !self.i2c.write(self.address << 1)? {
-                self.i2c.write(addr + (i as u8))?;
+                    return Err("eeprom failed to ack control byte (write)");
+                }
+                if !self.i2c.write(addr + (i as u8))? {
+                    return Err("eeprom failed to ack write address");
+                }
+            }
+            if !self.i2c.write(*byte)? {
+                return Err("eeprom failed to ack written value");
             }
-            self.i2c.write(*byte)?;
             pb += 1;
 
             if (i == buf_len-1) || (pb == self.page_size) {