mfd: wm831x: Feed the device UUID into device_add_randomness()

wm831x devices contain a unique ID value. Feed this into the newly added
device_add_randomness() to add some per device seed data to the pool.

Signed-off-by: Mark Brown <[e-mail]>
Signed-off-by: Theodore Ts'o <[e-mail]>
Cc: [e-mail]

drivers/mfd/wm831x-otp.c

···
 #include <linux/bcd.h>
 #include <linux/delay.h>
 #include <linux/mfd/core.h>
+#include <linux/random.h>
 
 #include <linux/mfd/wm831x/core.h>
 #include <linux/mfd/wm831x/otp.h>
···
 
 int wm831x_otp_init(struct wm831x *wm831x)
 {
+	char uuid[WM831X_UNIQUE_ID_LEN];
 	int ret;
 
 	ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
 	if (ret != 0)
 		dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
 			ret);
+
+	ret = wm831x_unique_id_read(wm831x, uuid);
+	if (ret == 0)
+		add_device_randomness(uuid, sizeof(uuid));
+	else
+		dev_err(wm831x->dev, "Failed to read UUID: %d\n", ret);
 
 	return ret;
 }