drivers: entropy: Use likely()/unlikely() macros to speed up the API

This commit introduces usage of likely()/unlikely() macros in order
to speed up the entropy_get_entropy_isr() API.

Signed-off-by: Piotr Zięcik <[email protected]>

Author: pizi-nordic

drivers/entropy/entropy_nrf5.c

@@ -256,7 +256,7 @@ static int entropy_nrf5_get_entropy_isr(struct device *dev, u8_t *buf, u16_t len
 	/* Check if this API is called on correct driver instance. */
 	__ASSERT_NO_MSG(&entropy_nrf5_data == DEV_DATA(dev));
 
-	if (!(flags & ENTROPY_BUSYWAIT)) {
+	if (likely((flags & ENTROPY_BUSYWAIT) == 0)) {
 		return rng_pool_get((struct rng_pool *)(entropy_nrf5_data.isr),
 				    buf, len);
 	}

include/entropy.h

@@ -96,9 +96,10 @@ static inline int entropy_get_entropy_isr(struct device *dev,
 {
 	const struct entropy_driver_api *api = dev->driver_api;
 
-	if (!api->get_entropy_isr) {
+	if (unlikely(!api->get_entropy_isr)) {
 		return -ENOTSUP;
 	}
+
 	return api->get_entropy_isr(dev, buffer, length, flags);
 }