serial/usb: update struct ring_buf users

Update the interrupt driver UART drivers that use `struct ring_buf`
internally to report the number of bytes that can be pushed in
`uart_fifo_fill` without fragmentation.

Signed-off-by: Jordan Yates <[email protected]>

drivers/serial/serial_test.c

@@ -130,10 +130,10 @@ static void irq_tx_disable(const struct device *dev)
 static int irq_tx_ready(const struct device *dev)
 {
 	struct serial_vnd_data *data = dev->data;
-	bool ready = (ring_buf_space_get(data->written) != 0);
+	int available = ring_buf_space_get(data->written);
 
-	LOG_DBG("tx ready: %d", ready);
-	return ready;
+	LOG_DBG("tx ready: %d", available);
+	return available;
 }
 
 static void irq_callback_set(const struct device *dev, uart_irq_callback_user_data_t cb,

drivers/serial/uart_emul.c

@@ -231,18 +231,18 @@ static int uart_emul_fifo_read(const struct device *dev, uint8_t *rx_data, int s
 
 static int uart_emul_irq_tx_ready(const struct device *dev)
 {
-	bool ready = false;
+	int available = 0;
 	struct uart_emul_data *data = dev->data;
 
 	K_SPINLOCK(&data->tx_lock) {
 		if (!data->tx_irq_en) {
 			K_SPINLOCK_BREAK;
 		}
 
-		ready = ring_buf_space_get(data->tx_rb) > 0;
+		available = ring_buf_space_get(data->tx_rb);
 	}
 
-	return ready;
+	return available;
 }
 
 static int uart_emul_irq_rx_ready(const struct device *dev)

subsys/usb/device/class/cdc_acm.c

@@ -622,7 +622,7 @@ static int cdc_acm_irq_tx_ready(const struct device *dev)
 	struct cdc_acm_dev_data_t * const dev_data = dev->data;
 
 	if (dev_data->tx_irq_ena && dev_data->tx_ready) {
-		return 1;
+		return ring_buf_space_get(dev_data->tx_ringbuf);
 	}
 
 	return 0;

subsys/usb/device_next/class/usbd_cdc_acm.c

@@ -707,9 +707,7 @@ static int cdc_acm_irq_tx_ready(const struct device *dev)
 	struct cdc_acm_uart_data *const data = dev->data;
 
 	if (check_wq_ctx(dev)) {
-		if (ring_buf_space_get(data->tx_fifo.rb)) {
-			return 1;
-		}
+		return ring_buf_space_get(data->tx_fifo.rb);
 	} else {
 		LOG_WRN("Invoked by inappropriate context");
 		__ASSERT_NO_MSG(false);