usb: stm32: add usb_dc_ep_read_wait/conitinue

usb mass example need usb_dc_ep_read_wait/continue API.
test usb mass storage with RAM DISK on stm32f4 series.

Signed-off-by: qianfan Zhao <[email protected]>

Author: qianfan-Zhao

drivers/usb/device/usb_dc_stm32.c

@@ -488,27 +488,48 @@ int usb_dc_ep_write(const u8_t ep, const u8_t *const data,
 	return ret;
 }
 
-int usb_dc_ep_read(const u8_t ep, u8_t *const data, const u32_t max_data_len,
-		   u32_t * const read_bytes)
+int usb_dc_ep_read_wait(u8_t ep, u8_t *data, u32_t max_data_len,
+			u32_t *read_bytes)
 {
 	struct usb_dc_stm32_ep_state *ep_state = usb_dc_stm32_get_ep_state(ep);
 	u32_t read_count = ep_state->read_count;
 
 	SYS_LOG_DBG("ep 0x%02x, %u bytes, %u+%u, %p", ep,
 		    max_data_len, ep_state->read_offset, read_count, data);
 
-	if (!max_data_len) {
-		goto done;
+	if (!EP_IS_OUT(ep)) { /* check if OUT ep */
+		SYS_LOG_ERR("Wrong endpoint direction: 0x%02x", ep);
+		return -EINVAL;
 	}
 
-	read_count = min(read_count, max_data_len);
-
-	/* Read data previously stored in the buffer */
-	if (read_count) {
+	/* When both buffer and max data to read are zero, just ingore reading
+	 * and return available data in buffer. Otherwise, return data
+	 * previously stored in the buffer.
+	 */
+	if (data) {
+		read_count = min(read_count, max_data_len);
 		memcpy(data, usb_dc_stm32_state.ep_buf[EP_IDX(ep)] +
 		       ep_state->read_offset, read_count);
 		ep_state->read_count -= read_count;
 		ep_state->read_offset += read_count;
+	} else if (max_data_len) {
+		SYS_LOG_ERR("Wrong arguments");
+	}
+
+	if (read_bytes) {
+		*read_bytes = read_count;
+	}
+
+	return 0;
+}
+
+int usb_dc_ep_read_continue(u8_t ep)
+{
+	struct usb_dc_stm32_ep_state *ep_state = usb_dc_stm32_get_ep_state(ep);
+
+	if (!EP_IS_OUT(ep)) { /* Check if OUT ep */
+		SYS_LOG_ERR("Not valid endpoint: %02x", ep);
+		return -EINVAL;
 	}
 
 	/* If no more data in the buffer, start a new read transaction.
@@ -519,9 +540,18 @@ int usb_dc_ep_read(const u8_t ep, u8_t *const data, const u32_t max_data_len,
 				     USB_OTG_FS_MAX_PACKET_SIZE);
 	}
 
-done:
-	if (read_bytes) {
-		*read_bytes = read_count;
+	return 0;
+}
+
+int usb_dc_ep_read(const u8_t ep, u8_t *const data, const u32_t max_data_len,
+		   u32_t * const read_bytes)
+{
+	if (usb_dc_ep_read_wait(ep, data, max_data_len, read_bytes) != 0) {
+		return -EINVAL;
+	}
+
+	if (usb_dc_ep_read_continue(ep) != 0) {
+		return -EINVAL;
 	}
 
 	return 0;