diff --git a/src/common/tusb_common.h b/src/common/tusb_common.h
index 34f3bb8f7..58591f0be 100644
--- a/src/common/tusb_common.h
+++ b/src/common/tusb_common.h
@@ -75,19 +75,6 @@
 
 #include "tusb_timeout.h" // TODO remove
 
-//--------------------------------------------------------------------+
-// Internal Helper used by Host and Device Stack
-//--------------------------------------------------------------------+
-
-// Check if endpoint descriptor is valid per USB specs
-bool tu_edpt_validate(tusb_desc_endpoint_t const * desc_ep, tusb_speed_t speed);
-
-// Bind all endpoint of a interface descriptor to class driver
-void tu_edpt_bind_driver(uint8_t ep2drv[][2], tusb_desc_interface_t const* p_desc, uint16_t desc_len, uint8_t driver_id);
-
-// Calculate total length of n interfaces (depending on IAD)
-uint16_t tu_desc_get_interface_total_len(tusb_desc_interface_t const* desc_itf, uint8_t itf_count, uint16_t max_len);
-
 //--------------------------------------------------------------------+
 // Internal Inline Functions
 //--------------------------------------------------------------------+
diff --git a/src/common/tusb_private.h b/src/common/tusb_private.h
new file mode 100644
index 000000000..5315c352f
--- /dev/null
+++ b/src/common/tusb_private.h
@@ -0,0 +1,61 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2022, Ha Thach (tinyusb.org)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * This file is part of the TinyUSB stack.
+ */
+
+
+#ifndef _TUSB_PRIVATE_H_
+#define _TUSB_PRIVATE_H_
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+typedef struct TU_ATTR_PACKED
+{
+  volatile uint8_t busy    : 1;
+  volatile uint8_t stalled : 1;
+  volatile uint8_t claimed : 1;
+}tu_edpt_state_t;
+
+//--------------------------------------------------------------------+
+// Internal Helper used by Host and Device Stack
+//--------------------------------------------------------------------+
+
+// Check if endpoint descriptor is valid per USB specs
+bool tu_edpt_validate(tusb_desc_endpoint_t const * desc_ep, tusb_speed_t speed);
+
+// Bind all endpoint of a interface descriptor to class driver
+void tu_edpt_bind_driver(uint8_t ep2drv[][2], tusb_desc_interface_t const* p_desc, uint16_t desc_len, uint8_t driver_id);
+
+// Calculate total length of n interfaces (depending on IAD)
+uint16_t tu_desc_get_interface_total_len(tusb_desc_interface_t const* desc_itf, uint8_t itf_count, uint16_t max_len);
+
+bool tu_edpt_claim(tu_edpt_state_t* ep_state, osal_mutex_t mutex);
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif /* _TUSB_PRIVATE_H_ */
diff --git a/src/device/usbd.c b/src/device/usbd.c
index fc66f83c6..4b37e8bd9 100644
--- a/src/device/usbd.c
+++ b/src/device/usbd.c
@@ -29,6 +29,8 @@
 #if CFG_TUD_ENABLED
 
 #include "tusb.h"
+#include "common/tusb_private.h"
+
 #include "device/usbd.h"
 #include "device/usbd_pvt.h"
 #include "device/dcd.h"
@@ -70,6 +72,8 @@ typedef struct
   uint8_t itf2drv[16];     // map interface number to driver (0xff is invalid)
   uint8_t ep2drv[CFG_TUD_ENDPPOINT_MAX][2]; // map endpoint to driver ( 0xff is invalid )
 
+  // TODO 4-bit should be sufficient for ep2drv if we want to save half its bytes
+
   struct TU_ATTR_PACKED
   {
     volatile bool busy    : 1;
diff --git a/src/host/usbh.c b/src/host/usbh.c
index 5d167408a..319031f5b 100644
--- a/src/host/usbh.c
+++ b/src/host/usbh.c
@@ -29,6 +29,8 @@
 #if CFG_TUH_ENABLED
 
 #include "tusb.h"
+#include "common/tusb_private.h"
+
 #include "host/usbh.h"
 #include "host/usbh_classdriver.h"
 #include "hub.h"
@@ -104,14 +106,7 @@ typedef struct {
   uint8_t itf2drv[CFG_TUH_INTERFACE_MAX];  // map interface number to driver (0xff is invalid)
   uint8_t ep2drv[CFG_TUH_ENDPOINT_MAX][2]; // map endpoint to driver ( 0xff is invalid )
 
-  struct TU_ATTR_PACKED
-  {
-    volatile bool busy    : 1;
-    volatile bool stalled : 1;
-    volatile bool claimed : 1;
-
-    // TODO merge ep2drv here, 4-bit should be sufficient
-  }ep_status[CFG_TUH_ENDPOINT_MAX][2];
+  tu_edpt_state_t ep_status[CFG_TUH_ENDPOINT_MAX][2];
 } usbh_device_t;
 
 
@@ -1189,25 +1184,19 @@ static bool parse_configuration_descriptor(uint8_t dev_addr, tusb_desc_configura
 // TODO has some duplication code with device, refactor later
 bool usbh_edpt_claim(uint8_t dev_addr, uint8_t ep_addr)
 {
-  uint8_t const epnum = tu_edpt_number(ep_addr);
-  uint8_t const dir   = tu_edpt_dir(ep_addr);
+  // addr0 is always available
+  if (dev_addr == 0) return true;
 
-  usbh_device_t* dev = get_device(dev_addr);
+  usbh_device_t* dev        = get_device(dev_addr);
+  uint8_t const epnum       = tu_edpt_number(ep_addr);
+  uint8_t const dir         = tu_edpt_dir(ep_addr);
+  tu_edpt_state_t* ep_state = &dev->ep_status[epnum][dir];
 
-  // pre-check to help reducing mutex lock
-  TU_VERIFY((dev->ep_status[epnum][dir].busy == 0) && (dev->ep_status[epnum][dir].claimed == 0));
-  lock_device(dev_addr);
-
-  // can only claim the endpoint if it is not busy and not claimed yet.
-  bool const ret = (dev->ep_status[epnum][dir].busy == 0) && (dev->ep_status[epnum][dir].claimed == 0);
-  if (ret)
-  {
-    dev->ep_status[epnum][dir].claimed = 1;
-  }
-
-  unlock_device(dev_addr);
-
-  return ret;
+#if TUSB_OPT_MUTEX
+  return tu_edpt_claim(ep_state, &_usbh_mutex[dev_addr-1]);
+#else
+  return tu_edpt_claim(ep_state, NULL);
+#endif
 }
 
 // TODO has some duplication code with device, refactor later
@@ -1299,6 +1288,4 @@ bool usbh_edpt_busy(uint8_t dev_addr, uint8_t ep_addr)
   return dev->ep_status[epnum][dir].busy;
 }
 
-
-
 #endif
diff --git a/src/tusb.c b/src/tusb.c
index c6c04262c..6ed2a3c05 100644
--- a/src/tusb.c
+++ b/src/tusb.c
@@ -29,6 +29,7 @@
 #if CFG_TUH_ENABLED || CFG_TUD_ENABLED
 
 #include "tusb.h"
+#include "common/tusb_private.h"
 
 // TODO clean up
 #if CFG_TUD_ENABLED
@@ -67,6 +68,30 @@ bool tusb_inited(void)
 // Internal Helper for both Host and Device stack
 //--------------------------------------------------------------------+
 
+bool tu_edpt_claim(tu_edpt_state_t* ep_state, osal_mutex_t mutex)
+{
+  (void) mutex;
+
+#if TUSB_OPT_MUTEX
+  // pre-check to help reducing mutex lock
+  TU_VERIFY((ep_state->busy == 0) && (ep_state->claimed == 0));
+  osal_mutex_lock(mutex, OSAL_TIMEOUT_WAIT_FOREVER);
+#endif
+
+  // can only claim the endpoint if it is not busy and not claimed yet.
+  bool const available = (ep_state->busy == 0) && (ep_state->claimed == 0);
+  if (available)
+  {
+    ep_state->claimed = 1;
+  }
+
+#if TUSB_OPT_MUTEX
+  osal_mutex_unlock(mutex);
+#endif
+
+  return available;
+}
+
 bool tu_edpt_validate(tusb_desc_endpoint_t const * desc_ep, tusb_speed_t speed)
 {
   uint16_t const max_packet_size = tu_edpt_packet_size(desc_ep);
diff --git a/src/tusb.h b/src/tusb.h
index 549f00b43..222855fcb 100644
--- a/src/tusb.h
+++ b/src/tusb.h
@@ -117,8 +117,6 @@
 //--------------------------------------------------------------------+
 // APPLICATION API
 //--------------------------------------------------------------------+
-/** \ingroup group_application_api
- *  @{ */
 
 // Initialize device/host stack
 // Note: when using with RTOS, this should be called after scheduler/kernel is started.
@@ -131,8 +129,6 @@ bool tusb_inited(void);
 // TODO
 // bool tusb_teardown(void);
 
-/** @} */
-
 #ifdef __cplusplus
  }
 #endif