stm32fsdev: set dcd_connect API definitions to strong, Modify documentation.

docs/porting.md

@@ -62,7 +62,7 @@ All of the code for the low-level device API is in `src/portable/<vendor>/<chip
 ##### dcd_init
 Initializes the USB peripheral for device mode and enables it.
 
-If the MCU has an internal pull-up, this function should leave it disabled.
+This function should leave an internal D+/D- pull-up in its default power-on state. `dcd_connect` will be called by the USBD core following `dcd_init`.
 
 #### dcd_int_enable / dcd_int_disable
 
@@ -81,7 +81,7 @@ Called to remote wake up host when suspended (e.g hid keyboard)
 
 ##### dcd_connect / dcd_disconnect
 
-Connect or disconnect the data-line pull-up resistor. Define as a weak function if the MCU has an internal pull-up, otherwise do not define.
+Connect or disconnect the data-line pull-up resistor. Define only if MCU has an internal pull-up. (BSP may define for MCU without internal pull-up.)
 
 #### Special events
 You must let TinyUSB know when certain events occur so that it can continue its work. There are a few methods you can call to queue events for TinyUSB to process.

src/device/dcd.h

@@ -107,8 +107,8 @@ void dcd_set_config (uint8_t rhport, uint8_t config_num);
 void dcd_remote_wakeup(uint8_t rhport);
 
 // Connect or disconnect D+/D- line pull-up resistor.
-// Defined as weak in dcd source if MCU has internal pull-up.
-// Can be strongly defined in BSP.
+// Defined in dcd source if MCU has internal pull-up.
+// Otherwise, may be defined in BSP.
 void dcd_connect(uint8_t rhport) TU_ATTR_WEAK;
 void dcd_disconnect(uint8_t rhport) TU_ATTR_WEAK;
 

src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c

@@ -243,17 +243,17 @@ void dcd_init (uint8_t rhport)
   // Data-line pull-up is left disconnected.
 }
 
-// Define only on MCU with internal pull-up so BSP can override (needed on MCU without internal pull-up)
+// Define only on MCU with internal pull-up. BSP can define on MCU without internal PU.
 #if defined(USB_BCDR_DPPU)
 
-TU_ATTR_WEAK
+// Disable internal D+ PU
 void dcd_disconnect(uint8_t rhport)
 {
   (void) rhport;
   USB->BCDR &= ~(USB_BCDR_DPPU);
 }
 
-TU_ATTR_WEAK
+// Enable internal D+ PU
 void dcd_connect(uint8_t rhport)
 {
   (void) rhport;