diff --git a/firmware/libcommon/source/ccid.c b/firmware/libcommon/source/ccid.c
index ff068c49..77d41580 100644
--- a/firmware/libcommon/source/ccid.c
+++ b/firmware/libcommon/source/ccid.c
@@ -126,6 +126,7 @@ static void ConfigureCardDetection(void)
  *-----------------------------------------------------------------------------*/
 extern CCIDDriverConfigurationDescriptors configurationDescriptorCCID;
 
+/* Called during USB enumeration after device is enumerated by host */
 void CCID_configure(void)
 {
 	CCIDDriver_Initialize();
@@ -133,6 +134,7 @@ void CCID_configure(void)
 	PIO_ConfigureIt(&pinSmartCard, ISR_PioSmartCard);
 }
 
+/* called when *different* configuration is set by host */
 void CCID_exit(void)
 {
 	PIO_DisableIt(&pinSmartCard);
@@ -140,6 +142,7 @@ void CCID_exit(void)
 	USART_SetReceiverEnabled(usart_info.base, 0);
 }
 
+/* called when *CCID* configuration is set by host */
 void CCID_init(void)
 {
 	uint8_t pAtr[MAX_ATR_SIZE];
@@ -179,6 +182,7 @@ void CCID_init(void)
 	}
 }
 
+/* main (idle/busy) loop of this USB configuration */
 void CCID_run(void)
 {
 
diff --git a/firmware/libcommon/source/sniffer.c b/firmware/libcommon/source/sniffer.c
index 3f16a7e1..67c11a22 100644
--- a/firmware/libcommon/source/sniffer.c
+++ b/firmware/libcommon/source/sniffer.c
@@ -71,11 +71,13 @@ static struct Usart_info usart_info = {
  *          Initialization routine
  *-----------------------------------------------------------------------------*/
 
+/* Called during USB enumeration after device is enumerated by host */
 void Sniffer_configure(void)
 {
 	TRACE_INFO("Sniffer config\n");
 }
 
+/* called when *different* configuration is set by host */
 void Sniffer_exit(void)
 {
 	TRACE_INFO("Sniffer exit\n");
@@ -84,6 +86,7 @@ void Sniffer_exit(void)
 	USART_SetReceiverEnabled(USART_PHONE, 0);
 }
 
+/* called when *CCID* configuration is set by host */
 void Sniffer_init(void)
 {
 	TRACE_INFO("Sniffer Init\n");
@@ -100,6 +103,7 @@ void Sniffer_init(void)
 	NVIC_EnableIRQ(USART1_IRQn);
 }
 
+/* main (idle/busy) loop of this USB configuration */
 void Sniffer_run(void)
 {
 	check_data_from_phone();