diff --git a/arch/arm/src/stm32/stm32_otgfshost.c b/arch/arm/src/stm32/stm32_otgfshost.c
index 699c5c958c0..a693a60bf12 100644
--- a/arch/arm/src/stm32/stm32_otgfshost.c
+++ b/arch/arm/src/stm32/stm32_otgfshost.c
@@ -1881,7 +1881,13 @@ static ssize_t stm32_in_transfer(FAR struct stm32_usbhost_s *priv, int chidx,
 
               if (xfrd > 0)
                 {
-                  /* Yes, return the amount of data received */
+                  /* Yes, return the amount of data received.
+                   *
+                   * REVISIT: This behavior is clearly correct for CDC/ACM
+                   * bulk transfers and HID interrupt transfers.  But I am
+                   * not so certain for MSC bulk transfers which, I think,
+                   * could have NAKed packets in the middle of a transfer.
+                   */
 
                   return xfrd;
                 }
diff --git a/arch/arm/src/stm32/stm32_otghshost.c b/arch/arm/src/stm32/stm32_otghshost.c
index 2a100e7a54e..d78ab4a3cb9 100644
--- a/arch/arm/src/stm32/stm32_otghshost.c
+++ b/arch/arm/src/stm32/stm32_otghshost.c
@@ -1886,7 +1886,13 @@ static ssize_t stm32_in_transfer(FAR struct stm32_usbhost_s *priv, int chidx,
 
               if (xfrd > 0)
                 {
-                  /* Yes, return the amount of data received */
+                  /* Yes, return the amount of data received.
+                   *
+                   * REVISIT: This behavior is clearly correct for CDC/ACM
+                   * bulk transfers and HID interrupt transfers.  But I am
+                   * not so certain for MSC bulk transfers which, I think,
+                   * could have NAKed packets in the middle of a transfer.
+                   */
 
                   return xfrd;
                 }
diff --git a/arch/arm/src/stm32f7/stm32_otghost.c b/arch/arm/src/stm32f7/stm32_otghost.c
index 03a9ca1a1ca..da25d3dbc9b 100644
--- a/arch/arm/src/stm32f7/stm32_otghost.c
+++ b/arch/arm/src/stm32f7/stm32_otghost.c
@@ -1880,7 +1880,13 @@ static ssize_t stm32_in_transfer(FAR struct stm32_usbhost_s *priv, int chidx,
 
               if (xfrd > 0)
                 {
-                  /* Yes, return the amount of data received */
+                  /* Yes, return the amount of data received.
+                   *
+                   * REVISIT: This behavior is clearly correct for CDC/ACM
+                   * bulk transfers and HID interrupt transfers.  But I am
+                   * not so certain for MSC bulk transfers which, I think,
+                   * could have NAKed packets in the middle of a transfer.
+                   */
 
                   return xfrd;
                 }
diff --git a/arch/arm/src/stm32l4/stm32l4_otgfshost.c b/arch/arm/src/stm32l4/stm32l4_otgfshost.c
index 7855ea2eebd..b0fa7645eab 100644
--- a/arch/arm/src/stm32l4/stm32l4_otgfshost.c
+++ b/arch/arm/src/stm32l4/stm32l4_otgfshost.c
@@ -1885,7 +1885,13 @@ static ssize_t stm32l4_in_transfer(FAR struct stm32l4_usbhost_s *priv,
 
               if (xfrd > 0)
                 {
-                  /* Yes, return the amount of data received */
+                  /* Yes, return the amount of data received.
+                   *
+                   * REVISIT: This behavior is clearly correct for CDC/ACM
+                   * bulk transfers and HID interrupt transfers.  But I am
+                   * not so certain for MSC bulk transfers which, I think,
+                   * could have NAKed packets in the middle of a transfer.
+                   */
 
                   return xfrd;
                 }