USB host: Modify the transfer() and asynch() methods so that the actual size of the transfer is returned. Unverified on initial commit.

ChangeLog

@@ -10306,3 +10306,7 @@
 	  (2015-05-03).
 	* fs/vfs/fs_poll.c: Fix resource leak and memory corruption on poll
 	  failure.  From Jussi Kivilinna (2015-05-04).
+	* All USB host drivers in arch/ and all USB class drivers in drivers/usbhost:
+	  Modify the transfer() and asynch() methods so that the actual size of
+	  the transfer is returned.  Unverified on initial commit (2015-05-05).
+

arch/arm/src/lpc17xx/Kconfig

@@ -961,16 +961,14 @@ config USBHOST_IOBUFSIZE
 		Size of one end-user I/O buffer.  This can be zero if the application
 		can guarantee that all end-user I/O buffers reside in AHB SRAM.
 
-config LPC17_USBHOST_NASYNCH
+config LPC17_USBHOST_NPREALLOC
-	int "Number asynch transfers"
+	int "Max concurrent transfers"
 	default 8 if USBHOST_HUB
 	default 4 if !USBHOST_HUB
-	depends on USBHOST_ASYNCH
 	---help---
 		This number represents a number of pre-allocated structures to support
-		asynchronous IN data transfers.  This number effective determines that
+		concurrent data transfers.  This number limits that number of concurrent
-		number of concurrent asynchronous IN endpoint transfer that can be
+		asynchronous IN endpoint transfer that can be supported.
-		supported.
 
 config USBHOST_BULK_DISABLE
 	bool "Disable bulk EPs"

arch/arm/src/lpc31xx/lpc31_ehci.c

@@ -545,7 +545,7 @@ static int lpc31_ctrlin(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
          FAR const struct usb_ctrlreq_s *req, FAR uint8_t *buffer);
 static int lpc31_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
          FAR const struct usb_ctrlreq_s *req, FAR const uint8_t *buffer);
-static int lpc31_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t lpc31_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
          FAR uint8_t *buffer, size_t buflen);
 #ifdef CONFIG_USBHOST_ASYNCH
 static int lpc31_asynch(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
@@ -2630,6 +2630,7 @@ static inline int lpc31_asynch_setup(struct lpc31_rhport_s *rhport,
 static void lpc31_asynch_completion(struct lpc31_epinfo_s *epinfo)
 {
   usbhost_asynch_t callback;
+  ssize_t nbytes;
   void *arg;
   int result;
 
@@ -2641,15 +2642,23 @@ static void lpc31_asynch_completion(struct lpc31_epinfo_s *epinfo)
   callback         = epinfo->callback;
   arg              = epinfo->arg;
   result           = epinfo->result;
+  nbytes           = epinfo->xfrd;
 
   epinfo->callback = NULL;
   epinfo->arg      = NULL;
   epinfo->result   = OK;
   epinfo->iocwait  = false;
 
-  /* Then perform the callback */
+  /* Then perform the callback.  Provide the number of bytes successfully
+   * transferred or the negated errno value in the event of a failure.
+   */
 
-  callback(arg, result);
+  if (result < 0)
+    {
+      nbytes = (ssize_t)result;
+    }
+
+  callback(arg, nbytes);
 }
 #endif
 
@@ -4273,8 +4282,9 @@ static int lpc31_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
  *   buflen - The length of the data to be sent or received.
  *
  * Returned Values:
- *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   On success, a non-negative value is returned that indicates the number
- *   returned indicating the nature of the failure:
+ *   of bytes successfully transferred.  On a failure, a negated errno value is
+ *   returned that indicates the nature of the failure:
  *
  *     EAGAIN - If devices NAKs the transfer (or NYET or other error where
  *              it may be appropriate to restart the entire transaction).
@@ -4288,8 +4298,8 @@ static int lpc31_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
  *
  *******************************************************************************/
 
-static int lpc31_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t lpc31_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
-                        FAR uint8_t *buffer, size_t buflen)
+                              FAR uint8_t *buffer, size_t buflen)
 {
   struct lpc31_rhport_s *rhport = (struct lpc31_rhport_s *)drvr;
   struct lpc31_epinfo_s *epinfo = (struct lpc31_epinfo_s *)ep;
@@ -4347,13 +4357,13 @@ static int lpc31_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
 
   nbytes = lpc31_transfer_wait(epinfo);
   lpc31_givesem(&g_ehci.exclsem);
-  return nbytes >= 0 ? OK : (int)nbytes;
+  return nbytes;
 
 errout_with_iocwait:
   epinfo->iocwait = false;
 errout_with_sem:
   lpc31_givesem(&g_ehci.exclsem);
-  return ret;
+  return (ssize_t)ret;
 }
 
 /*******************************************************************************
@@ -4676,12 +4686,7 @@ static int lpc31_connect(FAR struct usbhost_driver_s *drvr,
 static void lpc31_disconnect(FAR struct usbhost_driver_s *drvr,
                              FAR struct usbhost_hubport_s *hport)
 {
-  struct lpc31_rhport_s *rhport = (struct lpc31_rhport_s *)drvr;
+  DEBUGASSERT(hport != NULL);
-  DEBUGASSERT(rhport != NULL && hport != NULL);
-
-  /* Unbind the class */
-  /* REVISIT:  Is there more that needs to be done? */
-
   hport->devclass = NULL;
 }
 

arch/arm/src/sama5/sam_ehci.c

@@ -421,7 +421,7 @@ static int sam_ctrlin(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
          FAR const struct usb_ctrlreq_s *req, FAR uint8_t *buffer);
 static int sam_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
          FAR const struct usb_ctrlreq_s *req, FAR const uint8_t *buffer);
-static int sam_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t sam_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
          FAR uint8_t *buffer, size_t buflen);
 #ifdef CONFIG_USBHOST_ASYNCH
 static int sam_asynch(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
@@ -2448,6 +2448,7 @@ static inline int sam_asynch_setup(struct sam_rhport_s *rhport,
 static void sam_asynch_completion(struct sam_epinfo_s *epinfo)
 {
   usbhost_asynch_t callback;
+  ssize_t nbytes;
   void *arg;
   int result;
 
@@ -2459,15 +2460,23 @@ static void sam_asynch_completion(struct sam_epinfo_s *epinfo)
   callback         = epinfo->callback;
   arg              = epinfo->arg;
   result           = epinfo->result;
+  nbytes           = epinfo->xfrd;
 
   epinfo->callback = NULL;
   epinfo->arg      = NULL;
   epinfo->result   = OK;
   epinfo->iocwait  = false;
 
-  /* Then perform the callback */
+  /* Then perform the callback.  Provide the number of bytes successfully
+   * transferred or the negated errno value in the event of a failure.
+   */
 
-  callback(arg, result);
+  if (result < 0)
+    {
+      nbytes = (ssize_t)result;
+    }
+
+  callback(arg, nbytes);
 }
 #endif
 
@@ -4099,8 +4108,9 @@ static int sam_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
  *   buflen - The length of the data to be sent or received.
  *
  * Returned Values:
- *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   On success, a non-negative value is returned that indicates the number
- *   returned indicating the nature of the failure:
+ *   of bytes successfully transferred.  On a failure, a negated errno value is
+ *   returned that indicates the nature of the failure:
  *
  *     EAGAIN - If devices NAKs the transfer (or NYET or other error where
  *              it may be appropriate to restart the entire transaction).
@@ -4114,8 +4124,8 @@ static int sam_ctrlout(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
  *
  *******************************************************************************/
 
-static int sam_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t sam_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
-                        FAR uint8_t *buffer, size_t buflen)
+                            FAR uint8_t *buffer, size_t buflen)
 {
   struct sam_rhport_s *rhport = (struct sam_rhport_s *)drvr;
   struct sam_epinfo_s *epinfo = (struct sam_epinfo_s *)ep;
@@ -4174,13 +4184,13 @@ static int sam_transfer(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
 
   nbytes = sam_transfer_wait(epinfo);
   sam_givesem(&g_ehci.exclsem);
-  return nbytes >= 0 ? OK : (int)nbytes;
+  return nbytes;
 
 errout_with_iocwait:
   epinfo->iocwait = false;
 errout_with_sem:
   sam_givesem(&g_ehci.exclsem);
-  return ret;
+  return (ssize_t)ret;
 }
 
 /*******************************************************************************
@@ -4503,13 +4513,8 @@ static int sam_connect(FAR struct usbhost_driver_s *drvr,
 static void sam_disconnect(FAR struct usbhost_driver_s *drvr,
                            FAR struct usbhost_hubport_s *hport)
 {
-  struct sam_rhport_s *rhport = (struct sam_rhport_s *)drvr;
+  DEBUGASSERT(hport != NULL);
-  DEBUGASSERT(rhport != NULL && hport != NULL);
+  hport->devclass = NULL;
-
-  /* Unbind the class */
-  /* REVISIT:  Is there more that needs to be done? */
-
-  rhport->hport.hport.devclass = NULL;
 }
 
 /*******************************************************************************

arch/arm/src/sama5/sam_ohci.c

@@ -219,14 +219,15 @@
 
 struct sam_eplist_s
 {
-  volatile bool    wdhwait;    /* TRUE: Thread is waiting for WDH interrupt */
+  volatile bool     wdhwait;   /* TRUE: Thread is waiting for WDH interrupt */
-  sem_t            wdhsem;     /* Semaphore used to wait for Writeback Done Head event */
+  sem_t             wdhsem;    /* Semaphore used to wait for Writeback Done Head event */
 #ifdef CONFIG_USBHOST_ASYNCH
-  usbhost_asynch_t callback;   /* Transfer complete callback */
+  usbhost_asynch_t  callback;  /* Transfer complete callback */
-  void            *arg;        /* Argument that accompanies the callback */
+  void             *arg;       /* Argument that accompanies the callback */
-  uint8_t         *buffer;     /* Buffer being transferred */
+  uint16_t          buflen;    /* Length of the buffer */
-  uint16_t         buflen;     /* Length of the buffer */
 #endif
+  uint8_t          *buffer;    /* Buffer being transferred */
+  uint16_t          xfrd;      /* Number of bytes completed in the last transfer */
   struct sam_ed_s  *ed;        /* Endpoint descriptor (ED) */
   struct sam_gtd_s *tail;      /* Tail transfer descriptor (TD) */
 };
@@ -444,8 +445,8 @@ static int sam_ctrlout(struct usbhost_driver_s *drvr, usbhost_ep_t ep0,
 static int sam_transfer_common(struct sam_rhport_s *rhport,
                                struct sam_eplist_s *eplist,
                                uint8_t *buffer, size_t buflen);
-static int sam_transfer(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t sam_transfer(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
-                        uint8_t *buffer, size_t buflen);
+                            uint8_t *buffer, size_t buflen);
 #ifdef CONFIG_USBHOST_ASYNCH
 static void sam_asynch_completion(struct sam_eplist_s *eplist);
 static int sam_asynch(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
@@ -2077,6 +2078,8 @@ static void sam_wdh_bottomhalf(void)
   struct sam_gtd_s *td;
   struct sam_gtd_s *next;
   struct sam_ed_s *ed;
+  uintptr_t paddr;
+  uintptr_t tmp;
 
   /* The host controller just wrote the one finished TDs into the HCCA
    * done head.  This may include multiple packets that were transferred
@@ -2147,6 +2150,16 @@ static void sam_wdh_bottomhalf(void)
         }
 #endif
 
+      /* Determine the size of the transfer by subtracting the current buffer
+       * pointer (CBP) from the initial buffer pointer (on packet receipt only).
+       */
+
+      paddr = sam_physramaddr((uintptr_t)eplist->buffer);
+      tmp   = (uintptr_t)td->hw.cbp - paddr;
+      DEBUGASSERT(tmp < UINT16_MAX);
+
+      eplist->xfrd = (uint16_t)tmp;
+
       /* Return the TD to the free list */
 
       next = (struct sam_gtd_s *)sam_virtramaddr(td->hw.nexttd);
@@ -3253,12 +3266,13 @@ static int sam_transfer_common(struct sam_rhport_s *rhport,
  *
  *******************************************************************************/
 
-static int sam_transfer(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+static ssize_t sam_transfer(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
-                        uint8_t *buffer, size_t buflen)
+                            uint8_t *buffer, size_t buflen)
 {
   struct sam_rhport_s *rhport = (struct sam_rhport_s *)drvr;
   struct sam_eplist_s *eplist = (struct sam_eplist_s *)ep;
   struct sam_ed_s *ed;
+  ssize_t nbytes;
   bool in;
   int ret;
 
@@ -3339,21 +3353,24 @@ static int sam_transfer(struct usbhost_driver_s *drvr, usbhost_ep_t ep,
                                  (uintptr_t)buffer + buflen);
         }
 
-      ret = OK;
+      nbytes = eplist->xfrd;
-    }
+      DEBUGASSERT(nbytes >=0 && nbytes <= buflen);
-  else
+
-    {
+      sam_givesem(&g_ohci.exclsem);
-      usbhost_trace2(OHCI_TRACE2_BADTDSTATUS, RHPORT(rhport),
+      return nbytes;
-                     ed->tdstatus);
-      ret = ed->tdstatus == TD_CC_STALL ? -EPERM : -EIO;
     }
 
+  /* A transfer error occurred */
+
+  usbhost_trace2(OHCI_TRACE2_BADTDSTATUS, RHPORT(rhport), ed->tdstatus);
+  ret = ed->tdstatus == TD_CC_STALL ? -EPERM : -EIO;
+
 errout:
   /* Make sure that there is no outstanding request on this endpoint */
 
   eplist->wdhwait = false;
   sam_givesem(&g_ohci.exclsem);
-  return ret;
+  return (ssize_t)ret;
 }
 
 /*******************************************************************************
@@ -3382,7 +3399,7 @@ static void sam_asynch_completion(struct sam_eplist_s *eplist)
   struct sam_ed_s *ed;
   usbhost_asynch_t callback;
   void *arg;
-  int result;
+  ssize_t nbytes;
 
   DEBUGASSERT(eplist->ed && eplist->tail && eplist->callback != NULL && 
               eplist->buffer != NULL && eplist->buflen > 0);
@@ -3407,12 +3424,13 @@ static void sam_asynch_completion(struct sam_eplist_s *eplist)
           arch_invalidate_dcache(buffaddr, buffaddr + eplist->buflen);
         }
 
-      result = OK;
+      nbytes = eplist->xfrd;
+      DEBUGASSERT(nbytes >= 0 && nbytes <= eplist->buflen);
     }
   else
     {
       usbhost_trace1(OHCI_TRACE1_BADTDSTATUS, ed->tdstatus);
-      result = ed->tdstatus == TD_CC_STALL ? -EPERM : -EIO;
+      nbytes = (ed->tdstatus == TD_CC_STALL) ? -EPERM : -EIO;
     }
 
   /* Extract the callback information before freeing the buffer */
@@ -3430,7 +3448,7 @@ static void sam_asynch_completion(struct sam_eplist_s *eplist)
 
   /* Then perform the callback */
 
-  callback(arg, result);
+  callback(arg, nbytes);
 }
 #endif
 

drivers/usbhost/usbhost_hidmouse.c

@@ -1052,6 +1052,7 @@ static int usbhost_mouse_poll(int argc, char *argv[])
   unsigned int npolls = 0;
 #endif
   unsigned int nerrors = 0;
+  ssize_t nbytes;
   int ret;
 
   uvdbg("Started\n");
@@ -1084,14 +1085,14 @@ static int usbhost_mouse_poll(int argc, char *argv[])
        * sends data.
        */
 
-      ret = DRVR_TRANSFER(hport->drvr, priv->epin,
+      nbytes = DRVR_TRANSFER(hport->drvr, priv->epin,
-                          priv->tbuffer, priv->tbuflen);
+                             priv->tbuffer, priv->tbuflen);
 
       /* Check for errors -- Bail if an excessive number of consecutive
        * errors are encountered.
        */
 
-      if (ret < 0)
+      if (nbytes < 0)
         {
           /* If DRVR_TRANSFER() returns EAGAIN, that simply means that
            * the devices was not ready and has NAK'ed the transfer.  That
@@ -1100,11 +1101,12 @@ static int usbhost_mouse_poll(int argc, char *argv[])
            */
 
           udbg("ERROR: DRVR_TRANSFER returned: %d/%d\n", ret, nerrors);
-          if (ret != -EAGAIN)
+          if (nbytes != -EAGAIN)
             {
               if (++nerrors > 200)
                 {
                   udbg("Too many errors... aborting: %d\n", nerrors);
+                  ret = (int)nbytes;
                   break;
                 }
             }

drivers/usbhost/usbhost_hub.c

@@ -86,7 +86,7 @@
 #  error Asynchronous transfer support is required (CONFIG_USBHOST_ASYNCH)
 #endif
 
-#ifdef CONFIG_USBHOST_HUB_POLLMSEC
+#ifndef CONFIG_USBHOST_HUB_POLLMSEC
 #  define CONFIG_USBHOST_HUB_POLLMSEC 400
 #endif
 
@@ -166,7 +166,7 @@ static void usbhost_disconnect_event(FAR void *arg);
 
 static inline uint16_t usbhost_getle16(const uint8_t *val);
 static void usbhost_putle16(uint8_t *dest, uint16_t val);
-static void usbhost_callback(FAR void *arg, int result);
+static void usbhost_callback(FAR void *arg, ssize_t nbytes);
 
 /* struct usbhost_registry_s methods */
 
@@ -1149,7 +1149,8 @@ static void usbhost_putle16(uint8_t *dest, uint16_t val)
  *
  * Input Parameters:
  *   arg - The argument provided with the asynchronous I/O was setup
- *   result - The result of the transfer
+ *   nbytes - The number of bytes actually transferred (or a negated errno
+ *     value;
  *
  * Returned Values:
  *   None
@@ -1159,7 +1160,7 @@ static void usbhost_putle16(uint8_t *dest, uint16_t val)
  *
  ****************************************************************************/
 
-static void usbhost_callback(FAR void *arg, int result)
+static void usbhost_callback(FAR void *arg, ssize_t nbytes)
 {
   FAR struct usbhost_class_s *hubclass;
   FAR struct usbhost_hubpriv_s *priv;
@@ -1173,22 +1174,22 @@ static void usbhost_callback(FAR void *arg, int result)
    * transfer will pend until data is available (OHCI and EHCI).  On lower
    * end host controllers (like STM32 and EFM32), the transfer will fail
    * immediately when the device NAKs the first attempted interrupt IN
-   * transfer (with result == EAGAIN).  In that case (or in the case of
+   * transfer (with nbytes == -EAGAIN).  In that case (or in the case of
    * other errors), we must fall back to polling.
    */
 
-  if (result != OK)
+  if (nbytes < 0)
     {
       /* This debug output is good to know, but really a nuisance for
        * those configurations where we have to fall back to polling.
-       * FIX:  Don't output the message is the result is EAGAIN.
+       * FIX:  Don't output the message is the result is -EAGAIN.
        */
 
 #if defined(CONFIG_DEBUG_USB) && !defined(CONFIG_DEBUG_VERBOSE)
-      if (result != EAGAIN)
+      if (nbytes != -EAGAIN)
 #endif
         {
-          ulldbg("ERROR: Transfer failed: %d\n", result);
+          ulldbg("ERROR: Transfer failed: %d\n", (int)nbytes);
         }
 
       /* Indicate there there is nothing to do.  So when the work is

drivers/usbhost/usbhost_storage.c

@@ -711,7 +711,7 @@ static inline int usbhost_testunitready(FAR struct usbhost_state_s *priv)
 {
   FAR struct usbhost_hubport_s *hport;
   FAR struct usbmsc_cbw_s *cbw;
-  int result;
+  ssize_t nbytes;
 
   DEBUGASSERT(priv->usbclass.hport);
   hport = priv->usbclass.hport;
@@ -728,28 +728,28 @@ static inline int usbhost_testunitready(FAR struct usbhost_state_s *priv)
   /* Construct and send the CBW */
 
   usbhost_testunitreadycbw(cbw);
-  result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                         (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-  if (result == OK)
+  if (nbytes >= 0)
     {
       /* Receive the CSW */
 
-      result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+      nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                              priv->tbuffer, USBMSC_CSW_SIZEOF);
-      if (result == OK)
+      if (nbytes >= 0)
         {
           usbhost_dumpcsw((FAR struct usbmsc_csw_s *)priv->tbuffer);
         }
     }
 
-  return result;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 
 static inline int usbhost_requestsense(FAR struct usbhost_state_s *priv)
 {
   FAR struct usbhost_hubport_s *hport;
   FAR struct usbmsc_cbw_s *cbw;
-  int result;
+  ssize_t nbytes;
 
   DEBUGASSERT(priv->usbclass.hport);
   hport = priv->usbclass.hport;
@@ -766,28 +766,28 @@ static inline int usbhost_requestsense(FAR struct usbhost_state_s *priv)
   /* Construct and send the CBW */
 
   usbhost_requestsensecbw(cbw);
-  result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                         (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-  if (result == OK)
+  if (nbytes >= 0)
     {
       /* Receive the sense data response */
 
-      result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+      nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                              priv->tbuffer, SCSIRESP_FIXEDSENSEDATA_SIZEOF);
-      if (result == OK)
+      if (nbytes >= 0)
         {
           /* Receive the CSW */
 
-          result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+          nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                  priv->tbuffer, USBMSC_CSW_SIZEOF);
-          if (result == OK)
+          if (nbytes >= 0)
             {
               usbhost_dumpcsw((FAR struct usbmsc_csw_s *)priv->tbuffer);
             }
         }
     }
 
-  return result;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 
 static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv)
@@ -795,7 +795,7 @@ static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv)
   FAR struct usbhost_hubport_s *hport;
   FAR struct usbmsc_cbw_s *cbw;
   FAR struct scsiresp_readcapacity10_s *resp;
-  int result;
+  ssize_t nbytes;
 
   DEBUGASSERT(priv->usbclass.hport);
   hport = priv->usbclass.hport;
@@ -812,15 +812,15 @@ static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv)
   /* Construct and send the CBW */
 
   usbhost_readcapacitycbw(cbw);
-  result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                         (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-  if (result == OK)
+  if (nbytes >= 0)
     {
       /* Receive the read capacity CBW IN response */
 
-      result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+      nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                              priv->tbuffer, SCSIRESP_READCAPACITY10_SIZEOF);
-      if (result == OK)
+      if (nbytes >= 0)
         {
           /* Save the capacity information */
 
@@ -830,23 +830,23 @@ static inline int usbhost_readcapacity(FAR struct usbhost_state_s *priv)
 
           /* Receive the CSW */
 
-          result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+          nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                  priv->tbuffer, USBMSC_CSW_SIZEOF);
-          if (result == OK)
+          if (nbytes >= 0)
             {
               usbhost_dumpcsw((FAR struct usbmsc_csw_s *)priv->tbuffer);
             }
         }
     }
 
-  return result;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 
 static inline int usbhost_inquiry(FAR struct usbhost_state_s *priv)
 {
   FAR struct usbhost_hubport_s *hport;
   FAR struct usbmsc_cbw_s *cbw;
-  int result;
+  ssize_t nbytes;
 
   DEBUGASSERT(priv->usbclass.hport);
   hport = priv->usbclass.hport;
@@ -863,35 +863,35 @@ static inline int usbhost_inquiry(FAR struct usbhost_state_s *priv)
   /* Construct and send the CBW */
 
   usbhost_inquirycbw(cbw);
-  result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                          (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-  if (result == OK)
+  if (nbytes >= 0)
     {
       /* Receive the CBW IN response */
 
-      result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+      nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                              priv->tbuffer, SCSIRESP_INQUIRY_SIZEOF);
-      if (result == OK)
+      if (nbytes >= 0)
         {
 #if 0
           FAR struct scsiresp_inquiry_s *resp;
 
           /* TODO: If USB debug is enabled, dump the response data here */
+
           resp = (FAR struct scsiresp_inquiry_s *)priv->tbuffer;
 #endif
-
           /* Receive the CSW */
 
-          result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+          nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                  priv->tbuffer, USBMSC_CSW_SIZEOF);
-          if (result == OK)
+          if (nbytes >= 0)
             {
               usbhost_dumpcsw((FAR struct usbmsc_csw_s *)priv->tbuffer);
             }
         }
     }
 
-  return result;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 
 /****************************************************************************
@@ -1977,8 +1977,7 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
 {
   FAR struct usbhost_state_s *priv;
   FAR struct usbhost_hubport_s *hport;
-  ssize_t ret = 0;
+  ssize_t nbytes = 0;
-  int result;
 
   DEBUGASSERT(inode && inode->i_private);
   priv = (FAR struct usbhost_state_s *)inode->i_private;
@@ -1998,7 +1997,7 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
        * attempt to read from the device.
        */
 
-      ret = -ENODEV;
+      nbytes = -ENODEV;
     }
   else if (nsectors > 0)
     {
@@ -2008,7 +2007,7 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
 
       /* Assume allocation failure */
 
-      ret = -ENOMEM;
+      nbytes = -ENOMEM;
 
       /* Initialize a CBW (re-using the allocated transfer buffer) */
 
@@ -2023,26 +2022,26 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
             {
               /* Assume some device failure */
 
-              ret = -ENODEV;
+              nbytes = -ENODEV;
 
               /* Construct and send the CBW */
 
               usbhost_readcbw(startsector, priv->blocksize, nsectors, cbw);
-              result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+              nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                                      (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-              if (result == OK)
+              if (nbytes >= 0)
                 {
                   /* Receive the user data */
 
-                  result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+                  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                          buffer, priv->blocksize * nsectors);
-                  if (result == OK)
+                  if (nbytes >= 0)
                     {
                       /* Receive the CSW */
 
-                      result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+                      nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                              priv->tbuffer, USBMSC_CSW_SIZEOF);
-                      if (result == OK)
+                      if (nbytes >= 0)
                         {
                           FAR struct usbmsc_csw_s *csw;
 
@@ -2051,12 +2050,12 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
                           csw = (FAR struct usbmsc_csw_s *)priv->tbuffer;
                           if (csw->status == 0)
                             {
-                              ret = nsectors;
+                              nbytes = nsectors;
                             }
                         }
                     }
                 }
-            } while (result == -EAGAIN);
+            } while (nbytes == -EAGAIN);
         }
 
       usbhost_givesem(&priv->exclsem);
@@ -2064,7 +2063,7 @@ static ssize_t usbhost_read(FAR struct inode *inode, unsigned char *buffer,
 
   /* On success, return the number of blocks read */
 
-  return ret;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 
 /****************************************************************************
@@ -2082,8 +2081,7 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
 {
   FAR struct usbhost_state_s *priv;
   FAR struct usbhost_hubport_s *hport;
-  ssize_t ret;
+  ssize_t nbytes;
-  int result;
 
   uvdbg("sector: %d nsectors: %d sectorsize: %d\n");
 
@@ -2102,7 +2100,7 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
        * attempt to write to the device.
        */
 
-      ret = -ENODEV;
+      nbytes = -ENODEV;
     }
   else
     {
@@ -2112,7 +2110,7 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
 
      /* Assume allocation failure */
 
-      ret = -ENOMEM;
+      nbytes = -ENOMEM;
 
       /* Initialize a CBW (re-using the allocated transfer buffer) */
 
@@ -2121,26 +2119,26 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
         {
           /* Assume some device failure */
 
-          ret = -ENODEV;
+          nbytes = -ENODEV;
 
           /* Construct and send the CBW */
 
           usbhost_writecbw(startsector, priv->blocksize, nsectors, cbw);
-          result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+          nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                                  (uint8_t*)cbw, USBMSC_CBW_SIZEOF);
-          if (result == OK)
+          if (nbytes >= 0)
             {
               /* Send the user data */
 
-              result = DRVR_TRANSFER(hport->drvr, priv->bulkout,
+              nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkout,
                                      (uint8_t*)buffer, priv->blocksize * nsectors);
-              if (result == OK)
+              if (nbytes >= 0)
                 {
                   /* Receive the CSW */
 
-                  result = DRVR_TRANSFER(hport->drvr, priv->bulkin,
+                  nbytes = DRVR_TRANSFER(hport->drvr, priv->bulkin,
                                          priv->tbuffer, USBMSC_CSW_SIZEOF);
-                  if (result == OK)
+                  if (nbytes >= 0)
                     {
                       FAR struct usbmsc_csw_s *csw;
 
@@ -2149,7 +2147,7 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
                       csw = (FAR struct usbmsc_csw_s *)priv->tbuffer;
                       if (csw->status == 0)
                         {
-                          ret = nsectors;
+                          nbytes = nsectors;
                         }
                     }
                 }
@@ -2161,7 +2159,7 @@ static ssize_t usbhost_write(FAR struct inode *inode, const unsigned char *buffe
 
   /* On success, return the number of blocks written */
 
-  return ret;
+  return nbytes < 0 ? (int)nbytes : OK;
 }
 #endif
 

include/nuttx/usb/usbhost.h

@@ -490,8 +490,9 @@
  *   buflen - The length of the data to be sent or received.
  *
  * Returned Values:
- *   On success, zero (OK) is returned. On a failure, a negated errno value is
+ *   On success, a non-negative value is returned that indicates the number
- *   returned indicating the nature of the failure:
+ *   of bytes successfully transferred.  On a failure, a negated errno value is
+ *   returned that indicates the nature of the failure:
  *
  *     EAGAIN - If devices NAKs the transfer (or NYET or other error where
  *              it may be appropriate to restart the entire transaction).
@@ -791,9 +792,13 @@ struct usbhost_connection_s
                    FAR struct usbhost_hubport_s *hport);
 };
 
-/* Callback type used with asynchronous transfers */
+/* Callback type used with asynchronous transfers.  The result of the
+ * transfer is provided by the 'result' parameters.  If >= 0, then 'result'
+ * is the number of bytes transfers. If < 0 then the transfer failed and
+ * result is a negated errno value that indicates the nature of the failure.
+ */
 
-typedef CODE void (*usbhost_asynch_t)(FAR void *arg, int result);
+typedef CODE void (*usbhost_asynch_t)(FAR void *arg, ssize_t result);
 
 /* struct usbhost_driver_s provides access to the USB host driver from the
  * USB host class implementation.
@@ -869,8 +874,8 @@ struct usbhost_driver_s
    * transfer has completed.
    */
 
-  int (*transfer)(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
+  ssize_t (*transfer)(FAR struct usbhost_driver_s *drvr, usbhost_ep_t ep,
-                  FAR uint8_t *buffer, size_t buflen);
+                      FAR uint8_t *buffer, size_t buflen);
 
   /* Process a request to handle a transfer asynchronously.  This method
    * will enqueue the transfer request and return immediately.  Only one